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2022, Vol. 67, No. 4　Online: 15 April 2022

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Highly efficient flexible perovskite solar cells with vacuum-assisted low-temperature annealed SnO2 electron transport layer Xiaoguo Li, Zejiao Shi, Fatemeh Behrouznejad, Mohammad Hatamvand, Xin Zhang, Yaxin Wang, Fengcai Liu, Haoliang Wang, Kai Liu, Hongliang Dong, Farhan Mudasar, Jiao Wang, Anran Yu, Yiqiang Zhan 2022, 67(4): 1-7.  DOI: 10.1016/j.jechem.2021.09.021 Abstract ( 17 )   PDF (2575KB) ( 10 )   The demand for lightweight, flexible, and high-performance portable power sources urgently requires high-efficiency and stable flexible solar cells. In the case of perovskite solar cells (PSCs), most of the com- mon electron transport layer (ETL) needs to be annealed for improving the optoelectronic properties, while conventional flexible substrates could barely stand the high temperature. Herein, a vacuum-assisted annealing SnO2 ETL at low temperature (100 °C) is utilized in flexible PSCs and achieved high effi-ciency of 20.14%. Meanwhile, the open-circuit voltage (Voc) increases from 1.07 V to 1.14 V. The flexible PSCs also show robust bending stability with 86.8% of the initial efficiency is retained after 1000 bending cycles at a bending radius of 5 mm. X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM), and contact angle measurements show that the density of oxygen vacancies, the surface rough- ness of the SnO2 layer, and film hydrophobicity are significantly increased, respectively. These improve- ments could be due to the oxygen-deficient environment in a vacuum chamber, and the rapid evaporation of solvents. The proposed vacuum-assisted low-temperature annealing method not only improves the efficiency of flexible PSCs but is also compatible and promising in the large-scale commer- cialization of flexible PSCs.

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Advancing Li-ion storage performance with hybrid vertical carbon/Ni3S2-based electrodes Neelakandan M. Santhosh, Nitheesha Shaji, Petra Stražar, Gregor Filipič, Janez Zavašnik, Chang Won Ho, Murugan Nanthagopal, Chang Woo Lee, Uroš Cvelbar 2022, 67(4): 8-18.  DOI: 10.1016/j.jechem.2021.09.034. Abstract ( 10 )   PDF (10634KB) ( 1 )   Conversion-reaction induced charge storage mechanisms of transition metal sulphides have received considerable interest in designing high-capacity electrodes for electrochemical energy storage devices. However, their low conductivity and structural degradation during cycling limit their applications as energy storage devices. A combination of different nickel sulphide phases tailored with carbon nanostruc- tures is suggested to address these limitations. Herein, a facile, two-step approach is demonstrated for fabricating a hybrid electrode, consisting of trinickel disulphide (Ni3S2) formed on a metallic Ni nanopar- ticle supported by vertical carbon nanotubes (VCN) backbone in the form Ni3S2/Ni@VCN. Ni3S2/Ni@VCN electrodes were tested as anode for lithium-ion batteries, and the electrode featured outstanding lithium- storage capabilities with a high reversible capacity (1113 mAh g 1 after 100 cycles at 100 mA g 1), excel- lent long-term cycling stability (770 mAh g 1 after 500 cycles at 200 mA g 1), and good rate capability. The resulting electrode performance is one of the best Li-ion storage capabilities in the Ni3S2-type anode materials described. A unique ‘‘broccoli-like” structure of polycrystalline Ni3S2 capped on conductive VCN backbone helps the interface storage process and boosts lithium storage performance.

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Heteroatom engineering on spiro-type hole transporting materials for perovskite solar cells Xianfu Zhang, Xuepeng Liu, Nan Wu, Rahim Ghadari, Mingyuan Han, Ying Wang, Yong Ding, Molang Cai, Zuopeng Qu, Songyuan Dai 2022, 67(4): 19-26.  DOI: 10.1016/j.jechem.2021.09.046 Abstract ( 7 )   PDF (8340KB) ( 4 )   A series of spiro-type hole transporting materials, spiro-OMeTAD, spiro-SMeTAD and spiro-OSMeTAD, with methoxy, methylsulfanyl or half methoxy and half methylsulfanyl terminal groups are designed and prepared. The impact of varied terminal groups on bulk properties, such as photophysical, electro- chemical, thermal, hole extraction, and photovoltaic performance in perovskite solar cells is investigated. It is noted that the terminal groups of the hole transporting material with half methoxy and half methyl- sulfanyl exhibit a better device performance and decreased hysteresis compared with all methoxy or methylsulfanyl counterparts due to better film-forming ability and improved hole extraction capability. Promisingly, the spiro-OSMeTAD also shows comparable performance than high-purity commercial spiro-OMeTAD. Moreover, the highest power conversion efficiency of the optimized device employing spiro-OSMeTAD exceeding 20% has been achieved.

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Heterostructure of Ta3N5 nanorods and CaTaO2N nanosheets fabricated using a precursor template to boost water splitting under visible light Yanpei Luo, Hao Li, Yaling Luo, Zheng Li, Yu Qi, Fuxiang Zhang, Can Li 2022, 67(4): 27-33.  DOI: 10.1016/j.jechem.2021.09.025 Abstract ( 8 )   PDF (6724KB) ( 2 )   Fabrication of heterostructure composed of one-dimensional (1D) and 2D semiconductors has inspired extensive interest in promoting photogenerated charge separation as well as performances of solar fuel production, but it is still challenging for (oxy)nitride photocatalysts due to their uncontrollable ammonia thermal preparative process. In this work, we report a synthesis on heterostructure of Ta3N5 nanorods and CaTaO2N (CTON) nanosheets (denoted as Ta3N5/CTON) by directly nitriding a 2D Dion-Jacobson (DJ) type of perovskite KCa2Ta3O10 (KCTO) precursor under the assistance of K2CO3 flux. It is demon- strated that the 2D morphology of KCTO can be well inherited to get 2D CTON, and the Ta-rich (non- stoichiometric ratio of Ca:Ta compared to CTON) feature of the KCTO as well as the easy evaporation of K species results in the formation of 1D Ta3N5 nanorods. Meanwhile, the formation of intermediate species K2Ca2Ta3O9N owning similar crystal lattice as Ta3N5 was detected and deduced to be responsible for the generation of Ta3N5 nanorods and observation of intimate interface between CTON and Ta3N5. Benefitting from the formation of special 1D/2D type-II heterostructure, obviously promoted charge sep- aration as well as photocatalytic water splitting performance can be obtained. Extended discussion demonstrates the generality of the hard-template preparative strategy developed here. To our knowl- edge, this should be the first fabrication of 1D/2D heterostructure for the (oxy)nitride semiconductors, and the developed hard-template strategy may provide an alternative way of fabricating heterostructures of other semiconductors prepared at high temperature.

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Parameter-independent error correction for potential measurements by reference electrode in lithium-ion batteries Yalun Li, Xinlei Gao, Xuning Feng, Xuebing Han, Jiuyu Du, Languang Lu, Minggao Ouyang 2022, 67(4): 34-45.  DOI: 10.1016/j.jechem.2021.09.006 Abstract ( 11 )   PDF (10661KB) ( 4 )   The safety monitoring of lithium-ion batteries (LIBs) is of great significance for realizing all-climate and full-lifespan battery management. In-situ measurement of anode potential with implanted reference electrodes (REs) has proven to be effective to monitor and avoid the occurrence of severe side reactions like Li plating to ensure the safe and fast charging. However, the intrinsic measurement errors caused by local blocking effects, which also can be referred to as potential artefacts, are seldom taken into consid- eration in existing studies, yet they highly dominate the correctness of conclusions inferred from REs. In this study, aiming at exploring the physical origin of the measurement errors and ensure reliable poten- tial monitoring, electrochemical and post-mortem tests are conducted using commercial pouch cells with implanted REs. Corresponding electrochemical model which describes the blocking effects, is established to validate the abnormal absence of lithium plating that predicted by measured anode potentials under various charging rates. Theoretical derivation is further presented to explain the error sources, which can be attributed to increased local liquid potential of the RE position. Most importantly, with the guidance of error analysis, a novel parameter-independent error correction method for RE measurements is proposed for the first time, which is proven to be adequate to estimate the real anode potentials and deduce the critical C-rate of Li plating with extra safety margin. After error correction, the resulting critical C-rates are all within the range of 0.55 ±; 0.03C, which is close to the C-rate of 0.6-0.7C obtained from experi- ments. In addition, this error correction method can be performed conveniently with only some simple RE measurements of polarization voltages, totally independent of battery electrochemical and geometric parameters. This study provides highly practical error correction method for RE measurements in real LIBs, substantially facilitating the fast diagnosis and safety evaluation of Li plating during charging of LIBs.

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Atomic insights of electronic states engineering of GaN nanowires by Cu cation substitution for highly efficient lithium ion battery Zhenjiang Li, Kesheng Gao, Ying Han, Shiqi Ding, Yanglansen Cui, Minmin Hu, Jian Zhao, Meng Zhang, Alan Meng, Jimmy Yun, Zhiming Liu, Da-Wei Wang, Changlong Sun 2022, 67(4): 46-54.  DOI: 10.1016/j.jechem.2021.09.007 Abstract ( 9 )   PDF (7158KB) ( 3 )   Electronic engineering of gallium nitride (GaN) is critical for enhancement of its electrode performance. In this work, copper (Cu) cation substituted GaN (Cu-GaN) nanowires were fabricated to understand the electronically engineered electrochemical performance for Li ion storage. Cu cation substitution was revealed at atomic level by combination of X-ray photoelectron spectroscopy (XPS), X-ray absorption fine structure (XAFS), density functional theory (DFT) simulation, and so forth. The Cu-GaN electrode deliv- ered high capacity of 813.2 mA h g 1 at 0.1 A g 1 after 200 cycles, increased by 66% relative to the unsub- stituted GaN electrode. After 2000 cycles at 10 A g 1, the reversible capacity was still maintained at 326.7 mA h g 1. The DFT calculations revealed that Cu substitution introduced the impurity electronic states and efficient interatomic electron migration, which can enhance the charge transfer efficiency and reduce the Li ion adsorption energy on the Cu-GaN electrode. The ex-situ SEM, TEM, HRTEM, and SAED analyses demonstrated the reversible intercalation Li ion storage mechanism and good structural stability. The concept of atomic-arrangement-assisted electronic engineering strategy is anticipated to open up opportunities for advanced energy storage applications.

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Adjusting the solvation structure with tris(trimethylsilyl)borate additive to improve the performance of LNCM half cells Jie Wang, Hong Dong, Peng Wang, Xiao-Lan Fu, Ning-Shuang Zhang, Dong-Ni Zhao, Shi-You Li, Xiao-Ling Cui 2022, 67(4): 55-64.  DOI: 10.1016/j.jechem.2021.09.022 Abstract ( 31 )   PDF (6715KB) ( 16 )   Tris(trimethylsilyl)borate (TMSB) has been intensively studied to improve the performances of lithium-ion batteries. However, it is still an interesting issue needed to be resolved for the research on the Li+ solvation structure affected by TMSB additive. Herein, the electrochemical tests, quantum chemistry calculations, potential-resolved in-situ electrochemical impedance spectroscopy measurements and surface analyses were used to explore the effects of Li+ solvation structure with TMSB additive on the formation of the cathode electrolyte interface (CEI) film in LiNi0.8Co0.1Mn0.1O2/Li half cells. The results reveal that the TMSB additive is easy to complex with Li+ ion, thus weaken the intermolecular force between Li+ ions and ethylene carbonate solvent, which is benefit for the cycle performance. Besides, the changed Li+ solvation structure results in a thin and dense CEI film containing compounds with Si-O and B-O bonds which is favorable to the transfer of Li+ ions. As a result, the performances of the LNCM811/Li half cells are effectively improved. This research provides a new idea to construct a high-performance CEI film by adjusting the Li+ solvation structures.

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Defect suppression and energy level alignment in formamidinium-based perovskite solar cells Yi Wang, Xiaobing Wang, Chenhui Wang, Renying Cheng, Lanxin Zhao, Xu Wang, Xuewen Zhang, Jingzhi Shang, Huang Zhang, Lichen Zhao, Yongguang Tu, Wei Huang 2022, 67(4): 65-72.  DOI: 10.1016/j.jechem.2021.09.043 Abstract ( 3 )   PDF (6101KB) ( 2 )   The vast majority of high-performance perovskite solar cells (PSCs) are based on a formamidinium lead iodide (FAPbI3)-dominant composition. Nevertheless, the FA-based perovskite films suffer from undesirable phase transition and defects-induced non-ideal interfacial recombination, which significantly induces energy loss and hinders the improvement of device performance. Herein, we employed 4-fluorophenylmethylammonium iodide (F-PMAI) to modulate surface structure and energy level alignment of the FA-based perovskite films. The superior optoelectronic films were obtained with reduced trap density, pure α-phase FAPbI3 and favorable energy band bending. The lifetime of photogenerated charge carriers increased from 489.3 ns to 1010.6 ns, and a more “p-type” perovskite film was obtained by the post-treatment with F-PMAI. Following this strategy, we demonstrated an improved power conversion efficiency of 22.59% for the FA-based PSCs with an open-circuit voltage loss of 399 mV.

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Bidirectionally catalytic polysulfide conversion by high-conductive metal carbides for lithium-sulfur batteries Genlin Liu, Cheng Yuan, Pan Zeng, Chen Cheng, Tianran Yan, Kehua Dai, Jing Mao, Liang Zhang 2022, 67(4): 73-81.  DOI: 10.1016/j.jechem.2021.09.035 Abstract ( 6 )   PDF (4797KB) ( 2 )   Utilizing catalysts to accelerate the redox kinetics of lithium polysulfides (LiPSs) is a promising strategy to alleviate the shuttle effect of lithium-sulfur (Li-S) batteries. Nevertheless, most of the reported catalysts are only effective for LiPSs reduction, resulting in the devitalization of catalysts over extended cycles as a consequence of the continuous accumulation of Li2S passivation layer. The situation gets even worse when employing mono-directional catalyst with poor electron conductivity because the charge transfer for the decomposition of solid Li2S is severely hampered. Herein, a high-conductive and dual-directional catalyst Co3C decorated on porous nitrogen-doped graphene-like structure and carbon nanotube (Co3C@PNGr-CNT) is fabricated as sulfur host, which not only promotes the precipitation of Li2S from LiPSs during discharge but also facilitates the decomposition of Li2S during subsequent charge, as evidenced by the reduced activation energies for both reduction and oxidation processes. Furthermore, the long-term catalytic stability of Co3C is corroborated by the reversible evolution of Co-C bond length over extended cycles as observed from X-ray absorption fine structure results. As a consequence, the fabricated Co3C@PNGr-CNT/S cathode delivers a low capacity decay of 0.043% per cycle over 1000 cycles at 2C. Even at high sulfur loading (15.6 mg cm-2) and low electrolyte/sulfur (E/S) ratio (∼8 μL mg-1) conditions, the battery still delivers an outstanding areal capacity of 11.05 mAh cm-2 after 40 cycles. This work provides a rational strategy for designing high-efficient bidirectional catalyst with single component for high-performance Li-S batteries.

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Dual-modification of manganese oxide by heterostructure and cation pre-intercalation for high-rate and stable zinc-ion storage Song Wang, Weibing Ma, Zhiyuan Sang, Feng Hou, Wenping Si, Jingdong Guo, Ji Liang, De’an Yang 2022, 67(4): 82-91.  DOI: 10.1016/j.jechem.2021.09.042 Abstract ( 9 )   PDF (14882KB) ( 1 )   Zinc-ion batteries (ZIBs) possess great advantages in terms of high safety and low cost, and are regarded as promising alternatives to lithium-ion batteries (LIBs). However, limited by the electrochemical kinetics and structural stability of the typical cathode materials, it is still difficult to simultaneously achieve high rates and high cycling stability for ZIBs. Herein, we present a manganese oxide (SnxMnO2/SnO2) material that is dual-modified by SnO2/MnO2 heterostructures and pre-intercalated Sn4+ cations as the cathode material for ZIBs. Such modification provides sufficient hetero-interfaces and expanded interlayer spacing in the material, which greatly facilitates the insertion/extraction of Zn2+. Meanwhile, the “structural pillars” of Sn4+ cations and the “pinning effect” of SnO2 also structurally stabilizes the MnO2 species during the repeated Zn2+ insertion/extraction, leading to ultra-high cycling stability. Due to these merits, the SnxMnO2/SnO2 cathode exhibits a high reversible capacity of 316.1 mAh g-1 at 0.3 A g-1, superior rate capability of 179.4 mAh g-1 at 2 A g-1, and 92.4% capacity retention after 2000 cycles. Consequently, this work would provide a promising yet efficient strategy by combining heterostructures and cations pre-intercalation to obtain high-performance cathodes for ZIBs.

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Fe saponite, a layered silicate for reversible lithium-ions storage with large diffusion coefficient Jian Zhang, Qing Yin, Yunjia Wu, Shuoxiao Zhang, Kai-Jie Wang, Jingbin Han 2022, 67(4): 92-100.  DOI: 10.1016/j.jechem.2021.10.007 Abstract ( 5 )   PDF (11523KB) ( 4 )   A kind of layered Li2MSiO4 material, Fe saponite with Na+ pillaring (Na+-FSAP) was developed as a low-cost and environment-friendly lithium-ion storage material. The Na+-FSAP follows the insertion/deinsertion working mechanism accompanied by valence change of Fe from Fe1.86+ to Fe2.71+ (average value) after stabilization, and displays a specific capacity of 125 mAh g-1 at 50 mA g-1 with retention ratio of 80.8% after 75 cycles. The Na+-pillaring effect and abundant structural water in the gallery urge Li+ migrate rapidly, resulting in a large Li+ diffusion coefficient within a range of 10-6.5-10-7.5 cm2 s-1. Thus, the Na+-FSAP provides a model material to design electrode materials with rapid lithium-ion migration and has great potential to take place of polyanionic-type Li2MSiO4 (M = Mn, Fe, Co) cathode materials.

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Recent progress on bimetallic NiCo and CoFe based electrocatalysts for alkaline oxygen evolution reaction: A review Gebrehiwet Abrham Gebreslase, Maria Victoria Martínez-Huerta, Maria Jesus Lázaro 2022, 67(4): 101-137.  DOI: 10.1016/j.jechem.2021.10.009 Abstract ( 17 )   PDF (14757KB) ( 3 )   The deployment of hydrogen as an energy carrier is found to be a vital alternative fuel for the future. It is expected that water electrolysis, powered by renewable energy sources, be able to scale‐up hydrogen production. However, the reaction kinetic of oxygen evolution reaction (OER) is a sluggish process, which predominantly limits the efficiency of water electrolysis. This review recapitulates the recent progress and efforts made in the design and development of two selected earth-abundant bimetallic electrocatalysts (NiCo and CoFe) for alkaline OER. Each bimetal electrocatalyst is thoroughly outlined and discussed in five sub-sections, including bimetal (oxy) hydroxides, Layered double hydroxides (LDHs) structures, oxides, composites, alloy and nanostructured electrocatalysts, and assembled with heteroatoms. Furthermore, a brief introduction to an in situ/operando characterization techniques and advantages for monitoring the structure of the electrocatalysts is provided. Finally, a summary outlining the challenges and conceivable approaches to advance OER performance is highlighted and discussed.

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UV light absorbers executing synergistic effects of passivating defects and improving photostability for efficient perovskite photovoltaics Jiale Li, Wenjing Qi, Yameng Li, Sumin Jiao, Hao Ling, Peng Wang, Xin Zhou, Khumal Sohail, Guangcai Wang, Guofu Hou, Jingshan Luo, Ying Zhao, Liming Ding, Yuelong Li, Xiaodan Zhang 2022, 67(4): 138-146.  DOI: 10.1016/j.jechem.2021.09.027 Abstract ( 7 )   PDF (6296KB) ( 3 )   Metal halide perovskite-based solar cells (PSCs) have rapidly-increased power conversion efficiency (PCE) exceeding 25% but poor stability especially under ultraviolet (UV) light. Meanwhile, non-radiative recombination caused by diverse defects in perovskite absorbers and related interfaces is one of the major factors confining further development of PSCs. In this study, we systematically investigate the role of 2-(2-hydroxy-5-methylphenyl)benzotriazole (UVP) additive in perovskite layers. By adjusting the amount of doped UVP, the quality of perovskite absorbers is significantly improved with enlarged grains, longer lifetime and diffusion length of charge carriers. Furthermore, UVP not only reduces defects for less non-radiative recombination, but also matches energy level alignment for efficient interfacial charge extraction. X-ray photoelectron spectroscopy confirms that N-donor of UVP molecule coordinates with undercoordinated Pb2+ on the surface. Interestingly, UVP incorporated in PbI2 protects the perovskite by absorbing UV through the opening and closing of the chelating ring. Eventually, the UVP treated PSCs obtain a champion PCE of 22.46% with remarkably enhanced UV stability, retaining over 90% of initial PCE after 60 mW/cm2 strong UV irradiation for 9 h while the control maintaining only 74%. These results demonstrate a promising strategy fabricating passivated and UV-resistant perovskite materials simultaneously for efficient and stable perovskite photovoltaics.

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Construction of N-doped carbon frames anchored with Co single atoms and Co nanoparticles as robust electrocatalyst for hydrogen evolution in the entire pH range Minmin Wang, Min Li, Yilin Zhao, Naiyou Shi, Hui Zhang, Yuxue Zhao, Yaru Zhang, Haoran Zhang, Wenhong Wang, Kaian Sun, Yuan Pan, Shoujie Liu, Houyu Zhu, Wenyue Guo, Yanpeng Li, Yunqi Liu, Chenguang Liu 2022, 67(4): 147-156.  DOI: 10.1016/j.jechem.2021.09.037 Abstract ( 12 )   PDF (7145KB) ( 4 )   The development of low-cost, efficient, and high atomic economy electrocatalysts for hydrogen evolution reaction (HER) in the entire pH range for sustainable hydrogen production is of great importance but still challenging. Herein, we synthesize a highly dispersed N-doped carbon frames (NCFs) anchored with Co single atoms (SAs) and Co nanoparticles (NPs) catalyst by a doping-adsorption-pyrolysis strategy for electrocatalytic hydrogen evolution. The Co SAs-Co NPs/NCFs catalyst exhibits an excellent HER activity with small overpotential, low Tafel slope, high turnover frequency as well as remarkable stability. It also exhibits a superior HER performance in the entire pH range. Combining with experimental and theoretical calculation, we find that Co SAs with Co-N3 coordination structure and Co NPs have a strong interaction for promoting synergistic HER electrocatalytic process. The H2O molecule is easily activated and dissociated on Co NPs, while the generated H* is easily adsorbed on Co SAs for HER, which makes the Co SAs-Co NPs/NCFs catalyst exhibit more suitable H adsorption strength and more conducive to the activation and dissociation of H2O molecules. This work not only proposes a novel idea for constructing coupling catalyst with atomic-level precision, but also provides strong reference for the development of high-efficiency HER electrocatalysts for practical application.

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Semi-interpenetrating-network all-solid-state polymer electrolyte with liquid crystal constructing efficient ion transport channels for flexible solid lithium-metal batteries Qinghui Zeng, Yu Lu, Pingping Chen, Zhenfeng Li, Xin Wen, Wen Wen, Yu Liu, Shuping Zhang, Hailei Zhao, Henghui Zhou, Zhi-xiang Wang, Liaoyun Zhang 2022, 67(4): 157-167.  DOI: 10.1016/j.jechem.2021.09.040 Abstract ( 7 )   PDF (12297KB) ( 3 )   The development of the solid-state polymer electrolytes (SPEs) for Li-ion batteries (LIBs) can effectively address the hidden safety issues of commercially used liquid electrolytes. Nevertheless, the unsatisfactory room temperature ion conductivity and inferior mechanical strength for linear PEO-based SPEs are still the immense obstacles impeding the further applications of SPEs for large-scale commercialization. Herein, we fabricate a series of semi-interpenetrating-network (semi-IPN) polymer electrolytes based on a novel liquid crystal (C6M LC) and poly(ethylene glycol) diglycidyl ether (PEGDE) via UV-irradiation at the first time. The LCs not only highly improve the mechanical properties of electrolyte membranes via the construction of network structure with PEGDE, but also create stable ion transport channels for ion conduction. As a result, a free-standing flexible SPE shows outstanding ionic conductivity (5.93 × 10-5 S cm-1 at 30 °C), a very wide electrochemical stability window of 5.5 V, and excellent thermal stability at thermal decomposition temperatures above 360 °C as well as the capacity of suppressing lithium dendrite growth. Moreover, the LiFePO4/Li battery assembled with the semi-IPN electrolyte membranes exhibits good cycle performance and admirable reversible specific capacity. This work highlights the obvious advantages of LCs applied to the electrolyte for the advanced solid lithium battery.

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Engineering titanium oxide-based support for electrocatalysis Ke Chen, Tao Shen, Yun Lu, Yezhou Hu, Jingyu Wang, Jian Zhang, Deli Wang 2022, 67(4): 168-183.  DOI: 10.1016/j.jechem.2021.09.048 Abstract ( 9 )   PDF (18417KB) ( 3 )   The corrosion and weaker interaction with metal catalysts of common carbon supports during electrocatalysis push the development of alternative supports materials. Titanium oxide-based materials have been widely explored as electrocatalysts supports in consideration of their chemical stability, strong interactions with metal catalyst and wider applications in electrocatalytic reactions as well as the improved electronic conductivity. This review summarizes recent research advances in engineering titanium oxide-based supports for the catalysts in electrocatalysis field to provide guidance for designing high performance non-carbon supported electrocatalysts. Typically, the titanium oxide-based supports are classified into shaped TiO2, doped TiO2, titanium suboxide and TiO2-carbon composites according to the modification methods and corresponding preparation methods. Then the engineering strategies and electrocatalytic applications are discussed in detail. Finally, the challenges, future research directions and perspectives of titanium oxide-based supports for electrocatalysis are presented for practical applications.

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Construction of bifunctional single-atom catalysts on the optimized β-Mo2C surface for highly selective hydrogenation of CO2 into ethanol Xue Ye, Junguo Ma, Wenguang Yu, Xiaoli Pan, Chongya Yang, Chang Wang, Qinggang Liu, Yanqiang Huang 2022, 67(4): 184-192.  DOI: 10.1016/j.jechem.2021.10.017 Abstract ( 6 )   PDF (8467KB) ( 3 )   Green and economical CO2 utilization is significant for CO2 emission reduction and energy development. Here, the 1D Mo2C nanowires with dominant (101) crystal surfaces were modified by the deposition of atomic functional components Rh and K. While unmodified βMo2C could only convert CO2 to methanol, the designed catalyst of K0.2Rh0.2/β-Mo2C exhibited up to 72.1% of ethanol selectivity at 150 °C. It was observed that the atomically dispersed Rh could form the bifunctional active centres with the active carrier βMo2C with the synergistic effects to achieve highly specific controlled C-C coupling. By promoting the CO2 adsorption and activation, the introduction of an alkali metal (K) mainly regulated the balanced performance of the two active centres, which in turn improved the hydrogenation selectivity. Overall, the controlled modification of βMo2C provides a new design strategy for the highly efficient, low-temperature hydrogenation of CO2 to ethanol with single-atom catalysts, which provides an excellent example for the rational design of the complex catalysts.

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POE enhanced stabilities of CsPbX3 (X = Br, I) perovskite and their white LED application Enrou Mei, Jiaming Li, Qingyun He, Yao Tong, Ruowang Liu, Hongbin Fan, Xiaojuan Liang, Weidong Xiang 2022, 67(4): 193-200.  DOI: 10.1016/j.jechem.2021.10.005 Abstract ( 3 )   PDF (5714KB) ( 2 )   Perovskite has received extensive attention due to its excellent properties, just like photoelectric, while the instability has always troubled us to the wide application of perovskite materials. Herein, we proposed to use SiO2 and POE to encapsulate perovskite nanocrystals (PNCs). In this work, we have successfully prepared a series of perovskite composite materials and films with different concentration ratios. Due to the protection of POE, the luminous intensity of CsPbBr3@POE composite film remained above 90% after stayed in the water for 42 days. The lead concentration of CsPbBr3@POE composite film was 0.8 μg/mL after 48 h of immersing in deionized water. Namely, packaging PNCs in POE could effectively prevent Pb from overflowing reduce Pb pollution. Besides, the composite films showed a wide colour gamut with 117% of NTSC colour gamut, which shows that this composite material has a development prospect in the WLED field.

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“Coffee ring” controlment in spray prepared >19% efficiency Cs0.19FA0.81PbI2.5Br0.5 perovskite solar cells Xinxin Yu, Jing Li, Yanping Mo, Tianxing Xiang, Zhiliang Ku, Fuzhi Huang, Fei Long, Yong Peng, Yi-Bing Cheng 2022, 67(4): 201-208.  DOI: 10.1016/j.jechem.2021.09.032 Abstract ( 5 )   PDF (8269KB) ( 2 )   Achieving high-quality perovskite films with uniform morphology and homogeneous crystallinity is challenging owing to the coffee ring effect (CRE) in the spray-coating technologies. In this study, an evaporation/spray-coating two-step deposition method is used to fabricate Cs0.19FA0.81PbI2.5Br0.5 light harvesters for perovskite solar cells (PSCs). Considering the solid-liquid reaction, we establish a reaction-dependent regulating strategy that inhibits CRE successfully and prepare a high-quality perovskite layer, wherein the solvent for the FAI/Br solution during the spraying process is changed from isopropanol to n-butyl alcohol (NBA). The retarded-drying-enhanced spreading of the NBA solution inhibits contact line pinning to suppress the capillary flows and increases the reaction between metal halides (CsI/PbI2) and organic salts (FAI/Br), which result in a reduction in the accumulation of solutes in the periphery effectively inhibiting CRE. Consequently, we obtain a high performance Cs0.19FA0.81PbI2.5Br0.5 PSC with a power conversion efficiency (PCE) of 19.17%. An enlarged perovskite film (10 × 10 cm2) containing 40 sub-cells is prepared. The average PCE of these devices is 18.33 ± 0.56%, proving the reliability of the “coffee ring” regulating strategy. This study provides an effective approach for CRE controlment in spraying technology to achieve high repeatability devices with good performance.

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Time-frequency analysis of Li solid-phase diffusion in spherical active particles under typical discharge modes Qiu-An Huang, Yuxuan Bai, Liang Wang, Juan Wang, Fangzhou Zhang, Linlin Wang, Xifei Li, Jiujun Zhang 2022, 67(4): 209-224.  DOI: 10.1016/j.jechem.2021.09.039 Abstract ( 5 )   PDF (2412KB) ( 2 )   Li transient concentration distribution in spherical active material particles can affect the maximum power density and the safe operating regime of the electric vehicles (EVs). On one hand, the quasi-exact/exact solution obtained in the time/frequency domain is time-consuming and just as a reference value for approximate solutions; on the other hand, calculation errors and application range of approximate solutions not only rely on approximate algorithms but also on discharge modes. For the purpose to track the transient dynamics for Li solid-phase diffusion in spherical active particles with a tolerable error range and for a wide applicable range, it is necessary to choose optimal approximate algorithms in terms of discharge modes and the nature of active material particles. In this study, approximation methods, such as diffusion length method, polynomial profile approximation method, Padé approximation method, pseudo steady state method, eigenfunction-based Galerkin collocation method, and separation of variables method for solving Li solid-phase diffusion in spherical active particles are compared from calculation fundamentals to algorithm implementation. Furthermore, these approximate solutions are quantitatively compared to the quasi-exact/exact solution in the time/frequency domain under typical discharge modes, i.e., start-up, slow-down, and speed-up. The results obtained from the viewpoint of time-frequency analysis offer a theoretical foundation on how to track Li transient concentration profile in spherical active particles with a high precision and for a wide application range. In turn, optimal solutions of Li solid diffusion equations for spherical active particles can improve the reliability in predicting safe operating regime and estimating maximum power for automotive batteries.

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Aqueous Zn-MnO2 battery: Approaching the energy storage limit with deep Zn2+ pre-intercalation and revealing the ions insertion/extraction mechanisms Yaxiong Zhang, Xiaosha Cui, Yupeng Liu, Situo Cheng, Peng Cui, Yin Wu, Zhenheng Sun, Zhipeng Shao, Jiecai Fu, Erqing Xie 2022, 67(4): 225-232.  DOI: 10.1016/j.jechem.2021.09.038 Abstract ( 9 )   PDF (6817KB) ( 5 )   Rechargeable aqueous zinc ion batteries (AZIBs) were considered as one of the most promising candidates for large-scale energy storage due to the merits of high safety and inexpensiveness. As AZIBs cathode material, MnO2 possesses great merits but was greatly hindered due to the sluggish diffusion kinetic of Zn2+ during electrochemical operations. Herein, deep Zn2+ ions intercalated δ-MnO2 (Zn-MnO2) was achieved by the in situ electrochemical deposition route, which significantly enhanced the diffusion ability of Zn2+ due to the synergistic effects of Zn2+ pillars and structural H2O. The resultant Zn-MnO2 based AZIBs delivers a record capacity of 696 mAh/g (0.5 mAh/cm2) based on the initial mass loading, which is approaching the theoretical capacity of MnO2 with a two-electrons reaction. In-situ Raman studies reveal highly reversible Zn2+ ions insertion/extraction behaviors and here the Zn-MnO2 plays the role of a container during the charge-discharge process. Further charge storage mechanism investigations point out the insertion/extraction of Zn2+ and H+ coincides, and such process is significantly facilitated results from superior interlayered configurations of Zn-MnO2. The excellent electrochemical performance of Zn-MnO2 achieved in this work suggests the deep ions pre-intercalation strategy may aid in the future development of advanced cathodes for AZIBs.

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Paired-Pd(II) centers embedded in HKUST-1 framework: Tuning the selectivity from dimethyl carbonate to dimethyl oxalate Hong-Zi Tan, Zhe-Ning Chen, Kai-Qiang Jing, Jing Sun, Yu-Ping Xu, Ning-Ning Zhang, Zhong-Ning Xu, Guo-Cong Guo 2022, 67(4): 233-240.  DOI: 10.1016/j.jechem.2021.09.033 Abstract ( 4 )   PDF (3018KB) ( 3 )   CO oxidative coupling to dimethyl oxalate (DMO) is the most crucial step in coal to ethylene glycol. Pd-based supported catalysts have been verified effective for generating DMO, but concomitant generation of dimethyl carbonate (DMC) is always unavoidable. It is generally accepted that Pd(0) is the active species for producing DMO, while Pd(II) for DMC. However, density functional theory calculations have proposed that the selectivity to DMO or DMC highly depends on the space state of Pd species rather than its oxidative state. It is thus urgently desired to develop high-efficient catalysts with well-defined structure, and further to elucidate the structure-performance relationship. In this work, HKUST-1 with unique structure of paired-Cu(II) centers was chosen as ideal support to construct the catalysts with respective paired-Pd(II) centers and isolated-Pd(II) centers via in situ Pd species doping. In despite of featuring Pdδ+ (δ≈2) oxidation state, the synthesized paired-Pd(II)/HKUST-1 catalyst still exhibited DMO as dominant product (90.8% of DMO selectivity). For isolated-Pd(II)/HKUST-1 catalyst, however, the main product was DMC (84.8% of DMC selectivity). Based on catalyst characterizations, the structures of paired-Pd(II) centers and isolated-Pd(II) centers were determined. DMO was generated from the coupling of adjacent *COOCH3 intermediates adsorbed on paired-Pd(II) centers, while DMC was produced from the reaction between methyl nitrite and the *COOCH3 intermediates formed on isolated-Pd(II) centers. Current work is the first MOFs-based catalyst with well-defined structure being applied in CO oxidative coupling reaction, which not only sheds light on the structure-performance relationship, but also inspires the potential of using MOFs as tunable platform to design high-efficient catalysts in heterogeneous catalysis.

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Boosting the water gas shift reaction on Pt/CeO2-based nanocatalysts by compositional modification: Support doping versus bimetallic alloying Kun Yuan, Xiao-Chen Sun, Hai-Jing Yin, Liang Zhou, Hai-Chao Liu, Chun-Hua Yan, Ya-Wen Zhang 2022, 67(4): 241-249.  DOI: 10.1016/j.jechem.2021.10.006 Abstract ( 7 )   PDF (9546KB) ( 2 )   The water gas shift reaction is of vital significance for the generation and transition of energy due to the application in hydrogen production and industries such as ammonia synthesis and fuel cells. The influence of support doping and bimetallic alloying on the catalytic performance of Pt/CeO2-based nanocatalysts in water gas shift reaction was reported in this work. Various lanthanide ions and 3d transition metals were respectively introduced into the CeO2 support or Pt to form Pt/CeO2:Ln (Ln = La, Nd, Gd, Tb, Yb) and PtM/CeO2 (M = Fe, Co, Ni) nanocatalysts. The sample of Pt/CeO2:Tb showed the highest activity (TOF at 200 °C = 0.051 s-1) among the Pt/CeO2:Ln and the undoped Pt/CeO2 catalysts. Besides, the sample of PtFe/CeO2 exhibited the highest activity (TOF at 200 °C = 0.12 s-1) among PtM/CeO2 catalysts. The results of the multiple characterizations indicated that the catalytic activity of Pt/CeO2:Ln catalysts was closely correlated with the amount of oxygen vacancies in doped ceria support. However, the different activity of PtM/CeO2 bimetallic catalysts was owing to the various Pt oxidation states of the bimetals dispersed on ceria. The study of the reaction pathway indicated that both the samples of Pt/CeO2 and Pt/CeO2:Tb catalyzed the reaction through the formate pathway, and the enhanced activity of the latter derived from the increased concentration of oxygen vacancies along with promoted water dissociation. As for the sample of PtFe/CeO2, its catalytic mechanism was the carboxyl route with a higher reaction rate due to the moderate valence of Pt along with improved CO activation.

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A perspective on the PGM-free metal-nitrogen-carbon catalysts for PEMFC Mingze Sun, Shuyan Gong, Yu-Xiao Zhang, Zhiqiang Niu 2022, 67(4): 250-254.  DOI: 10.1016/j.jechem.2021.10.014 Abstract ( 9 )   PDF (1728KB) ( 6 )

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In-situ determination of onset lithium plating for safe Li-ion batteries Lei Xu, Yi Yang, Ye Xiao, Wen-Long Cai, Yu-Xing Yao, Xiao-Ru Chen, Chong Yan, Hong Yuan, Jia-Qi Huang 2022, 67(4): 255-262.  DOI: 10.1016/j.jechem.2021.10.016 Abstract ( 13 )   PDF (5575KB) ( 16 )   Lithium plating in working batteries has attracted wide attention in the exploration of safe energy storage. Establishing an effective and rapid early-warning method is strongly considered but quite challenging since lithium plating behavior is determined by diverse factors. In this contribution, we present a non-destructive electrochemical detection method based on transient state analysis and three-electrode cell configuration. Through dividing the iR drop value by the current density, the as-obtained impedance quantity (Ri) can serve as a descriptor to describe the change of electrochemical reaction impedance on the graphite anode. The onset of lithium plating can be identified from the sharp drop of Ri. Once the dendritic plated lithium occurs, the extra electrochemical reactions at the lithium interfaces leads to growing active area and reduced surface resistance of the anode. We proposed a protocol to operate the batteries under the limited capacity, which renders the cell with 98.2% capacity retention after 1000 cycles without lithium plating. The early-warning method has also been validated in in-situ optical microscopy batteries and practical pouch cells, providing a general but effective method for online lithium plating detection towards safe batteries.

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Reformation of thiophene-functionalized phthalocyanine isomers for defect passivation to achieve stable and efficient perovskite solar cells Geping Qu, Danish Khan, Feini Yan, Armağan Atsay, Hui Xiao, Qian Chen, Hu Xu, Ilgın Nar, Zong-Xiang Xu 2022, 67(4): 263-275.  DOI: 10.1016/j.jechem.2021.09.041 Abstract ( 10 )   PDF (11424KB) ( 9 )   Lewis acid-base passivation is a significant technique to achieve structural stability of perovskite solar cells (PSCs) by overcoming the issues of wide grain boundaries, crystal defects, and the instability of PSCs. In this work, the combined effects of thiophene with phthalocyanine (Pc) as isomers (S2 and S3) on the photovoltaic performance of PSCs were studied for the first time. Through density functional theory calculations, we confirmed that the position of the S atom in the structure affects Lewis acid-base interactions with under-coordinated Pb2+ sites. The morphology of methylammonium lead iodide (MAPbI3) for passivated devices was improved and thin dense layers with compact surface and large grain size were observed, leading to improvement of the charge extraction ability and reduction of non-radiative recombination and the trap density. A highest power conversion efficiency of 18% was achieved for the Pc S3 passivated device, which was 6.69% more than that of the controlled device. Furthermore, the Pcs passivated devices demonstrated remarkable stability under high-moisture and high-temperature conditions.

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Advances of entropy-stabilized homologous compounds for electrochemical energy storage Xin Wang, Xiang Li, Huarong Fan, Ming Miao, Yiming Zhang, Wei Guo, Yongzhu Fu 2022, 67(4): 276-289.  DOI: 10.1016/j.jechem.2021.09.044 Abstract ( 5 )   PDF (12022KB) ( 2 )   Recently, high-entropy materials (HEMs) have gained increasing interest in the field of energy storage technology on account of their unique structural characteristics and possibilities for tailoring functional properties. Herein, the development of this class of materials for electrochemical energy storage have been reviewed, especially the fundamental understanding of entropy-dominated phase-stabilization effects and prospective applications are presented. Subsequently, critical comments of HEMs on the different aspects of battery and supercapacitor are summarized with the underlying principles for the observed properties. In addition, we also summarize their potential advantages and remaining challenges, which will ideally provide some general guidelines and principles for researchers to study and develop advanced HEMs. The diversity of material design contributed by the entropy-mediated concept provides the researchers numerous ideas of new candidates for practical applications and ensures further research in the emerging field of energy storage.

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Boosting practical high voltage lithium metal batteries by butyronitrile in ether electrolytes via coordination, hydrolysis of C≡N and relatively mild concentration strategy Jingrong Ning, Kaijia Duan, Kai Wang, Jianwen Liu, Shiquan Wang, Jiujun Zhang 2022, 67(4): 290-299.  DOI: 10.1016/j.jechem.2021.10.004 Abstract ( 2 )   PDF (9269KB) ( 2 )   Currently ether solvents have been regarded as the most compatible organic solvents with lithium metal in electrolytes of lithium batteries. However, ether solvents are unstable under high voltage (>4.0 V), and prone to side reactions with nickel-rich high-voltage cathode materials. In this work, a novel dual-solvent electrolyte in ethylene glycol dimethyl ether (DME) and butyronitrile (BN) mixed solvent was designed and fabricated for Li/LiNi0.5Mn0.3Co0.2O2-based lithium metal batteries. When charged to high voltage 4.3 V, the battery cycled in this optimal electrolyte can maintain the capacity at 133.7 mAh g-1 with a retention of 88.84% after 150 cycles at 0.2 C and -10 °C. During long-term cycling, the battery also exhibits excellent cycling performance with capacity maintained at about 112.0 mAh g-1 after 500 cycles at 1 C and -10 °C. BN has strong oxidation resistance and high conductivity, which can inhibit the decomposition of ether solvents under high voltage and improve the low temperature performance of battery effectively. Additionally, the cyano (-C≡N) group in BN molecular has a strong coordination ability with the high-valent metal ions and can mask the active ions on the cathode, correspondingly reducing the corrosion of cathode material by the electrolyte. Moreover, cyano group can participate in the hydrolysis to remove trace amounts of water and acidic by-products such as HF in the electrolyte. Therefore, the boosting effect of butyronitrile for ether solvents can provide a promising strategy for enhancing the performance of high voltage lithium metal batteries for practical industrialization.

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Surface oxidation of Ni-cermet electrodes by CO2 and H2O and how to moderate it Dingkai Chen, Mathias Barreau, Thierry Dintzer, Sylwia Turczyniak-Surdacka, Fabrice Bournel, Jean-Jacques Gallet, Spyridon Zafeiratos 2022, 67(4): 300-308.  DOI: 10.1016/j.jechem.2021.10.002 Abstract ( 5 )   PDF (4810KB) ( 2 )   The oxidation of porous Ni-yttria-stabilized zirconia (YSZ) and Ni-gadolinia-doped ceria (GDC) ceramic-metal (cermet) electrodes in H2O and CO2 atmospheres was studied by near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS). We show that the oxidation of nickel by the two gases is not similar, as is commonly believed, but it depends on the ceramic type. Nickel is vulnerable to oxidation in H2O but it resists to CO2 in Ni-GDC, as compared to the Ni-YSZ electrode. Inspired by this observation we conceptualize and fabricate Ni-YSZ electrodes modified by ceria nanoparticles, which show significantly higher resistance to CO2 oxidation as compared with conventional Ni-YSZ electrodes. The preparation of tailor-made cermet electrodes with identical bulk/mechanical characteristics but very different surface properties offers a promising fabrication strategy for high-performance and durability solid oxide electrolysis cells for CO2 conversion.

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Atomic-level insights into surface engineering of semiconductors for photocatalytic CO2 reduction Hengming Huang, Hui Song, Jiahui Kou, Chunhua Lu, Jinhua Ye 2022, 67(4): 309-341.  DOI: 10.1016/j.jechem.2021.10.015 Abstract ( 7 )   PDF (35590KB) ( 4 )   Photocatalytic conversion of CO2 into solar fuels provides a bright route for the green and sustainable development of human society. However, the realization of efficient photocatalytic CO2 reduction reaction (CO2RR) is still challenging owing to the sluggish kinetics or unfavorable thermodynamics for basic chemical processes of CO2RR, such as adsorption, activation, conversion and product desorption. To overcome these shortcomings, recent works have demonstrated that surface engineering of semiconductors, such as introducing surface vacancy, surface doping, and cocatalyst loading, serves as effective or promising strategies for improved photocatalytic CO2RR with high activity and selectivity. The essential reason lies in the activation and reaction pathways can be optimized and regulated through the reconstruction of surface atomic and electronic structures. Herein, in this review, we focus on recent research advances about rational design of semiconductor surface for photocatalytic CO2RR. The surface engineering strategies for improved CO2 adsorption, activation, and product selectivity will be reviewed. In addition, theoretical calculations along with in situ characterization techniques will be in the spotlight to clarify the kinetics and thermodynamics of the reaction process. The aim of this review is to provide deep understanding and rational guidance on the design of semiconductors for photocatalytic CO2RR.

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Synthesis and characterization of the flower-like LaxCe1 xO1.5+d catalyst for low-temperature oxidative coupling of methane Ru Feng, Pengyu Niu, Bo Hou, Qiang Wang, Litao Jia, Minggui Lin, Debao Li 2022, 67(4): 342-353.  DOI: 10.1016/j.jechem.2021.10.018 Abstract ( 6 )   PDF (7772KB) ( 4 )   Lanthanum-based oxides are promising candidates for low-temperature oxidative coupling of methane (OCM). To further lower the OCM reaction temperature, the Ce doped flower-like La2O2CO3 microsphere catalysts were synthesized, achieving a significantly low reaction temperature (375 °C) while maintaining high C2+ hydrocarbon selectivity (43.0%). Doping Ce into the lattice of La2O2CO3 created more surface oxygen vacancies and bulk lattice defects, which was in favor of the transformation and migration of oxygen species at 350-400 °C. The designed H2 temperature-programmed reduction (H2-TPR) experiments provided strong evidence that the low reaction temperature of LaxCe1-xO1.5+δ can be attributed to the transformation and migration of oxygen species, which dynamically generated surface oxygen vacancies for continuous oxygen activation to selectively convert methane. Moreover, designed temperature-programmed surface reaction (TPSR) clarified that two kinds of surface oxygen species in LaxCe1-xO1.5+δ catalysts were concerned with catalytic performance, that is, the surface chemisorbed oxygen species for the activation of CH4 and the formation of CH3• intermediates, surface La-Ce-O lattice oxygen species that caused the excessive oxidation of CH3• intermediates. Finally, the factors affecting the transformation and migration of oxygen species were explored.

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Isolated Co single atoms in nitrogen-doped graphene for aluminum- sulfur batteries with enhanced kinetic response Zhiqiu Hu, Shuai Xie, Yue Guo, Yadong Ye, Jing Zhang, Song Jin, Hengxing Ji 2022, 67(4): 354-360.  DOI: 10.1016/j.jechem.2021.10.010 Abstract ( 5 )   PDF (4962KB) ( 2 )   Al-S batteries are promising next generation energy storage devices due to their high theoretical energy density (1340 Wh kg-1), low cost, and safe operation. However, the electrochemical performance of Al-S batteries suffers poor reversibility owing to slow kinetic processes determined by the difficulty of reversible conversion between Al and S. Here, we proposed a single-atom catalysts comprising Co atoms embedded in a nitrogen-doped graphene (CoNG) as an electrochemical catalyst in the sulfur cathode that renders a reduced discharge-charge voltage hysteresis and improved sulfur utilization in the cathode. The structural and electrochemical analyses suggest that the CoNG facilitated both the formation and oxidation of AlSx during the electrochemical reactions of the sulfur species. Consequently, the CoNG-S composite can deliver a considerably reduced voltage hysteresis of 0.76 V and a reversible specific capacity of 1631 mAh g-1 at 0.2 A g-1 with a sulfur utilization of more than 97%.

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Organic additives in all-inorganic perovskite solar cells and modules: from moisture endurance to enhanced efficiency and operational stability Yameen Ahmed, Bilawal Khan, M. Bilal Faheem, Keqing Huang, Yuanji Gao, Junliang Yang 2022, 67(4): 361-390.  DOI: 10.1016/j.jechem.2021.09.047 Abstract ( 12 )   PDF (31757KB) ( 13 )   Power conversion efficiency (PCE) of perovskite solar cells (PSC) has been skyrocketed to certified 25.5% owing to their improved and tunable optoelectronic properties. Although, various strategies have been adopted to date regarding PCE and stability enhancement within PSC technology, certain instability factors (moisture, heat, light) are hindering their commercial placement. Recently, all-inorganic PSCs got hype in the photovoltaic research community after they attained PCE > 20% and due to their significant endurance against heat and light mishmashes, but there only left moisture sensitivity as the only roadblock for their industrial integration. Here, we review the recent progress of additive inclusion into all-inorganic (CsPbX3) PSCs to stabilize their intrinsic structure and to withstand the performance limiting factors. We start with the detailed description of chemical instability of different perovskite compositions, phase segregation, and how organic molecules and dyes help to repair the structural defects to improve the overall PCE and stability of PSCs. Moisture endurance as a result of chemical passivation through organic additives, low-dimensional inorganic PSCs to enhance device stability and scalable fabrication of CsPbX3 PSCs are also reviewed. The challenges of module degradation and design implications with proposed strategies and outlook are interpreted in the ending phrases of this review.

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MOFs fertilized transition-metallic single-atom electrocatalysts for highly-efficient oxygen reduction: Spreading the synthesis strategies and advanced identification Kexin Song, Yu Feng, Wei Zhang, Weitao Zheng 2022, 67(4): 391-422.  DOI: 10.1016/j.jechem.2021.10.011 Abstract ( 3 )   PDF (19018KB) ( 2 )   Metal-organic frameworks (MOFs) have been widely used in oxygen reduction reaction (ORR) of fuel cells and metal-air batteries, attributed to their unique structures and compositions. Recently, the preparation of transition-metallic single-atom electrocatalysts (TM-SACs) using MOFs as precursors or templates has made great progress. Herein, the development history of SACs prepared based on MOFs and their characterization are overviewed firstly, and then several strategies are summarized for preparing TM-SACs using MOFs and further modification. Finally, the challenges and opportunities confronted by TM-SACs are fully discussed. Consequently, our work can guide the realization of TM-SACs abundant with high activity, high loading and high stability.

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Endoplasmic-reticulum-like catalyst coating on separator to enhance polysulfides conversion for lithium-sulfur batteries Sai-Nan Xu, Teng Zhao, Li-Li Wang, Yong-Xin Huang, Yu-Sheng Ye, Nan-Xiang Zhang, Tao Feng, Li Li, Feng Wu, Ren-Jie Chen 2022, 67(4): 423-431.  DOI: 10.1016/j.jechem.2021.09.036 Abstract ( 4 )   PDF (8922KB) ( 2 )   Lithium-sulfur (Li-S) batteries with high theoretical specific energy of 2600 Wh kg-1 are one of promising candidates for next-generation energy storage devices. However, the severe shuttle effect of intermediate polysulfides leads to rapid capacity decay during battery cycling, especially at high sulfur loading and high current density. Herein, the MnO nanoparticles covered carbon with endoplasmic-reticulum-like structure (MnO@ERC) as separator coating for Li-S batteries is proposed. The MnO@ERC coating can act as upper current collector to enhance electrical conductivity of cathode and decrease the interface impedance of the whole battery. More importantly, both the polar MnO nanoparticles and Mn3O4 formed at the end of the charging process can catalyze the conversion of lithium polysulfides, which is convinced by the high adsorption energy and the elongate S-S bond. As a result, Li-S batteries based on MnO@ERC coating separator showed stable cycle for 350 cycles under 0.5C, high discharge specific capacity of 783.6 mAh g-1 after 100 cycles at 0.2 C, 534.7 mAh g-1 after 100 cycles under the sulfur loading of 5.26 mg cm-2 and low self-discharge rate of 9.1% after resting 48 h.

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Recent advances in electrocatalytic oxygen reduction for on-site hydrogen peroxide synthesis in acidic media Jun-Yu Zhang, Chuan Xia, Hao-Fan Wang, Cheng Tang 2022, 67(4): 432-450.  DOI: 10.1016/j.jechem.2021.10.013 Abstract ( 12 )   PDF (9664KB) ( 5 )   Electrocatalytic oxygen reduction reaction (ORR) via two-electron pathway is a promising approach to decentralized and on-site hydrogen peroxide (H2O2) production beyond the traditional anthraquinone process. In recent years, electrochemical H2O2 production in acidic media has attracted increasing atten- tion owing to its stronger oxidizing capacity, superior stability, and higher compatibility with various applications. Here, recent advances of H2O2 electrosynthesis in acidic media are summarized. Specifically, fundamental aspects of two-electron ORR mechanism are firstly presented with an emphasis on the pH effect on catalytic performance. Major categories of promising electrocatalysts are then reviewed, including noble-metal-based materials, non-noble-metal single-atom catalysts, non-noble- metal compounds, and metal-free carbon-based materials. The innovative development of electrochem- ical devices and in situ/on-site application of electrogenerated H2O2 are also highlighted to bridge the gap between laboratory-scale fundamental research and practically relevant H2O2 electrosynthesis. Finally, critical perspectives on present challenges and promising opportunities for future research are provided.

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Boosting selectivity and stability on Pt/BN catalysts for propane dehydrogenation via calcination & reduction-mediated strong metal-support interaction Yaoxin Wang, Jiandian Wang, Ping Zheng, Changyong Sun, Junyin Luo, Xiaowei Xie 2022, 67(4): 451-457.  DOI: 10.1016/j.jechem.2021.10.008 Abstract ( 9 )   PDF (3292KB) ( 4 )   Propane dehydrogenation (PDH) provides an alternative route for producing propylene. Herein, we demonstrates that h-BN is a promising support of Pt-based catalysts for PDH. The Pt catalysts supported on h-BN were prepared by an impregnation method using Pt(NH3)4(NO3)2 as metal precursors. It has been found that the Pt/BN catalyst undergoing calcination and reduction is highly stable in both PDH reaction and coke-burning regeneration, together with low coke deposition and outstanding propylene selectivity (99%). Detailed characterizations reveal that the high coke resistance and high propylene selectivity of the Pt/BN catalyst are derived not only from the absence of acidity on BN support, but also from the calcination-induced and reduction-adjusted strong metal-support interaction (SMSI) between Pt and BN, which causes the partial encapsulation of Pt particles by BOx overlayers. The BOx overlayers can block the low-coordinated Pt sites and constrain Pt particles into smaller ensembles, suppressing side reactions such as cracking and deep dehydrogenation. Moreover, the BOx overlayers can effectively inhi- bit Pt sintering by the spatial isolation of Pt during periodic reaction-regeneration cycles. In this work, the catalyst support for PDH is expanded to nonoxide BN, and the understanding of SMSI between Pt and BN will provide rational design strategy for BN-based catalysts.

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High efficiency and stable solid-state fiber dye-sensitized solar cells obtained using TiO2 photoanodes enhanced with metal organic frameworks Jae Ho Kim, Hyun Woo Park, Sung-Jun Koo, Daseul Lee, Eunyeong Cho, Yong-Ki Kim, Myunghun Shin, Jin Woo Choi, Hee Jung Lee, Myungkwan Song 2022, 67(4): 458-466.  DOI: 10.1016/j.jechem.2021.10.034 Abstract ( 7 )   PDF (5737KB) ( 2 )   Solid-state fiber dye-sensitized solar cells (SS-FDSSCs) have been the subject of intensive attention and development in recent years. Although this field is only in its infancy, metal-organic frameworks (MOFs) are one such material that has been utilized to further improve the power conversion efficiency of solar cells. In this study, MOF-integrated DSSCs were shown to have potential in the development of solar cell devices with efficiency comparable to or better than that of conventional solar cells. The power conversion efficiency (PCE) of SS-FDSSCs was improved by embedding MOF-801 into a mesoporous-TiO2 (mp-TiO2) layer, which was used as a photoanode in SS-FDSSCs, which are inherently flexible. The PCE of the MOF-integrated SS-FDSSCs was 6.50%, which is comparable to that of the reference devices (4.19%). The MOF-801 enhanced SS-FDSSCs decreased the series resistance (Rs) value, resulting in effective elec- tron extraction with improved short-circuit current density (JSC), while also increasing the shunt resis- tance (Rsh) value to prevent the recombination of photo-induced electrons. The result is an improved fill factor and, consequently, a higher value for the PCE.

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Regulating the growth of lithium dendrite by coating an ultra-thin layer of gold on separator for improving the fast-charging ability of graphite anode Shuaishuai Yan, Xiaoxia Chen, Pan Zhou, Peican Wang, Hangyu Zhou, Weili Zhang, Yingchun Xia, Kai Liu 2022, 67(4): 467-473.  DOI: 10.1016/j.jechem.2021.10.036 Abstract ( 8 )   PDF (5625KB) ( 12 )   With the ever-growing application of lithium-ion batteries (LIBs), their fast-charging technology has attracted great interests of scientists. However, growth of lithium dendrites during fast charge of the bat- teries with high energy density may pose great threats to the operation and cause serious safety issues. Herein, we prepared a functional separator with an ultra-thin (20 nm) layer of Au nanoparticles deposited by evaporation coating method which could regulate growth direction and morphology of the lithium dendrites, owing to nearly zero overpotential of lithium meal nucleation on lithiated Au. Once the Li den- drites are about to form on the graphite anode during fast charging (or lithiation), they plate predomi- nantly on the Au deposited separator rather than on the graphite. Such selective deposition does not compromise the electrochemical performance of batteries under normal cycling. More importantly, it enables the better cycling stability of batteries at fast charge condition. The Li/Graphite cells with Au nanoparticles coated separator could cycle stably with a high areal capacity retention of 90.5% over 95 cycles at the current density of 0.72 mA cm 2. The functional separator provides an effective strategy to adjust lithium plating position at fast charge to ensure high safety of batteries without a compromise on the energy density of LIBs.

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Selective conversion of N2 to NH3 on highly dispersed RuO2 using amphiphilic ionic liquid-anchored fibrous carbon structure Kahyun Ham, Muhammad Salman, Sunki Chung, Minjun Choi, HyungKuk Ju, Hye Jin Lee, Jaeyoung Lee 2022, 67(4): 474-482.  DOI: 10.1016/j.jechem.2021.09.004 Abstract ( 5 )   PDF (2777KB) ( 2 )   Ammonia (NH3) plays a key role in the agricultural fertilizer and commodity chemical industries and is useful for exploring hydrogen storage carriers. The electrochemical nitrogen reduction reaction (NRR) is receiving attention as an environmentally sustainable NH3 synthesis replacement for the traditional Haber–Bosch process owing to its near ambient reaction conditions (<100 C and 1 atm). However, its NH3 yield and faradaic efficiency are extremely low because of the sluggish kinetics of N N bond dissociation and the hindrance from competitive hydrogen evolution. To overcome these challenges, we herein introduce a dual-functionalized ionic liquid (1-(4-hydroxybutyl)-3-methylimidazolium hydroxide [HOBIM]OH) for a highly dispersed ruthenium oxide electrocatalyst to achieve a biased NRR. The observed uniform distribution of RuO2 on the carbon fiber and increase in the surface area for N2 adsorption by limiting proton access can be attributed to the presence of imidazolium ions. Moreover, extensive N2 adsorption contributes to enhanced NRR selectivity with an NH3 yield of 3.0 10 10 mol cm 2 s 1 (91.8 lg h 1 mg 1) and a faradaic efficiency of 2.2% at 0.20 VRHE.We expect our observations to provide new insights into the design of effective electrode structures for electrochemical NH3 synthesis.

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Constructing 3D interweaved MXene/graphitic carbon nitride nanosheets/graphene nanoarchitectures for promoted electrocatalytic hydrogen evolution Haiyan He, Yuxian Chen, Cuizhen Yang, Lu Yang, Quanguo Jiang, Huajie Huang 2022, 67(4): 483-491.  DOI: 10.1016/j.jechem.2021.10.019 Abstract ( 22 )   PDF (7039KB) ( 13 )   The technique of electrocatalytic hydrogen evolution reaction (HER) represents a development trend of clean energy generation and conversion, while the electrode catalysts are bound to be the core unit in the electrochemical HER system. Herein, we demonstrate a bottom-up approach to the construction of three-dimensional (3D) interconnected ternary nanoarchitecture originated from Ti3C2Tx MXene, graphi- tic carbon nitride nanosheets and graphene (MX/CN/RGO) through a convenient co-assembly process. By virtue of the 3D porous frameworks with ultrathin walls, large specific surface areas, optimized electronic structures, high electric conductivity, the resulting MX/CN/RGO nanoarchitecture expresses an excep- tional HER performance with a low onset potential of only 38 mV, a small Tafel slop of 76 mV dec 1 as well as long lifespan, all of which are more competitive than those of the bare Ti3C2Tx, g-C3N4, gra- phene as well as binary MX/RGO and CN/RGO electrocatalysts. Theoretical simulations further verify that the ternary MX/CN/RGO nanoarchitecture with ameliorative band structure is able to facilitate the elec- tron transport and meanwhile offer multistage catalytically active sites, thereby guaranteeing rapid HER kinetics during the electrocatalytic process.

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Scission of C-O and C-C linkages in lignin over RuRe alloy catalyst Xinxin Li, Yangming Ding, Xiaoli Pan, Yanan Xing, Bo Zhang, Xiaoyan Liu, Yuanlong Tan, Hua Wang, Changzhi Li 2022, 67(4): 492-499.  DOI: 10.1016/j.jechem.2021.10.040 Abstract ( 13 )   PDF (5855KB) ( 6 )   The performance of lignin depolymerization is basically determined by the interunit C-O and C-C bonds. Numerous C-O bond cleavage strategies have been developed, while the cleavage of C-C bond between the primary aromatic units remains a challenging task due to the high dissociation energy of C-C bond. Herein, a multifunctional RuRe alloy catalyst was designed, which exhibited exceptional catalytic activity for the cleavage of both C-O and C-C linkages in a broad range of lignin model compounds (b-1, a-5, 5-5, b-O-4, 4-O-5) and two stubborn lignins (kraft lignin and alkaline lignin), affording 97.5% overall yield of monocyclic compounds from model compounds and up to 129% of the maximum theoretical yield of monocyclic products based on C-O bonds cleavage from realistic lignin. Scanning transmission electron microscopy (STEM) characterization showed that RuRe (1:1) alloy particles with hexagonal close-packed structure were homogeneously dispersed on the support. Quasi-in situ X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS) indicate that Ru species were predominantly metallic state, whereas Re species were partially oxidized; meanwhile, there was a strong interaction between Ru and Re, where the electron transfer from Re to Ru was occurred, resulting in great improvement on the capability of C-O and C-C bonds cleavage in lignin conversion.

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Correlation between impedance spectroscopy and bubble-induced mass transport in the electrochemical reduction of carbon dioxide Stefania Lettieri, Juqin Zeng, M. Amin Farkhondehfal, Umberto Savino, Marco Fontana, Candido F. Pirri, Adriano Sacco 2022, 67(4): 500-507.  DOI: 10.1016/j.jechem.2021.10.023 Abstract ( 7 )   PDF (2709KB) ( 3 )   In the electrochemical conversion of carbon dioxide, high currents need to be employed to obtain large production rates, thus implying that mass transport of reactants and products is of crucial importance. This aspect can be investigated by employing a model that depicts the local environment for the reduc- tion reactions. Simultaneously, electrochemical impedance spectroscopy, despite being a versatile tech- nique, has rarely been adopted for studying the mass transport features during the carbon dioxide (CO2) electroreduction. In this work, this aspect is deeply analyzed by correlating the results of impedance spectroscopy characterization with those obtained by a bubble-induced mass transport modeling under controlled diffusion conditions on a gold rotating disk electrode. The effects of potential and rotation rate on the local environment are also clarified. In particular, it has been found that CO2 depletion occurs at high kinetics when the rotation is absent, giving rise to an increment of the competing hydrogen evolu- tion reaction. This feature reflects in an enlargement of the diffusion resistance, which overcomes the charge transport one.

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Recent progress and perspectives on Sb2Se3-based photocathodes for solar hydrogen production via photoelectrochemical water splitting Shuo Chen, Tianxiang Liu, Zhuanghao Zheng, Muhammad Ishaq, Guangxing Liang, Ping Fan, Tao Chen, Jiang Tang 2022, 67(4): 508-523.  DOI: 10.1016/j.jechem.2021.08.062 Abstract ( 38 )   PDF (16434KB) ( 17 )   Photoelectrochemical (PEC) cells involved with semiconductor electrodes can simultaneously absorb solar energy and perform chemical reactions, which are considered as an attractive strategy to produce renewable and clean hydrogen energy. Sb2Se3 has been widely investigated in constructing PEC photocathodes benefitting of its low toxicity, suitable band gap, superior optoelectronic properties, and outstanding photocorrosion stability. We first present a brief overview of basic concepts and principles of PEC water splitting as well as a comparison between Sb2Se3 and other numerous candidates. Then the material characteristics and preparation methods of Sb2Se3 are introduced. The development of Sb2Se3-based photocathodes in PEC water splitting with various architectures and engineering efforts (i.e., absorber engineering, interfaces engineering, co-catalyst engineering and tandem engineering) to improve solar-to-hydrogen (STH) efficiency are highlighted. Finally, we debate the possible future directions to further explore the researching fields of Sb2Se3-based photocathodes with a strongly positive outlook in PEC processed solar hydrogen production.

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Recent advances of composite electrolytes for solid-state Li batteries Laiqiang Xu, Jiayang Li, Honglei Shuai, Zheng Luo, Baowei Wang, Susu Fang, Guoqiang Zou, Hongshuai Hou, Hongjian Peng, Xiaobo Ji 2022, 67(4): 524-548.  DOI: 10.1016/j.jechem.2021.10.038 Abstract ( 8 )   PDF (13337KB) ( 7 )   All-solid-state lithium batteries (ASSLBs) are recognized as high energy density batteries system without safety issues within the next generation of batteries. The development of solid electrolytes is the crucial step of ASSLBs. The composite electrolyte has stable physical and electrochemical characteristics, and its comprehensive performance surpasses the individual solid electrolyte, bringing unique vitality to the solid electrolyte. However, their intrinsic weakness limits the development of composite electrolytes. In this review, we provide a comprehensive and in-depth understanding of the challenges and opportu- nities of composite electrolytes, with special focus on mechanisms of ion transport, nanostructure design towards high ionic conductivity, interfacial issues within electrolytes and electrodes. Furthermore, future development is prospected, which can shed light on researchers in this field and accelerate the industrial production of composite electrolytes.

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Extended X-ray absorption fine structure (EXAFS) of FAPbI3 for understanding local structure-stability relation in perovskite solar cells Dong-Ho Kang, Yong-Jun Park, Yun-Sung Jeon, Nam-Gyu Park 2022, 67(4): 549-554.  DOI: 10.1016/j.jechem.2021.10.028 Abstract ( 9 )   PDF (3105KB) ( 2 )   Perovskite solar cells (PSCs) employing formamidinium lead iodide (FAPbI3) have shown high efficiency. However, operational stability has been issued due to phase instability of a phase FAPbI3 at ambient tem-perature. Excess precursors in the perovskite precursor solution has been proposed to improve not only power conversion efficiency (PCE) but also device stability. Nevertheless, there is a controversial issue on the beneficial effect on PCE and/or stability between excess FAI and excess PbI2. We report here extended X-ray absorption fine structure (EXAFS) of FAPbI3 to study local structural change and explain the effect of excess precursors on photovoltaic performance and stability. Perovskite films prepared from the pre- cursor solution with excess PbI2 shows better stability than those from the one with excess FAI, despite similar PCE. A rapid phase transition from a phase to non-perovskite d phase is observed from the per-ovskite film formed by excess FAI. Furthermore, the (Pb-I) bond distance evaluated by the Pb LIII-edge EXAFS study is increased by excess FAI, which is responsible for the phase transition and poor device sta- bility. This work can provide important insight into local structure-stability relation in the FAPbI3-based PSCs.

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Surface defect ordered Cu2ZnSn(S,Se)4 solar cells with efficiency over 12% via manipulating local substitution Changcheng Cui, Dongxing Kou, Wenhui Zhou, Zhengji Zhou, Shengjie Yuan, Yafang Qi, Zhi Zheng, Sixin Wu 2022, 67(4): 555-562.  DOI: 10.1016/j.jechem.2021.10.035 Abstract ( 9 )   PDF (5185KB) ( 6 )   The environmentally friendly Cu2ZnSn(S,Se)4 (CZTSSe) compounds are promising direct bandgap materi- als for application in thin film solar cells, but the spontaneous surface defects disordering would lead to large open-circuit voltage deficit (Voc,deficit) and significantly limit kesterite photovoltaics performance, primarily arising from the generated more recombination centers and insufficient p to n conversion at p-n junction. Herein, we establish a surface defects ordering structure in CZTSSe system via local substi- tution of Cu by Ag to suppress disordered CuZn defects and generate benign n-type ZnAg donors. Taking advantage of the decreased annealing temperature of AgF post deposition treatment (PDT), the high con- centration of Ag incorporated into surface absorber facilitates the formation of surface ordered defect environment similar to that of efficient CIGS PV. The manipulation of highly doped surface structure could effectively reduce recombination centers, increase depletion region width and enlarge the band bending near p-n junction. As a result, the AgF-PDT device finally achieves maximum efficiency of 12.34% with enhanced Voc of 0.496 V. These results offer a new solution route in surface defects and energy-level engineering, and open the way to build up high quality p-n junction for future development of kesterite technology.

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Electrode materials for aqueous multivalent metal-ion batteries: Current status and future prospect Na Fu, Yu-Ting Xu, Shu Zhang, Qi Deng, Jun Liu, Chun-Jiao Zhou, Xiong-Wei Wu, Yu-Guo Guo, Xian-Xiang Zeng 2022, 67(4): 563-584.  DOI: 10.1016/j.jechem.2021.08.057 Abstract ( 13 )   PDF (14156KB) ( 5 )   In recent years, the pursuit of high-efficiency electrochemical storage technology, the multivalent metal- ion batteries (MIBs) based on aqueous electrolytes have been widely explored by researchers because of their safety, environmental friendliness, abundant reserves and low price, and especially the merits in energy and power densities. This review firstly expounds on the problems existing in the electrode mate- rials of aqueous multivalent MIBs (Zn2+, Mg2+, Al3+, Ca2+), from the classical inorganic materials to the emerging organic compounds, and then summarizes the design strategies in bulk and interface structure of electrodes with favorable kinetics and stable cycling performance, especially laying the emphasis on the charge storage mechanism of cathode materials and dendrite-free Zinc anode from the aspect of elec- trolyte optimization strategies, which can be extended to other aqueous multivalent MIBs. Ultimately, the possible development directions of the aqueous multivalent MIBs in the future are provided, antici- pating to provide a meaningful guideline for researchers in this area.

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An integrated approach to improve the performance of lean-electrolyte lithium-sulfur batteries Hualin Ye, Jianguo Sun, Yun Zhao, Jim Yang Lee 2022, 67(4): 585-592.  DOI: 10.1016/j.jechem.2021.11.004 Abstract ( 8 )   PDF (5823KB) ( 4 )   While the sulfur conversion reaction kinetics in Li-S batteries is nowadays improved by the use of appro- priate electrocatalysts, it remains a challenge for the batteries to perform well under the lean electrolyte condition where polysulfide shuttle, electrode passivation and the loss of electrolyte due to side reac- tions, are aggravated. These challenges are addressed in this study by the tandem use of a polysulfide conversion catalyst and a redox-targeting mediator in a gel sulfur cathode. Specifically, the gel cathode reduces the polysulfide mobility and hence the polysulfide shuttle and the passivation of the lithium anode by the crossover polysulfides. The redox mediator restrains the deposition of inactive sulfur spe- cies in the cathode thereby enabling the Fe-N and Co-N co-doped carbon catalyst to prolong its catalytic activity. Consequently, the integrated catalytic system is able to increase the discharge capacity of high-loading (6.8 mg cm-2) lean-electrolyte (4.0 mL mg-1) Li-S batteries from ~630 to ~1316 mAh g-1, con-currently with an improvement of the cycle life (600 cycles with 46% capacity retention at 1.0 mA cm-2). Redox mediator assisted catalysis in a gel cathode is therefore an effective strategy to extend the appli- cation of the sulfur conversion catalyst in lean electrolyte Li-S batteries.

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The origins of kinetics hysteresis and irreversibility of monoclinic Li3V2(PO4)3 Hua Huo, Zeyu Lin, Guiming Zhong, Shuaifeng Lou, Jiajun Wang, Yulin Ma, Changsong Dai, Yueping Xiong, Geping Yin, Yong Yang 2022, 67(4): 593-603.  DOI: 10.1016/j.jechem.2021.09.001 Abstract ( 15 )   PDF (9588KB) ( 2 )   Monoclinic Li3V2(PO4)3 is a promising cathode material with complex charge-discharge behavior. Previous structural investigation of this compound mainly focuses on local environments; while the reac- tion kinetics and the driving force of irreversibility of this material remain unclear. To fully understand the above issues, both the equilibrium and the non-equilibrium reaction routes have been systematically investigated in this study. Multiple characterization techniques including X-ray diffraction, variable tem- perature (spinning rate) and ex/in situ 7Li, 31P solid state NMR have been employed to provide compre- hensive insights into kinetics, dynamics, framework structure evolution and charge ordering, which is essential to better design and application of lithium transition metal phosphate cathodes. Our results suggest that the kinetics process between the non-equilibrium and the quasi-equilibrium delithiation pathways from Li2V2(PO4)3 to V2(PO4)3 is related with a slow relaxation from two-site to one-site delithi- ation. More importantly, it has been demonstrated that the irreversibility in this system is not solely affected by cation and/or charge ordering/disordering, but mainly driven by framework structure distortion.

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Effects of long-term fast charging on a layered cathode for lithium-ion batteries Jingwei Hu, Fengsong Fan, Qian Zhang, Shengwen Zhong, Quanxin Ma 2022, 67(4): 604-612.  DOI: 10.1016/j.jechem.2021.10.030 Abstract ( 5 )   PDF (8203KB) ( 2 )   Fast charging, which aims to shorten recharge times to 10-15 min, is crucial for electric vehicles (EVs), but battery capacity usually decays rapidly if batteries are charged under such severe conditions. Revealing the failure mechanism is a prerequisite to improving the charging performance of lithium (Li)-ion batteries. Previous studies have focused less on cathode materials while also mostly focusing on their early changes. Thus, the cumulative effect of long-term fast charging on cathode materials has not been fully studied. Here, we study the changes in a layered cathode material during 1000 cycles of 6C charging based on 1.6 Ah LiCoO2/graphite pouch cells. Postmortem analysis reveals that the surface structure, charge transfer resistance and Li-ion diffusion coefficient of the cathode degenerate during repeated fast charging, causing a large increase in polarization. This polarization-induced poor utilization of the Li inventory is an important reason for the rapid capacity fading of batteries. These findings deepen the understanding of the aging mechanism for cells undergoing fast charging and can be used as benchmarks for the future development of high-capacity, fast-charging layered cathode materials.

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Bi-salt electrolyte for aqueous rechargeable aluminum battery Yaning Gao, Yu Li, Haoyi Yang, Lumin Zheng, Ying Bai, Chuan Wu 2022, 67(4): 613-620.  DOI: 10.1016/j.jechem.2021.11.003 Abstract ( 10 )   PDF (4323KB) ( 4 )   The exertion of superior high-energy density based on multivalent ions transfer of rechargeable aluminum batteries is greatly hindered by limited electrochemical stability window of typical water in salt electrolyte (WiSE). Recently, it is reported that a second salt addition to the WiSE can offer further suppression of water activities, and achieves a much wider electrochemical window compared with aqueous WiSE electrolytes. Hence, we demonstrate a class of water in bi-salt electrolyte containing the trifluoromethanesulfonate (OTF), which exhibits an ultra-wide electrochemical window of 4.35 V and a very low overpotential of 14.6 mV. Moreover, the interface chemistry between cathode and electrolyte is also confirmed via kinetic analysis. Surprisingly, we find the electrolyte can effectively suppress Mn dissolution from the cathode, alleviate self-discharge behavior, and ensure a stable electrode-electrolyte interface based on the interface concentrated-confinement effect. Owing to these unique merits of water in bi-salt electrolyte, the AlxMnO2-nH2O material delivers a high capacity of 364 mAh g 1 and superb long-term cycling performance >; 150 cycles with a capacity decay rate of 0.37% per cycle with coulombic efficiency at ca. 95%.

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Opportunities and challenges of organic flow battery for electrochemical energy storage technology Ziming Zhao, Changkun Zhang, Xianfeng Li 2022, 67(4): 621-639.  DOI: 10.1016/j.jechem.2021.10.037 Abstract ( 7 )   PDF (12289KB) ( 2 )   For flow batteries (FBs), the current technologies are still expensive and have relatively low energy density, which limits their large-scale applications. Organic FBs (OFBs) which employ organic molecules as redox-active materials have been considered as one of the promising technologies for achieving low- cost and high-performance. Herein, we present a critical overview of the progress on the OFBs, including the design principles of key components (redox-active molecules, membranes, and electrodes) and the latest achievement in both aqueous and nonaqueous systems. Finally, future directions in explorations of the high-performance OFB for electrochemical energy storage are also highlighted.

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DNP NMR reveals the hidden surface C-C bond growth mechanism over ZnAlOx during syngas conversion Pan Gao, Dong Xiao, Zhenchao Zhao, Subhradip Paul, Frédéric Blanc, Xiuwen Han, Guangjin Hou, Xinhe Bao 2022, 67(4): 640-644.  DOI: 10.1016/j.jechem.2021.10.033 Abstract ( 18 )   PDF (1432KB) ( 6 )

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Anti-aggregation growth and hierarchical porous carbon encapsulation enables the C@VO2 cathode with superior storage capability for aqueous zinc-ion batteries Ming Yang, Yanyi Wang, Zhongwei Sun, Hongwei Mi, Shichang Sun, Dingtao Ma, Peixin Zhang 2022, 67(4): 645-654.  DOI: 10.1016/j.jechem.2021.10.025 Abstract ( 10 )   PDF (8892KB) ( 2 )   Self-aggregation and sluggish transport kinetics of cathode materials would usually lead to the poor elec- trochemical performance for aqueous zinc-ion batteries (AZIBs). In this work, we report the construction of C@VO2 composite via anti-aggregation growth and hierarchical porous carbon encapsulation. Both of the morphology of composite and pore structure of carbon layer can be regulated by tuning the adding amount of glucose. When acting as cathode applied for AZIBs, the C@VO2-3:3 composite can deliver a high capacity of 281 mAh g-1 at 0.2 A g-1. Moreover, such cathode also exhibits a remarkably rate capa- bility and cyclic stability, which can release a specific capacity of 195 mAh g-1 at 5 A g-1 with the capacity retention of 95.4% after 1000 cycles. Besides that, the evolution including the crystal structure, valence state and transport kinetics upon cycling were also deeply investigated. In conclusion, benefited from the synergistic effect of anti-aggregation morphology and hierarchical porous carbon encapsulation, the building of such C@VO2 composite can be highly expected to enhance the ion accessible site, boost the transport kinetics and thus performing a superior storage performance. Such design concept can be applied for other kinds of electrode materials and accelerating the development of high- performance AZIBs.

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Insights into the enhanced structure stability and electrochemical performance of Ti4+/F co-doped P2-Na0.67Ni0.33Mn0.67O2 cathodes for sodium ion batteries at high voltage Pengfei Zhou, Jing Zhang, Zhennan Che, Zuhao Quan, Ju Duan, Xiaozhong Wu, Junying Weng, Jinping Zhao, Jin Zhou 2022, 67(4): 655-662.  DOI: 10.1016/j.jechem.2021.10.032 Abstract ( 17 )   PDF (7175KB) ( 13 )   P2-Na0.67Ni0.33Mn0.67O2 is considered as a promising cathode material for sodium-ion battery (SIBs) because of its high capacity and discharge potential. However, its practical use is limited by Na+acancy ordering and P2-O2 phase transition. Herein, a Ti4+/F_ co-doping strategy is developed to address these issues. The optimal P2-Na0.67Ni0.33Mn0.37Ti0.3O1.9F0.1 exhibits much enhanced sodium storage performance in the high voltage range of 2.0-4.4 V, including a cycling stability of 77.2% over 300 cycles at a rate of 2 C and a high-rate capability of 87.7 mAh g_1 at 6 C. Moreover, the P2-Na0.67Ni0.33Mn0.37Ti0.3O1.9F0.1 delivers reversible capacities of 82.7 and 128.1 mAh g_1 at _10 and 50 _C at a rate of 2 C, respectively. The capacity retentions over 200 cycles at _10 _C is 94.2%, implying more opportunity for practical application. In-situ X-ray diffraction analysis reveals that both P2-O2 phase transitions and Na+acancy ordering is suppressed by Ti4+/F_ co-doping, which resulting in fast Na+ diffusion and stable phase structure. The hard carbon//P2-Na0.67Ni0.33Mn0.37Ti0.3O1.9F0.1 full cell exhibits a high energy density of 310.2 Wh kg_1 and remarkable cyclability with 82.1% retention after 300 cycles at 1 C in the voltage range of 1.5-4.2 V. These results demonstrate that the co-doping Ti4+/F_ is a promising strategy to improve the electrochemical properties of P2-Na0.67Ni0.33Mn0.67O2, providing a facile tacticto develop high performance cathode materials for SIBs.

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Rapid determination of lithium-ion battery degradation: High C-rate LAM and calculated limiting LLI Gyuwon Seo, Jaeyun Ha, Moonsu Kim, Jihyeon Park, Jaewon Lee, Eunoak Park, Sungyool Bong, Kiyoung Lee, Soon Jong Kwon, Seung-pil Moon, Jinsub Choi, Jaeyoung Lee 2022, 67(4): 663-671.  DOI: 10.1016/j.jechem.2021.11.009 Abstract ( 23 )   PDF (7216KB) ( 17 )   Herein, incremental capacity-differential voltage (IC-DV) at a high C-rate (HC) is used as a non-invasive diagnostic tool in lithium-ion batteries, which inevitably exhibit capacity fading caused by multiple mechanisms during charge/discharge cycling. Because battery degradation modes are complex, the simple output of capacity fading does not yield any useful data in that respect. Although IC and DV curves obtained under restricted conditions (<; 0.1C, 25 _C) were applied in non-invasive analysis for accurate observation of degradation symptoms, a facile, rapid diagnostic approach without intricate, complex calculations is critical in on-board applications. Herein, LiNi0.5Mn0.3Co0.2O2 (NMC532)/graphite pouch cells were cycled at 4 and 6C and the degradation characteristics, i.e., loss of active materials (LAM) and loss of lithium inventory (LLI), were parameterized using the IC-DV curves. During the incremental current cycling, the initial steep LAM and LLI slopes underwent gradual transitions to gentle states and revealed the gap between low- and high-current measurements. A quantitative comparison of LAM at high and low C-rate showed that a ICHC revealed the relative amount of available reaction region limited by cell polarization. However, this did not provide a direct relationship for estimating the LAM at a low Crate. Conversely, the limiting LLI, which is calculated at a C-rate approaching 0, was obtained by extrapolating the LLI through more than two points measured at high C-rate, and therefore, the LLI at 0.1C was accurately determined using rapid cycling.

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The roles of black phosphorus in performance enhancement of halide perovskite solar cells Damir Aidarkhanov, Charles Surya, Annie Ng 2022, 67(4): 672-683.  DOI: 10.1016/j.jechem.2021.11.006 Abstract ( 8 )   PDF (7059KB) ( 2 )   Hybrid organic-inorganic perovskite solar cells (PSCs) are considered to be the most promising third- generation photovoltaic (PV) technology with the most rapid rate of increase in the power conversion efficiency (PCE). To date, their PCE values are comparable to the established photovoltaic technologies such as crystalline silicon. Intensive research activities associated with PSCs have been being performed, since 2009, aiming to further boost the device performance in terms of efficiency and stability via differ- ent strategies in order to accelerate the progress of commercialization. The emerging 2D black phospho- rus (BP) is a novel class of semiconducting material owing to its unique characteristics, allowing them to become attractive materials for applications in a variety of optical and electronic devices, which have been comprehensively reviewed in the literature. However, comprehensive reviews focusing on the application of BP in PSCs are scarce in the community. This review discusses the research works with the incorporation of BP as a functional material in PSCs. The methodology as well as the effects of employing BP in different regions of PSCs are summarized. Further challenges and potential research directions are also highlighted.

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Mg-based inorganic nanofibers constructing fast and multi-dimensional ion conductive pathways for all-solid-state lithium metal batteries Wen Yu, Nanping Deng, Zirui Yan, Lu Gao, Kewei Cheng, Xiaohui Tian, Lin Tang, Bowen Cheng, Weimin Kang 2022, 67(4): 684-696.  DOI: 10.1016/j.jechem.2021.11.015 Abstract ( 7 )   PDF (11729KB) ( 3 )   Solid-state electrolytes (SSEs), which replace flammable and toxic liquid electrolytes, have attracted widely attention. However, there exist still some challenges in actual application such as poor interfacial compatibility and slow ionic migration. In this study, MgO nanofibers and MgF2 nanofibers were pre- pared via the electro-blow spinning and high-temperature calcination methods, and were applied to all-solid-state lithium metal batteries for the first time. The organic-inorganic composite SSEs exhibited continuous conduction paths based on the virtue of the nanofibers with high length-to-diameter ratio, which were designed and prepared by mixing prepared fillers into the poly(ethylene oxide) (PEO)/ lithium bis(trifluoromethane) sulfonilimide (LiTFSI) system. The effect of filler with different morpholo- gies, doping ratios and component on ionic conductivity, electrochemical stability and cycle performance were explored under two kinds of [EO]/[Li+] ratios and ambient temperatures. The ionic conductivities of electrolytes containing MgO and MgF2 nanofibers can reach up to 1.19 ×; 10 4 and 1.39 ×; 10 4 S cm 1 at 30 C, respectively. They were attributed to specific ionic conductive enhancement at the organic- inorganic interface, reduced crystallinity and Lewis acid interaction, which can effectively promote the dissociation of the lithium salts. Especially MgF2 nanofiber, combining low electronic conductance, excel- lent electrochemical stability and outstanding inhibition for lithium dendrites of fluorides, endowed the battery with an initial specific capacity of 140.6 mAh g 1 and capacity decay rate per cycle of 0.055% after 500 cycles at 50 C. The work can provide an idea to design SSE with fast and multi-dimensional Li con- ductive paths and excellent interfacial compatibility.

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Recent advances on quasi-solid-state electrolytes for supercapacitors Murilo M. Amaral, Raissa Venâncio, Alfredo C. Peterlevitz, Hudson Zanin 2022, 67(4): 697-717.  DOI: 10.1016/j.jechem.2021.11.010 Abstract ( 26 )   PDF (6293KB) ( 19 )   Solid-state and quasi-solid-state electrolytes have been attracting the scientific community’s attention in the last decade. These electrolytes provide significant advantages, such as the absence of leakage and sep- arators for devices and safety for users. They also allow the assembly of stretchable and bendable super- capacitors. Comparing solid-state to quasi-solid-states, the last provides the most significant energy and power densities due to the better ionic conductivity. Our goal here is to present recent advances on quasi- solid-state electrolytes, including gel-polymer electrolytes. We reviewed the most recent literature on quasi-solid-state electrolytes with different solvents for supercapacitors. Organic quasi-solid-state elec- trolytes need greater attention once they reach an excellent working voltage window greater than 2.5 V. Meanwhile, aqueous-based solid-state electrolytes have a restricted voltage window to less than 2 V. On the other hand, they are easier to handle, provide greater ionic conductivity and capacitance. Recent water-in-salt polymer-electrolytes have shown stability as great as 2 V encouraging further development in aqueous-based quasi-solid-state electrolytes. Moreover, hydrophilic conductive polymers have great commercial appeal for bendable devices. Thus, these electrolytes can be employed in flexible and bend- able devices, favoring the improvement of portable electronics and wearable devices (376 references were evaluated and summarized here).

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Electrolyte-dependent formation of solid electrolyte interphase and ion intercalation revealed by in situ surface characterizations Shiwen Li, Chao Wang, Caixia Meng, Yanxiao Ning, Guohui Zhang, Qiang Fu 2022, 67(4): 718-726.  DOI: 10.1016/j.jechem.2021.10.003 Abstract ( 9 )   PDF (11047KB) ( 4 )   The formation of solid electrolyte interphase (SEI) and ion intercalation are two key processes in rechargeable batteries, which need to be explored under dynamic operating conditions. In this work, both planar and sandwich model lithium batteries consisting of Li metal | ionic liquid electrolyte | graphite electrode have been constructed and investigated by a series of in situ surface analysis platforms includ- ing atomic force microscopy, Raman and X-ray photoelectron spectroscopy. It is found that the choice of electrolyte, including the concentration and contents, has a profound effect on the SEI formation and evo- lution, and the subsequent ion intercalation. A smooth and compact SEI is preferably produced in high- concentration electrolytes, with FSI salt superior to TFSI salt, facilitating the lithiation/delithiation to achieve high capacity and excellent cycle stability, while suppressing the co-intercalation of electrolyte solvent ions. The innovative research scenario of well-defined model batteries in combination with mul- tiple genuinely in situ surface analysis methods presented herein leads to insightful results, which pro- vide valuable strategies for the rational design and optimization of practical batteries, and energy storage devices in general.

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Interfacial nitrogen engineering of robust silicon/MXene anode toward high energy solid-state lithium-ion batteries Xiang Han, Weijun Zhou, Minfeng Chen, Jizhang Chen, Guanwen Wang, Bo Liu, Linshan Luo, Songyan Chen, Qiaobao Zhang, Siqi Shi, Ching-Ping Wong 2022, 67(4): 727-735.  DOI: 10.1016/j.jechem.2021.11.021 Abstract ( 13 )   PDF (11458KB) ( 7 )   Replacing the conventional carbonate electrolyte by solid-state electrolyte (SSE) will offer improved safety for lithium-ion batteries. To further improve the energy density, Silicon (Si) is attractive for next generation solid-state battery (SSB) because of its high specific capacity and low cost. High energy den- sity and safe Si-based SSB, however, is plagued by large volume change that leads to poor mechanical sta- bility and slow lithium ions transportation at the multiple interfaces between Si and SSE. Herein, we designed a self-integrated and monolithic Si/two dimensional layered T3C2Tx (MXene, Tx stands for terminal functional groups) electrode architecture with interfacial nitrogen engineering. During a heat treatment process, the polyacrylonitrile not only converts into amorphous carbon (a-C) that shells Si but also forms robust interfacial nitrogen chemical bonds that anchors Si and MXene. During repeated lithiation and delithiation processes, the robust interfacial engineered Si/MXene configuration enhances the mechanical adhesion between Si and MXene that improves the structure stability but also contributes to form stable solid-electrolyte interphase (SEI). In addition, the N-MXene provides fast lithium ions transportation pathways. Consequently, the Si/MXene with interfacial nitrogen engineering (denoted as Si-N-MXene) deliveres high-rate performance with a specific capacity of 1498 mAh g-1 at a high current of 6.4 A g-1. A Si-N-MXene/NMC full cell exhibited a capacity retention of 80.5% after 200 cycles. The Si-N-MXene electrode is also applied to SSB and shows a relative stable cycling over 100 cycles, demonstrating the versatility of this concept.

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Cellulose nanofiber separator for suppressing shuttle effect and Li dendrite formation in lithium-sulfur batteries Jingxue Li, Liqin Dai, Zhefan Wang, Hao Wang, Lijing Xie, Jingpeng Chen, Chong Yan, Hong Yuan, Hongliang Wang, Chengmeng Chen 2022, 67(4): 736-744.  DOI: 10.1016/j.jechem.2021.11.017 Abstract ( 27 )   PDF (9786KB) ( 25 )   Lithium-sulfur battery (LSB) has high energy density but is limited by the polysulfides shuttle and den- drite growth during cycling. Herein, a free-standing cellulose nanofiber (CNF) separator is designed and fabricated in isopropanol/water suspension through vacuum filtration progress. CNFs with abundant polar oxygen-containing functional groups can chemically immobilize the polysulfides, and suppress the formation of the dendrites by controlling the surface morphology of the SEI on lithium metal in LSB. The isopropanol content in a suspension can fine-tune the pore structure of the membrane to achieve optimal electrochemical performance. The prepared separator displays integrated advantages of an ultra-thin thickness (19 lm), lightweight (0.87 mg cm 2), extremely high porosity (98.05%), and decent elec-trolyte affinity. As a result, the discharge capacity of the LSB with CNF separator at the first and 100th cycle is 1.4 and 1.3 times that of PP separator, respectively. Our research provides an environmental- friendly and facile strategy for the preparation of multifunctional separators for LSBs.

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Black phosphorus-based heterostructures for photocatalysis and photoelectrochemical water splitting Shutao Li, Yihe Zhang, Hongwei Huang 2022, 67(4): 745-779.  DOI: 10.1016/j.jechem.2021.11.023 Abstract ( 14 )   PDF (32170KB) ( 22 )   Semiconductor-based photocatalytic and photoelectrochemical (PEC) processes can convert solar energy into high-density chemical energy or for the treatment of environmental pollutants, which are ideal ways to deal with environmental and energy crises. The development of high-efficiency photocatalysts and photoelectrodes is the key to the in-depth development and practical application of the two technologies. Black phosphorus (BP) has excellent physicalcochemical properties such as adjustable band gap, high carrier mobility, large specific surface area and anisotropy, making it one of the most promising catalysts. BP-based heterostructure can not only realize the effective separation of photogenerated carriers but also improve the stability of BP, and is widely used in photocatalytic and PEC reactions. In this review, we first introduce the crystal structure, band structure, anisotropy, and preparation of BP with different dimensions (bulk, zero-dimension and two-dimension). Then, according to the transfer path of the pho- togenerated carriers and the components, the BP-based heterostructures are divided into type I heterojunction, type II heterojunction, Z-scheme heterojunction, S-scheme heterojunction, BP/carbon- based material heterostructure, BP/metal heterostructure and multi-component heterostructure. Highlighted are the diverse photocatalytic applications of BP-based heterostructure, such as water splitting and CO2 reduction, N2 fixation, pollutant degradation, photothermal and photodynamic therapy. Finally, some concluding views and opinions are stated on the challenges and opportunities faced by the further development of BP-based heterostructures in photocatalysis and PEC water splitting.

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Insights into the nitride-regulated processes at the electrolyte/electrode interface in quasi-solid-state lithium metal batteries Jing Wan, Wan-Ping Chen, Gui-Xian Liu, Yang Shi, Sen Xin, Yu-Guo Guo, Rui Wen, Li-Jun Wan 2022, 67(4): 780-786.  DOI: 10.1016/j.jechem.2021.10.021 Abstract ( 6 )   PDF (3844KB) ( 9 )   Gel polymer electrolytes (GPEs) are one of the promising candidates for high-energy-density quasi-solid-state lithium metal batteries (QSSLMBs), for their high ionic conductivity and excellent interfacial compatibility. The comprehension of dynamic evolution and structure-reactivity correlation at the GPE/Li interface becomes significant. Here, in situ electrochemical atomic force microscopy (EC-AFM) provides insights into the LiNO3-regulated micromechanism of the Li plating/stripping pro- cesses upon cycles in GPE-based LMBs at nanoscale. The additive LiNO3 induces the formation of amor- phous nitride SEI film and facilitates Li+ ion diffusion. It stabilizes a compatible interface and regulates the Li nucleation/growth at steady kinetics. The deposited Li is in the shape of chunks and tightly compact. The Li dissolution shows favorable reversibility, which guarantees the cycling performance of LMBs. In situ AFM monitoring provides a deep understanding into the dynamic evolution of Li deposition/dissolu- tion and the interphasial properties of tunable SEI film, regulating the rational design of electrolyte and optimizing interfacial establishment for GPE-based QSSLMBs.

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Bismuth nanorods confined in hollow carbon structures for high performance sodium- and potassium-ion batteries Hongli Long, Xiuping Yin, Xuan Wang, Yufeng Zhao, Liuming Yan 2022, 67(4): 787-796.  DOI: 10.1016/j.jechem.2021.11.011 Abstract ( 14 )   PDF (11447KB) ( 11 )   Bismuth has drawn widespread attention as a prospective alloying-type anode for sodium-ion batteries (SIBs) and potassium-ion batteries (PIBs) due to its large volumetric capacity. However, such material encounters drastic particle pulverization and overgrowth of solid-electrolyte interphase (SEI) upon repeated (de)alloying, thus causing poor rate and cycling degradation. Herein, we report a unique struc- ture design with bismuth nanorods confined in hollow N, S-codoped carbon nanotubes (Bi@NS-C) fabri- cated by a solvothermal method and in-situ thermal reduction. Ex-situ SEM observations confirm that such a design can significantly suppress the size fining of Bi nanorods, thus inhibiting the particle pulver- ization and repeated SEI growth upon charging/discharging. The as achieved Bi@NS-C demonstrates out- standing rate capability for SIBs (96.5% capacity retention at 30 A g 1 vs. 1 A g 1), and a record high rate performance for PIBs (399.5 mAh g 1 @20 A g 1). Notably, the as constructed full cell (Na3V2(PO4)3@C| Bi@NS-C) demonstrates impressive performance with a high energy density of 219.8 W h kg 1 and a high-power density of 6443.3 W kg 1 (based on the total mass of active materials on both electrodes), outperforming the state-of-the-art literature.

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D-p-D molecular layer electronically bridges the NiOx hole transport layer and the perovskite layer towards high performance photovoltaics Rongguo Xu, Xiuwen Xu, Ruixi Luo, Yu Li, Gaopeng Wang, Tongfa Liu, Ning Cai, Shihe Yang 2022, 67(4): 797-804.  DOI: 10.1016/j.jechem.2021.11.029 Abstract ( 7 )   PDF (4457KB) ( 4 )   Nickel oxide (NiOx) has significant cost and stability advantages over poly[bis (4-phenyl)(2,4,6-trimethyl phenyl)amine] (PTAA) for inverted p-i-n perovskite solar cells (PSCs), but the poor NiOx/perovskite contact stemming from some reactive species at the interface led to suboptimal device performance. To solve this problem, we take amultiple donor molecule approach, using 3,30-(4,8-bis(hexylthio)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl)bis(10-(6-bromohexyl)-10H-phenoxazine) (BDT-POZ) as an example, to modify the NiOx/perovskite interface. The primary goal was to reduce the under-coordinated Ni 3+ cations via electron transfer from the donor molecules to NiOx, thus mitigating the detrimental reactions between perovskite and NiOx. Equally importantly, the hole extraction at the interface was greatly enhanced after the organic donor modification, since the hydrophobic species atop NiOx not only enabled pinhole-free crystallization of the perovskite but also properly tuned the interfacial energy level alignment. Consequently, the PSCs with NiOx/BDT-POZ HTL achieved a high power conversion efficiency (PCE) up to 20.16%, which compared excellently with that of the non-modified devices (17.83%). This work provides a new strategy to tackle the exacting issues that have so far impeded the development of NiOx based PSCs.

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Unveiling the promotion of accelerated water dissociation kinetics on the hydrogen evolution catalysis of NiMoO4 nanorods Tuzhi Xiong, Bowen Huang, Jingjing Wei, Xincheng Yao, Ran Xiao, Zhixiao Zhu, Fang Yang, Yongchao Huang, Hao Yang, M.-SadeeqBalogun 2022, 67(4): 805-813.  DOI: 10.1016/j.jechem.2021.11.025 Abstract ( 7 )   PDF (9154KB) ( 4 )   Nickel molybdate (NiMoO4) attracts superior hydrogen desorption behavior but noticeably poor for effi- ciently driving the hydrogen evolution reaction (HER) in alkaline media due to the sluggish water disso- ciation step. Herein, we successfully accelerate the water dissociation kinetics of NiMoO4 for prominent HER catalytic properties via simultaneous in situ interfacial engineering with molybdenum dioxide (MoO2) and doping with phosphorus (P). The as-synthesized P-doped NiMoO4/MoO2 heterostructure nanorods exhibit outstanding HER performance with an extraordinary low overpotential of 23 mV at a current density of 10 mA cm 2, which is highly comparable to the performance of the state-of-art Pt/C coated on nickel foam (NF) catalyst. The density functional theory (DFT) analysis reveals the enhanced performance is attributed to the formation of MoO2 during the in situ epitaxial growth that sub- stantially reduces the energy barrier of the Volmer pathway, and the introduction of P that provides effi- cient hydrogen desorption of NiMoO4. This present work creates valuable insight into the utilization of interfacial and doping systems for hydrogen evolution catalysis and beyond.

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High-performance solid-solution potassium-ion intercalation mechanism of multilayered turbostratic graphene nanosheets Jiae Um, Seung Uk Yoon, Hoseong Kim, Beom Sik Youn, Hyoung-Joon Jin, Hyung-Kyu Lim, Young Soo Yun 2022, 67(4): 814-823.  DOI: 10.1016/j.jechem.2021.11.027 Abstract ( 7 )   PDF (6966KB) ( 2 )   The solid-solution reaction between an alkali cation and an active host material is known as a singlephase redox mechanism, and it is typically accompanied by a continuous voltage change. It is distinct from the typical alkali cation intercalation reaction at an equivalent site of the active host material, which exhibits a voltage plateau. Herein, we report an unusual solid-solution potassium-ion intercalation mechanism with a low-voltage plateau capacity on multilayered turbostratic graphene nanosheets (T-GNSs). Despite the disordered graphitic structure with a broad range of d-spacings (3.65-4.18 Å), the T-GNSs showed a reversible plateau capacity of _ 200 mA h g_1, which is higher than that of a well-ordered graphite nanoplate (_120 mA h g_1). In addition, a sloping capacity of _ 220 mA h g_1 was delivered with the plateau capacity, and higher rate capabilities, better reversibility, and a more stable cycling performance were confirmed on the turbostratic microstructure. First-principles calculations suggest that the multitudinous lattice domains of the T-GNSs contain diverse intercalation sites with strong binding energies, which could be the origin of the high-performance solid-solution potassium-ion intercalation behavior when the turbostratic graphene stacks have a d-spacing smaller than that of equilibrium potassium-graphite intercalation compounds (5.35 Å).

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Surface Brønsted-Lewis dual acid sites for high-efficiency dinitrogen photofixation in pure water Cai Chen, Jiewei Chen, Zhiyuan Wang, Fei Huang, Jian Yang, Yunteng Qu, Kuang Liang, Xiao Ge, Yanggang Wang, Hui Zhang, Yuen Wu 2022, 67(4): 824-830.  DOI: 10.1016/j.jechem.2021.10.039 Abstract ( 15 )   PDF (4257KB) ( 9 )