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2022, Vol. 65, No. 2　Online: 15 February 2022

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Inhibiting manganese (II) from catalyzing electrolyte decomposition in lithium-ion batteries Xuehuan Luo, Lidan Xing, Jenel Vatamanu, Jiawei Chen, Jiakun Chen, Mingzhu Liu, Cun Wang, Kang Xu, Weishan Li 2022, 65(2): 1-8.  DOI: 10.1016/j.jechem.2021.05.022 Abstract ( 17 )   PDF (3775KB) ( 6 )   A once overlooked source of electrolyte degradation incurred by dissolved manganese (II) species in lithium-ion batteries has been identified recently. In order to deactivate the catalytic activity of such manganese (II) ion, 1-aza-12-crown-4-ether (A12C4) with cavity size well matched manganese (II) ion is used in this work as electrolyte additive. Theoretical and experimental results show that stable complex forms between A12C4 and manganese (II) ions in the electrolyte, which does not affect the solvation of Li ions. The strong binding effect of A12C4 additive reduces the charge density of manganese (II) ion and inhibits its destruction of the PF6- structure in the electrolyte, leading to greatly improved thermal stability of manganese (II) ions-containing electrolyte. In addition to bulk electrolyte, A12C4 additive also shows capability in preventing Mn2+ from degrading SEI on graphite surface. Such bulk and interphasial stability introduced by A12C4 leads to significantly improved cycling performance of LIBs.

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Thermotolerant and fireproof gel polymer electrolyte toward high-performance and safe lithium-ion battery Man-Cheng Long, Ting Wang, Ping-Hui Duan, You Gao, Xiu-Li Wang, Gang Wu, Yu-Zhong Wang 2022, 65(2): 9-18.  DOI: 10.1016/j.jechem.2021.05.027 Abstract ( 21 )   PDF (10863KB) ( 3 )   Poly(ethylene oxide) (PEO) and its derivatives based gel polymer electrolytes (GPEs) are severely limited in advanced and safe lithium-ion batteries (LIBs) owing to the intrinsically high flammability of liquid electrolytes and PEO. Directly adding flame retardants to the GPEs can suppress their flammability and thus improve the safety of LIBs, but results in deteriorative electrochemical performance. Herein, a novel GPE with chemically bonded flame retardant (i.e. diethyl vinylphosphonate) in cross-linked polyethylene glycol diacrylate matrix, featuring both high-safety and high-performance, is designed. This as-prepared GPE storing the commercial 1 mol L-1 LiPF6 electrolyte resists high temperature of 200 °C and cannot be ignited as well as possesses a high ionic conductivity (0.60 mS cm-1) and good compatibility with lithium. Notably, the LiFePO4/Li battery with this GPE delivers a satisfactory capacity of 142.2 mA h g-1 and a superior cycling performance with a capacity retention of 96.3% and a coulombic efficiency of close to 100% for 350 cycles at 0.2 C under ambient temperature. Furthermore, the battery can achieve steady charge-discharge for 100 cycles with a coulombic efficiency of 99.5% at 1 C under 80 °C and run normally even at a high temperature of 150 °C or under the exposure to butane flame. Differential scanning calorimetry manifests significantly improved battery safety compared to commercial battery systems. This work provides a new pathway for developing next-generation advanced LIBs with enhanced performance and high safety.

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Formation of multifaceted nano-groove structure on rutile TiO2 photoanode for efficient electron-hole separation and water splitting Xiaoyi Zhan, Yaling Luo, Ziyu Wang, Yao Xiang, Zheng Peng, Yong Han, Hui Zhang, Ruotian Chen, Qin Zhou, Hongru Peng, Hao Huang, Weimin Liu, Xin Ou, Guijun Ma, Fengtao Fan, Fan Yang, Can Li, Zhi Liu 2022, 65(2): 19-25.  DOI: 10.1016/j.jechem.2021.05.007 Abstract ( 27 )   PDF (5981KB) ( 2 )   Photoelectrochemical (PEC) water-splitting using solar energy holds great promise for the renewable energy future, and a key challenge in the development of industry viable PEC devices is the unavailability of high-efficient photoanodes. Herein, we designed a TiO2 model photocatalyst with nano-groove pattern and different surface orientation using low-energy Ar+ irradiation and photoetching of TiO2, and significantly improved the intrinsic activity for PEC water oxidation. High-resolution transmission electron microscopy directly manifests that the grooves consist of highly stepped surface with < 110 > steps and well-crystallized. Transient absorption spectroscopy reveals the groove surface that allows for increased recovery lifetime, which ensures promoted electron-hole separation efficiency. Surface photovoltage directly shows the carrier separation and transportation behaviors, verified by selective photodeposition, demonstrating the groove surface on TiO2 contributes to electron-hole separation. This work proposes an efficient and scalable photoanode strategy, which potentially can open new opportunities for achieving efficient PEC water oxidation performance.

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3D MoS2 foam integrated with carbon paper as binder-free anode for high performance sodium-ion batteries Fangying Zheng, Zeyu Wei, Huicong Xia, Yunchuan Tu, Xiangyu Meng, Kaixin Zhu, Jiao Zhao, Yimin Zhu, Jianan Zhang, Yan Yang, Dehui Deng 2022, 65(2): 26-33.  DOI: 10.1016/j.jechem.2021.05.021 Abstract ( 8 )   PDF (5262KB) ( 4 )   Molybdenum sulfide (MoS2) with well-designed porous structure has the potential to be great electrode materials in sodium-ion batteries due to its high theoretical capacity and abundant resource, however, hindered by its intrinsic low conductivity and stability. Herein, MoS2 with 3D macroporous foam structure and high conductivity was obtained through SiO2 templates and integrated with carbon paper (3D F-MoS2/CP). It has showed superior specific capacity (225 mA h g-1, 0.4-3 V) and cycling stability (1000 cycles) at high rate (2000 mA g-1), with a low decay rate (0.033% per cycle) in sodium-ion batteries. The excellent electrochemical performance may originate from its unique integrated structure: 3D MoS2 macropores providing high surface area and abundant transfer channels while carbon paper enhancing the conductivity of MoS2 and avoiding unnecessary side reactions brought by binder addition.

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Confined Ni-In intermetallic alloy nanocatalyst with excellent coking resistance for methane dry reforming Wenming Liu, Le Li, Sixue Lin, Yiwei Luo, Zhenghong Bao, Yiru Mao, Kongzhai Li, Daishe Wu, Honggen Peng 2022, 65(2): 34-47.  DOI: 10.1016/j.jechem.2021.05.017 Abstract ( 10 )   PDF (15996KB) ( 2 )   Carbon dioxide and methane are two main greenhouse gases which are contributed to serious global warming. Fortunately, dry reforming of methane (DRM), a very important reaction developed decades ago, can convert these two major greenhouse gases into value-added syngas or hydrogen. The main problem retarding its industrialization is the seriously coking formation upon the nickel-based catalysts. Herein, a series of confined indium-nickel (In-Ni) intermetallic alloy nanocatalysts (InxNi@SiO2) have been prepared and displayed superior coking resistance for DRM reaction. The sample containing 0.5 wt.% of In loading (In0.5Ni@SiO2) shows the best balance of carbon deposition resistance and DRM reactivity even after 430 h long term stability test. The boosted carbon resistance can be ascribed to the confinement of core-shell structure and to the transfer of electrons from Indium to Nickel in In-Ni intermetallic alloys due to the smaller electronegativity of In. Both the silica shell and the increase of electron cloud density on metallic Ni can weaken the ability of Ni to activate C-H bond and decrease the deep cracking process of methane. The reaction over the confined InNi intermetallic alloy nanocatalyst was conformed to the Langmuir-Hinshelwood (L-H) mechanism revealed by in situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS). This work provides a guidance to design high performance coking resistance catalysts for methane dry reforming to efficiently utilize these two main greenhouse gases.

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Ultra-small platinum nanoparticles segregated by nickle sites for efficient ORR and HER processes Lvhan Liang, Huihui jin, Huang Zhou, Bingshuai Liu, Chenxi Hu, Ding Chen, Jiawei Zhu, Zhe Wang, Hai-Wen Li, Suli Liu, Daping He, Shichun Mu 2022, 65(2): 48-54.  DOI: 10.1016/j.jechem.2021.05.033 Abstract ( 6 )   PDF (10573KB) ( 1 )   In the electrochemical process, Pt nanoparticles (NPs) in Pt-based catalysts usually agglomerate due to Oswald ripening or lack of restraint, ultimately resulting in reduction of the active sites and catalytic efficiency. How to uniformly disperse and firmly fix Pt NPs on carbon matrix with suitable particle size for catalysis is still a big challenge. Herein, to prevent the agglomeration and shedding of Pt NPs, Ni species is introduced and are evenly dispersed in the surface of carbon matrix in the form of Ni-N-C active sites (Ni ZIF-NC). The Ni sites can be used to anchor Pt NPs, and then effectively limit the further growth and agglomeration of Pt NPs during the reaction process. Compared with commercial Pt/C catalyst, Pt@Ni ZIF-NC, with ultralow Pt loading (7 wt%) and ideal particle size (2.3 nm), not only increases the active center, but also promotes the catalysis kinetics, greatly improving the ORR and HER catalytic activity. Under acidic conditions, its half-wave potential (0.902 V) is superior to commercial Pt/C (0.861 V), and the mass activity (0.38 A per mg Pt) at 0.9 V is 4.7 times that of Pt/C (0.08 A per mg Pt). Besides, it also shows outstanding HER performance. At 20 and 30 mV, its mass activity is even 2 and 6 times that of Pt/C, respectively. Whether it is under ORR or HER conditions, it still shows excellent durability. These undoubtedly indicate the realization of dual-functional catalysts with low-Pt and high-efficiency properties.

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Enlarging grain sizes for efficient perovskite solar cells by methylamine chloride assisted recrystallization Gao Wu, Molang Cai, Yujia Cao, Zhuoxin Li, Zhongyan Zhang, Weng Yang, Xianggang Chen, Dongxu Ren, Yaqi Mo, Miao Yang, Xuepeng Liu, Songyuan Dai 2022, 65(2): 55-61.  DOI: 10.1016/j.jechem.2021.05.026 Abstract ( 7 )   PDF (4794KB) ( 2 )   The quality of MAPbI3 film prepared by solvent engineering process highly depends on environment and antisolvent control. Here, we provided a simple methylamine chloride (MACl) solution treatment using a two-step process to enlarge the perovskite crystal grain sizes to more than 1 μm. Other than treatment on the film surface, the MACl solution diffuses into the MAPbI3 films to assist the recrystallization of small crystal at the bottom of perovskite film. The imitative contact between perovskite and substrate is formed. Meanwhile, the enlargement of grain size and ten times enhancement of crystalline reduce trap-assisted recombination of perovskite films. Thus, the significant improvement of cell efficiency of 20.89% as well as device stability is obtained with the MACl treatment.

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Tuning the phase evolution pathway of LiNi0.5Mn1.5O4 synthesis from binary intermediates to ternary intermediates with thermal regulating agent Libin Wu, Hua Huo, Qun Wang, Xucai Yin, Shu Guo, Jiajun Wang, Chunyu Du, Pengjian Zuo, Geping Yin, Yunzhi Gao 2022, 65(2): 62-70.  DOI: 10.1016/j.jechem.2021.05.031 Abstract ( 6 )   PDF (5397KB) ( 3 )   Transition metal cation ordering is essential for controlling the electrochemical performance of cubic spinel LiNi0.5Mn1.5O4 (LNMO), which is conventionally adjusted by optimizing the high temperature sintering and annealing procedures. In this present work, multiple characterization techniques, including 6,7Li NMR, XRD and HRTEM, have been combined to trace the phase transformation and morphology evolution during synthesis. It has been illustrated that simultaneous formation of LiMn2O4 (LMO) and LiNiO2 (LNO) binary oxides and their conversion into highly reactive LixNi3+yMn3.5+zO ternary intermediate is a thermal dynamically difficult but crucial step in the synthesis of LNMO ternary oxide. A new strategy of modifying the intermediates formation pathway from binary mode to ternary mode using thermal regulating agent has been adopted. LNMO synthesized with thermal regulating agent exhibits supreme rate capability, long-cycling performance (even at elevated temperature) and excellent capacity efficiency. At a high rate of 100 C, the assembled battery delivers a discharge capacity of 99 mAh g-1. This study provides a way to control the formation pathway of complex oxides using thermal regulating agent.

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Tuning the reversible chemisorption of hydroxyl ions to promote the electrocatalysis on ultrathin metal-organic framework nanosheets Hong Yu, Yao Jing, Cheng-Feng Du, Jiong Wang 2022, 65(2): 71-77.  DOI: 10.1016/j.jechem.2021.05.029 Abstract ( 11 )   PDF (6714KB) ( 7 )   Interfacial engineering to alter the configuration of active sites in heterogeneous catalysts is a potential strategy for activity enhancement, but it remains unelucidated for metal-organic frameworks (MOFs). Here, we demonstrate that the surface of two-dimensional Co-based MOF is modified by decorating Ag quantum dots (QDs) simply through in-situ reduction of Ag+ ions. Toward oxygen evolution reaction (OER), it reveals that the catalysis is mediated by the reversible redox of Co sites between Co3+ and Co4+ states coupling with transfer of OH- ions. The decoration of Ag QDs decreases the redox potential of Co sites, and thus effectively decreases the overpotential of OER. The TOFs of Co sites are increased by 77 times to reach 5.4 s-1 at an overpotential of 0.35 V. We attribute the activity enhancement to the tuning of the coupling process between Co sites and OH- ions during the redox of Co sites by Ag QDs decoration based on Pourbaix analysis.

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Electronic structure modulation with ultrafine Fe3O4 nanoparticles on 2D Ni-based metal-organic framework layers for enhanced oxygen evolution reaction Wei Huang, Chao Peng, Jing Tang, Fangyuan Diao, Murat Nulati Yesibolati, Hongyu Sun, Christian Engelbrekt, Jingdong Zhang, Xinxin Xiao, Kristian S. Mølhave 2022, 65(2): 78-88.  DOI: 10.1016/j.jechem.2021.05.030 Abstract ( 10 )   PDF (9389KB) ( 5 )   Two-dimensional (2D) metal organic frameworks (MOFs) are emerging as low-cost oxygen evolution reaction (OER) electrocatalysts, however, suffering aggregation and poor operation stability. Herein, ultrafine Fe3O4 nanoparticles (diameter: 6 ± 2 nm) are homogeneously immobilized on 2D Ni based MOFs (Ni-BDC, thickness: 5 ± 1 nm) to improve the OER stability. Electronic structure modulation for enhanced catalytic activity is studied via adjusting the amount of Fe3O4 nanoparticles on Ni-BDC. The optimal Fe3O4/Ni-BDC achieves the best OER performance with an overpotential of 295 mV at 10 mA cm-2, a Tafel slope of 47.8 mV dec-1 and a considerable catalytic durability of more than 40 h (less than 5 h for Ni-BDC alone). DFT calculations confirm that the active sites for Fe3O4/Ni-BDC are mainly contributed by Fe species with a higher oxidation state, and the potential-determining step (PDS) is the formation of the adsorbed O* species, which are facilitated in the composite.

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A low-cost bromine-fixed additive enables a high capacity retention zinc-bromine batteries Pengcheng Xu, Tianyu Li, Qiong Zheng, Huamin Zhang, Yanbin Yin, Xianfeng Li 2022, 65(2): 89-93.  DOI: 10.1016/j.jechem.2021.05.036 Abstract ( 14 )   PDF (2289KB) ( 12 )

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Au core-PtAu alloy shell nanowires for formic acid electrolysis Qi Xue, Xin-Yu Bai, Yue Zhao, Ya-Nan Li, Tian-Jiao Wang, Hui-Ying Sun, Fu-Min Li, Pei Chen, Pujun Jin, Shi-Bin Yin, Yu Chen 2022, 65(2): 94-102.  DOI: 10.1016/j.jechem.2021.05.034 Abstract ( 15 )   PDF (7758KB) ( 4 )   Inefficient electrocatalysts and high-power consumption are two thorny problems for electrochemical hydrogen (H2) production from acidic water electrolysis. Herein we report the one-pot precise synthesis of ultrafine Au core-PtAu alloy shell nanowires (Au@PtxAu UFNWs). Among them, Au@Pt0.077Au UFNWs exhibit the best performance for formic acid oxidation reaction (FAOR) and hydrogen evolution reaction (HER), which only require applied potentials of 0.29 V and -22.6 mV to achieve a current density of 10 mA cm-2, respectively. The corresponding formic acid electrolyzer realizes the electrochemical H2 production at a voltage of only 0.51 V with 10 mA cm-2 current density. Density functional theory (DFT) calculations reveal that the Au-riched PtAu alloy structure can facilitates the direct oxidation pathway of FAOR and consequently elevates the FAOR activity of Au@Pt0.077Au UFNWs. This work provides meaningful insights into the electrochemical H2 production from both the construction of advanced bifunctional electrocatalysts and the replacement of OER.

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Atom-level interfacial synergy of single-atom site catalysts for electrocatalysis Yao Wang, Dingsheng Wang, Yadong Li 2022, 65(2): 103-115.  DOI: 10.1016/j.jechem.2021.05.038 Abstract ( 6 )   PDF (8982KB) ( 2 )   Single-atom site catalysts (SACs) have made great achievements due to their nearly 100% atomic utilization and uniform active sites. Regulating the surrounding environment of active sites, including electron structure and coordination environment via atom-level interface regulation, to design and construct an advanced SACs is of great significance for boosting electrocatalytic reactions. In this review, we systemically summarized the fundamental understandings and intrinsic mechanisms of SACs for electrocatalytic applications based on the interface site regulations. We elaborated the several different regulation strategies of SACs to demonstrate their ascendancy in electrocatalytic applications. Firstly, the interfacial electronic interaction was presented to reveal the electron transfer behavior of active sites. Secondly, the different coordination structures of metal active center coordinated with two or three non-metal elements were also summarized. In addition, other atom-level interfaces of SACs, including metal atom-atom interface, metal atom-X-atom interface (X: non-metal element), metal atom-particle interface, were highlighted and the corresponding promoting effect towards electrocatalysis was disclosed. Finally, we outlooked the limitations, perspectives and challenges of SACs based on atomic interface regulation.

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One-pot hydrothermal preparation of hierarchical manganese oxide nanorods for high-performance symmetric supercapacitors Bidhan Pandit, Emad S. Goda, Mahmoud H. Abu Elella, Aafaq ur Rehman, Sang Eun Hong, Sachin R. Rondiya, Pranay Barkataki, Shoyebmohamad F. Shaikh, Abdullah M. Al-Enizi, Salah M. El-Bahy, Kuk Ro Yoon 2022, 65(2): 116-126.  DOI: 10.1016/j.jechem.2021.05.028 Abstract ( 6 )   PDF (5915KB) ( 2 )   An eco-friendly, new, and controllable approach for the preparation of manganese oxide (α-MnO2) nanorods has been introduced using hydrothermal reaction for supercapacitor application. The in-depth crystal structure analysis of α-MnO2 is analyzed by X-ray Rietveld refinement by using FullProf program with the help of pseudo-Voigt profile function. The developed α-MnO2 electrode attains a remarkable capacitance of 577.7 F/g recorded at a current density value of 1 A/g with an excellent cycle life when is used for 10,000 repeated cycles due to the porous nanorod-morphology assisting the ease penetration of electrolyte ions into the electroactive sites. The diffusive and capacitive contributions of the electrode have been estimated by considering standard numerical packages in Python. After successfully assembling the aqueous symmetric supercapacitor (SSC) cell by utilizing the as-prepared α-MnO2, an excellent capacitance of 163.5 F/g and energy density of 58.1 Wh/kg at the constant current density of 0.5 A/g are obtained with an expanded potential frame of 1.6 V. Moreover, the cell has exceptionally withstood up to 10,000 cycles with an ultimate capacitance retention of 94.1% including the ability to light an LED for 18 s. Such findings recommend the developed α-MnO2 electrode to be a highly felicitous electrode for the field of energy storage.

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Tailored amorphous titanium oxide and carbon composites for enhanced pseudocapacitive sodium storage Meng Shao, Chengcheng Sun, Tianming Chen, Ningxiang Wu, Runan Zhang, Xu Han, Yu Shen, Peng Wu, Wei-Wei Xiong, Weina Zhang, Sheng Li, Fengwei Huo 2022, 65(2): 127-132.  DOI: 10.1016/j.jechem.2021.05.037 Abstract ( 23 )   PDF (4352KB) ( 15 )

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Realizing high-performance organic solar cells through precise control of HOMO driving force based on ternary alloy strategy Ji Wan, Zeng Chen, Li Zeng, Xunfan Liao, Qiannan He, Siqi Liu, Peipei Zhu, Haiming Zhu, Yiwang Chen 2022, 65(2): 133-140.  DOI: 10.1016/j.jechem.2021.05.053 Abstract ( 10 )   PDF (4481KB) ( 3 )   A good deal of studies have proven that effective exciton dissociation and fast hole transport can operate efficiently in non-fullerene organic photovoltaics (OPVs) despite nearly zero driving force. Even so, whether such a phenomenon is universal and how small the driving force can realize the best photovoltaic performance still require a thorough understanding. Herein, despite the zero driving force based on PM6:F8IC system, a maximum short-circuit current (Jsc) of 23.0 mA/cm2 and high power conversion efficiency (PCE) of 12.2% can still be achieved. Due to the continuously adjustable energy levels can be realized in organic semiconducting alloys including F8IC:IT-4F and F8IC: Y6, the suitable third components can play the role of energy level regulator. Therefore, the HOMO energy level offset (ΔEHOMO(D-A)) from zero to 0.07 and 0.06 eV is accomplished in the optimized IT-4F and Y6 ternary devices. Consequently, both ternary devices achieved substantially increased PCE of 13.8% and Jsc of 24.4 and 25.2 mA/cm2, respectively. Besides, pseudo-planar heterojunction (PPHJ) devices based on alloyed acceptors through sequential spin-coating method further improve the photovoltaic performance. Our work puts forward the concept of energy level regulator and prove that the ternary alloy strategy has unique advantages and huge research potential in continuously adjusting the driving force.

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Molecule functionalization to facilitate electrocatalytic oxygen reduction on graphdiyne Huiying Yao, Yasong Zhao, Nailiang Yang, Wei Hao, Hu Zhao, Shuzhou Li, Jia Zhu, Lin Shen, Weihai Fang 2022, 65(2): 141-148.  DOI: 10.1016/j.jechem.2021.04.052 Abstract ( 9 )   PDF (3368KB) ( 2 )   Chemical doping is verified to be a promising strategy to regulate local electron distribution and further promote the poor intrinsic catalytic activity of graphdiyne. However, the current doping approach still faces problems such as precise doping for creating active sites and the destruction of graphdiyne skeleton calling for high temperature. Here, we achieved charge redistribution on graphdiyne surface through molecule functionalization. A p-type molecule-F4TCNQ (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane) was introduced and the site-defined functionalization was accomplished. Theoretical calculations showed that the charge transfer ability is improved and graphdiyne becomes positively charged. The oxygen reduction electrocatalysis was conducted as a proof of principle, where the electronic states of sp hybridized C active site was tuned toward favorable reaction intermediates’ adsorption. Such work from both theoretical prediction and experimental validation, found that molecule functionalization is effective to promote the electrocatalytic oxygen reduction, which creates new possibilities for graphdiyne’s applications in different electrochemical reactions.

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Biomass-derived bifunctional electrocatalysts for oxygen reduction and evolution reaction: A review Satpal Singh Sekhon, Jaeyoung Lee, Jin-Soo Park 2022, 65(2): 149-172.  DOI: 10.1016/j.jechem.2021.05.052 Abstract ( 19 )   PDF (7541KB) ( 6 )   Oxygen electrode catalysts are important as inter-conversion of O2 and H2O is crucial for energy technologies. However, the sluggish kinetics of oxygen reduction and evolution reactions (ORR and OER) are a hindrance to their scalable production, whereas scarce and costly Pt and Ir/Ru-based catalysts with the highest electrocatalytic activity are commercially unviable. Since good ORR catalysts are not always efficient for OER and vice versa, so bifunctional catalysts on which OER and ORR occurs on the same electrode are very desirable. Alternative catalysts based on heteroatom-doped carbon nanomaterials, though showed good electrocatalytic activity yet their high cost and complex synthesis is not viable for scalable production. To overcome these drawbacks, biomass-derived heteroatom-doped porous carbons have recently emerged as low-cost, earth-abundant, renewable and sustainable environment-friendly materials for bifunctional oxygen catalysts. The tunable morphology, mesoporous structure and high concentration of catalytic active sites of these materials due to heteroatom (N)-doping could further enhance their ORR and OER activity, along with tolerance to methanol crossover and good durability. Thus, biomass-derived heteroatom-doped porous carbons with large surface area, rich edge defects, numerous micropores and thin 2D nanoarchitecture could be suitable as efficient bifunctional oxygen catalysts. In the present article, synthesis, N-doping, ORR/OER mechanism and electrocatalytic performance of biomass-derived bifunctional catalysts has been discussed. The selected biomass (chitin, eggs, euonymus japonicas, tobacco, lysine and plant residue) except wood, act as both C and N precursor, resulting in N self-doping of porous carbons that avoids the use of toxic chemicals, thus making the synthesis a facile and environment-friendly green process. The synthetic strategy could be further optimized to develop future biomass-based N self-doped porous carbons as metal-free high performance bifunctional oxygen catalysts for commercial energy applications. Recent advances and the importance of biomass-based bifunctional oxygen catalysts in metal-air batteries and fuel cells has been highlighted. The material design, perspectives and future directions in this field are also provided.

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Optimizing side chains on different nitrogen aromatic rings achieving 17% efficiency for organic photovoltaics Zhe Li, Can Zhu, Jun Yuan, Liuyang Zhou, Wei Liu, Xinxin Xia, Juan Hong, Honggang Chen, Qingya Wei, Xinhui Lu, Yongfang Li, Yingping Zou 2022, 65(2): 173-178.  DOI: 10.1016/j.jechem.2021.05.041 Abstract ( 6 )   PDF (5332KB) ( 3 )   Balancing charge generation and low energy loss (Eloss), especially in the wide spectral absorption region is critical to obtain high-performance organic photovoltaics (OPVs). Therefore, Y11-M and Y11-EB are designed and synthesized through modifying alkyl chains on different nitrogen aromatic rings of the reported non-fullerene acceptor Y11. Although all the molecules have almost similar low band-gap (around 1.30 eV), Y11-M and Y11-EB exhibit wider absorption in 410-870 nm region. Eventually, the conventional devices based on Y11-M and Y11-EB possess more efficient charge generation with low Eloss (around 0.44 eV). In addition, outstanding efficiencies of 16.64% and 17.15% with the fill factor of 76.15% and 74.73% are obtained in PM6:Y11-M and PM6:Y11-EB-based devices, both higher than Y11:PM6. The results highlight the importance of rational alkyl chains optimization, and a good structure-property relationship is established as well.

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Preventing inhomogeneous elemental distribution and phase segregation in mixed Pb-Sn inorganic perovskites via incorporating PbS quantum dots Tao Zhang, Huaxia Ban, Qiang Sun, Han Pan, Haixuan Yu, Zhiguo Zhang, Xiaoli Zhang, Yan Shen, Mingkui Wang 2022, 65(2): 179-185.  DOI: 10.1016/j.jechem.2021.05.016 Abstract ( 6 )   PDF (9198KB) ( 2 )   Inhomogeneous Pb/Sn elemental distribution and the resulted phase segregation in mixed Pb-Sn halide perovskites would result in energy disorder (band structure and phase distribution disorder), which greatly limits their photovoltaic performance. Here, PbS quantum dot has been synthesized and demonstrated as seeds for modulation crystallization dynamics of the mixed Pb-Sn inorganic perovskites, allowing an enhanced film quality and significantly suppressing phase segregation. With this additive power conversion efficiency of 8% and 6% is obtained under irradiation of full sunlight in planar and mesoporous structured solar cells in combination with CsPb0.5Sn0.5I2Br inorganic perovskite, respectively. Our finding reveals exploring the actual Pb/Sn atoms location in perovskite structure and its influence on developing efficient and stable low-bandgap perovskite solar cells.

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Crosslinked polyacrylonitrile precursor for S@pPAN composite cathode materials for rechargeable lithium batteries Jingyu Lei, Huichao Lu, Jiahang Chen, Jun Yang, Yanna Nuli, Jiulin Wang 2022, 65(2): 186-193.  DOI: 10.1016/j.jechem.2021.05.006 Abstract ( 4 )   PDF (3281KB) ( 2 )   S@pPAN has become promising cathode materials in rechargeable batteries due to its high compressed density, low E/S ratio, no polysulfide dissolution, no self-discharge, and stable cycling. However, it is a big challenge to enhance its sulfur content which determines its practical specific capacity. Herein, we prepare crosslinked PAN as precursor, leading to effective enhancement of sulfur content up to 55 wt% and a reversible specific capacity of 838 mAh g-1composites at 0.2C. Because of the microporous structure and high specific area, crosslinked PAN provides more space to accommodate sulfur molecule and improve the interfacial reaction of S@pPAN as well. This work provides a promising direction to design S@pPAN for lithium sulfur batteries with high energy density.

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Utilizing 3,4-ethylenedioxythiophene (EDOT)-bridged non-fullerene acceptors for efficient organic solar cells Sung Jae Jeon, Young Hoon Kim, Ie Na Kim, Nam Gyu Yang, Ji Hee Yun, Doo Kyung Moon 2022, 65(2): 194-204.  DOI: 10.1016/j.jechem.2021.05.032 Abstract ( 2 )   PDF (10156KB) ( 1 )   A rational design of efficient low-band-gap non-fullerene acceptors (NFAs) for high-performance organic solar cells (OSCs) remains challenging; the main constraint being the decrease in the energy level of the lowest unoccupied molecular orbitals (LUMOs) as the bandgap of A-D-A-type NFAs decrease. Therefore, the short current density (Jsc) and open-circuit voltage (Voc) result in a trade-off relationship, making it difficult to obtain efficient OSCs. Herein, three NFAs (IFL-ED-4F, IDT-ED-4F, and IDTT-ED-2F) were synthesized to address the above-mentioned issue by introducing 3,4-ethylenedioxythiophene (EDOT) as a π-bridge. These NFAs exhibit relatively low bandgaps (1.67, 1.42, and 1.49 eV, respectively) and upshifted LUMO levels (-3.88, -3.84, and -3.81 eV, respectively) compared with most reported low-band-gap NFAs. Consequently, the photovoltaic devices based on IDT-ED-4F blended with a PBDB-T donor polymer showed the best power conversion efficiency (PCE) of 10.4% with a high Jsc of 22.1 mA cm-2 and Voc of 0.884 V among the examined NFAs. In contrast, IDTT-ED-4F, which was designed with an asymmetric structure of the D-π-A type, showed the lowest efficiency of 1.5% owing to the poor morphology and charge transport properties of the binary blend. However, when this was introduced as the third component of the PM6:BTP-BO-4Cl, complementary absorption and cascade energy-level alignment between the two substances could be achieved. Surprisingly, the IDTT-ED-4F-based ternary blend device not only improved the Jsc and Voc, but also achieved a PCE of 15.2%, which is approximately 5.3% higher than that of the reference device with a minimized energy loss of 0.488 eV. In addition, the universality of IDTT-ED-2F as a third component was effectively demonstrated in other photoactive systems, specifically, PM6:BTP-eC9 and PTB7-Th:IEICO-4F. This work facilitates a better understanding of the structure-property relationship for utilizing efficient EDOT-bridged NFAs in high-performance OSC applications.

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Hybridized S cathode with N719 dye for a photo-assisted charging Li-S battery Jingfa Li, Changwei Ren, Linbiao Zhang, Wenhao Jiang, Hongmin Liu, Jing Su, Min Li 2022, 65(2): 205-209.  DOI: 10.1016/j.jechem.2021.05.044 Abstract ( 23 )   PDF (2136KB) ( 18 )

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High temperature X-ray diffraction study of the formation of Na2Ti3O7 from a mixture of sodium carbonate and titanium oxide Caroline Piffet, Bénédicte Vertruyen, Frédéric Hatert, Rudi Cloots, Frédéric Boschini, Abdelfattah Mahmoud 2022, 65(2): 210-218.  DOI: 10.1016/j.jechem.2021.05.050 Abstract ( 7 )   PDF (9474KB) ( 3 )   Na2Ti3O7 has attracted much attention in the field of anode materials for Na-ion batteries thanks to its non-toxicity and very low working potential of 0.3 V vs Na0/Na+. Building a clearer picture of its formation from cheap Na2CO3 and TiO2 starting materials is therefore of obvious interest. Here, we report new insights from an in-situ high temperature X-ray diffraction study conducted from room temperature to 800 °C, complemented by ex-situ characterizations. We were thereby able to position the previously reported Na4Ti5O12 and Na2Ti6O13 intermediate phases in a reaction scheme involving three successive steps and temperature ranges. Shifts and/or broadening of a subset of the Na2Ti6O13 reflections suggested a combination of intra-layer disorder with the well-established ordering of successive layers. This in-situ study was carried out on reproducible mixtures of Na2CO3 and TiO2 in 1:3 molar ratio prepared by spray-drying of mixed aqueous suspensions. Single-phase Na2Ti3O7 was obtained after only 8 h at 800 °C in air, instead of a minimum of 20 h for a conventional solid-state route using the same precursors. Microstructure analysis revealed ~ 15 µm diameter granules made up from rectangular rods of a few-µm length presenting electrochemical properties in line with expectations. In the absence of grinding or formation of intimate composites with conductive carbon, the specific capacity of 137 mAh/g at C/5 decreased at higher rates.

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Recent strategies to improve moisture stability in metal halide perovskites materials and devices Chenxiao Zhou, Alexey B. Tarasov, Eugene A. Goodilin, Pengwan Chen, Hao Wang, Qi Chen 2022, 65(2): 219-235.  DOI: 10.1016/j.jechem.2021.05.035 Abstract ( 8 )   PDF (21958KB) ( 1 )   At present, the stability of the new generation of solar cells based on hybrid perovskites is the bottleneck for their practical applications. Photochemical effects, high temperature, ultraviolet light, humidity and other known or still unknown factors might cause reduction of effectiveness or even irreversible loss of materials properties due to decomposition of functional layers within perovskite solar cells (PSCs). These factors alone have a serious impact on each component of the device, while their combinations lead to much more complicated effects and consequences. This review focuses on the stability of PSCs and the degradation of the device in a humid environment. We assess the instability factors and deep-seated principles of evolution of the device structure in a humidity environment with the emphasis on the influence on their interrelations. The related solutions are reviewed from the perspective of the encapsulation, perovskite active layer, carrier transport layer and electrodes. Combined with the latest research, we believe that the waterproof strategy of PSCs requires either tight encapsulation or thorough modifications in the device itself. Therefore, it is important to develop feasible strategies to improve the overall device stability over humid according to the target characteristics of various devices.

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Stress accumulation in Ni-rich layered oxide cathodes: Origin, impact, and resolution Yuefeng Su, Qiyu Zhang, Lai Chen, Liying Bao, Yun Lu, Shi Chen, Feng Wu 2022, 65(2): 236-253.  DOI: 10.1016/j.jechem.2021.05.048 Abstract ( 10 )   PDF (13061KB) ( 7 )   LiNixCoyMnzO2 (NCM, x + y + z = 1) is one of the most promising cathode candidates for high energy density lithium-ion batteries (LIBs). Due to the potential in enhancing energy density and cyclic life of LIBs, Ni-rich layered NCM (NCM, x ≥ 0.6) have garnered significant research attention. However, improved specific capacity lead to severer expansion and shrinkage of layered lattice, accelerating the stress generation and accumulation even microcracks formation in NCM materials. The microcracks can promote the electrolyte permeation and decomposition, which can consequently reduce cyclic stabilities. Therefore, it is significant to provide an in-depth insight into the origin and impacts of stress accumulation, and the available modification strategies for the future development of NCM materials. In this review, we will first summarize the origin of stress accumulation in NCM materials. Next, we discuss the impact of stress accumulation. The electrolyte permeation along microcracks can enhance the extent of side reaction at the interface, trigger phase transformation and consequential capacity fading. To cushion the impact of stress accumulation, we will review five main strategies. Finally, concise perspectives to reduce stress accumulation and enhance particle strength in further works will be presented.

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Single-atom catalysts for CO oxidation, CO2 reduction, and O2 electrochemistry Wenyu Yuan, Yiyuan Ma, Heng Wu, Laifei Cheng 2022, 65(2): 254-279.  DOI: 10.1016/j.jechem.2021.05.046 Abstract ( 10 )   PDF (28971KB) ( 3 )   COx (x = 1, 2) and O2 chemistry play key roles in tackling global severe environmental challenges and energy issues. To date, the efficient selective electrocatalytic transformations of COx-carbon chemicals, and O2-hydrogenated products are still huge challenges. Single-atom catalysts (SACs) as atomic-scale novel catalysts in which only isolated metal atoms are dispersed on supports shed new insights in overcome these obstacles in COx and O2 chemistry, including CO oxidation, CO2 reduction reaction (CO2RR), oxygen reduction reaction (ORR), and oxygen evolution reaction (OER). In this review, the unique features and advanced synthesis strategies of SACs from a viewpoint of fundamental synthesis design are first highlighted to guide future strategy design for controllable SAC synthesis. Then, the to-date reported CO2RR, CO oxidation, OER, and ORR mechanism are included and summarized. More importantly, the design principles and design strategies of improving the intrinsic activity, selectivity, and stability are extensively discussed and the engineering strategy is classified as neighbor coordination engineering, metal-atom engineering, and substrate engineering. Via the comprehensive review and summary of state-of-the-art SACs, the synthesis - structure - property - mechanism - design principle relation can be revealed to shed lights into the structural construction of SACs. Finally, we present an outlook on current challenges and future directions for SACs in COx and O2 chemistry.

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Recent progress on electrolyte functional additives for protection of nickel-rich layered oxide cathode materials Longshan Li, Dingming Wang, Gaojie Xu, Qian Zhou, Jun Ma, Jianjun Zhang, Aobing Du, Zili Cui, Xinhong Zhou, Guanglei Cui 2022, 65(2): 280-292.  DOI: 10.1016/j.jechem.2021.05.049 Abstract ( 4 )   PDF (8382KB) ( 2 )   In advantages of their high capacity and high operating voltage, the nickel (Ni)-rich layered transition metal oxide cathode materials (LiNixCoyMnzO2 (NCMxyz, x + y + z = 1, x ≥ 0.5) and LiNi0.8Co0.15Al0.05O2 (NCA)) have been arousing great interests to improve the energy density of LIBs. However, these Ni-rich cathodes always suffer from rapid capacity degradation induced by unstable cathode-electrolyte interphase (CEI) layer and destruction of bulk crystal structure. Therefore, varied electrode/electrolyte interface engineering strategies (such as electrolyte formulation, material coating or doping) have been developed for Ni-rich cathodes protection. Among them, developing electrolyte functional additives has been proven to be a simple, effective, and economic method to improve the cycling stability of Ni-rich cathodes. This is achieved by removing unfavorable species (such as HF, H2O) or constructing a stable and protective CEI layer against unfavorable reactive species (such as HF, H2O). Herein, this review mainly introduces the varied classes of electrolyte functional additives and their working mechanism for interfacial engineering of Ni-rich cathodes. Especially, key favorable species for stabilizing CEI layer are summarized. More importantly, we put forward perspectives for screening and customizing ideal functional additives for high performance Ni-rich cathodes based LIBs.

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Pt-Sn clusters anchored at Al3+penta sites as a sinter-resistant and regenerable catalyst for propane dehydrogenation Xinyue Zhu, Tinghai Wang, Zhikang Xu, Yuanyuan Yue, Minggui Lin, Haibo Zhu 2022, 65(2): 293-301.  DOI: 10.1016/j.jechem.2021.06.002 Abstract ( 7 )   PDF (2959KB) ( 2 )   Pt-based catalysts are widely used in propane dehydrogenation reaction for the production of propylene. Suppressing irreversible deactivation caused by the sintering of Pt particles under harsh conditions and regeneration process is a significant challenge in this catalyst. Herein, a series of highly ordered mesoporous Al2O3 supports with different levels of Al3+penta sites, are fabricated and used as the support to disperse Pt-Sn2 clusters. Characterizations of Pt-Sn2/meso-Al2O3 with XRD, NMR, CO-IR, STEM, TG, and Raman techniques along with propane dehydrogenation-regeneration cycles test reveal the structure-stability-regenerability relationship. The coordinatively unsaturated pentacoordinate Al3+ (Al3+penta) can strongly anchor Pt atoms via a formation of Al-O-Pt bond, and thus stabilize the Pt-based particles at the surface of Al2O3. The stability and regenerability of Pt-Sn2/meso-Al2O3 are strongly dependent on the content of Al3+penta sites in the Al2O3 structure, and a high level of Al3+penta sites can effectively prevent the agglomeration of Pt-Sn2 clusters into large Pt nanoparticles in the consecutive dehydrogenation-regeneration cycles. The Pt-Sn2/meso-Al2O3-600 with the highest level of Al3+penta (50.8%) delivers the best performance in propane dehydrogenation, which exhibits propane conversion of 40% and propylene selectivity above 98% at 570 °C with 10 vol% C3H8 and 10 vol% H2 feed. A slow deactivation in this catalyst is ascribed to the formation of coke, and the catalytic performance can be fully restored in the consecutive dehydrogenation-regeneration cycles via a simple calcination treatment.

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One stone two birds: Dual-effect kinetic regulation strategy for practical lithium-sulfur batteries Xi-Yao Li, Qiang Zhang 2022, 65(2): 302-303.  DOI: 10.1016/j.jechem.2021.05.039 Abstract ( 7 )   PDF (1496KB) ( 2 )

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Co-catalyst-free large ZnO single crystal for high-efficiency piezocatalytic hydrogen evolution from pure water Biao Wang, Qian Zhang, Jiaqing He, Feng Huang, Caifu Li, Mengye Wang 2022, 65(2): 304-311.  DOI: 10.1016/j.jechem.2021.06.004 Abstract ( 10 )   PDF (4323KB) ( 9 )   Piezocatalytic materials have been widely used for catalytic hydrogen evolution and purification of organic contaminants. However, most studies focus on nano-size and/or polycrystalline catalysts, suffering from aggregation and neutralization of internal piezoelectric field caused by polydomains. Here we report a single crystal ZnO of large size and few bulk defects crafted by a hydrothermal method for piezocatalytic hydrogen generation from pure water. It is noteworthy that single-side surface areas of both original as-prepared ZnO and Ga-doped ZnO bulk crystals are larger than 30 cm2. The high quality of ZnO and Ga-doped ZnO bulks are further uncovered by high-resolution transmission electron microscope (HRTEM), photoluminescence (PL) and X-ray diffraction (XRD). Remarkably, an outstanding hydrogen production rate of co-catalyst-free Ga-doped ZnO bulk crystal (i.e., a maximum rate of 5915 μmol h-1 m-2) is observed in pure water triggered by ultrasound in dark, which is over 100 times higher than that of its powder counterpart (i.e., 52.54 μmol h-1 m-2). The piezocatalytic performance of ZnO bulk crystal is systematically studied in terms of varied exposed crystal facet, thickness and conductivity. Different piezocatalytic performances are attributed to magnitude and distribution of piezoelectric potential, revealed by the finite element method (FEM) simulation. The density functional theory (DFT) calculations are employed to investigate the piezocatalytic hydrogen evolution process, indicating a strong H2O adsorption and a low energy barrier for both H2O dissociation and H2 generation on the stressed Zn-terminated (0001) ZnO surface.

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Highly stable perovskite solar cells with a novel Ni-based metal organic complex as dopant-free hole-transporting material Tai Wu, Linqin Wang, Rongjun Zhao, Rongshan Zhuang, Kanghong Zhao, Gaoyuan Liu, Jing Huang, Licheng Sun, Yong Hua 2022, 65(2): 312-318.  DOI: 10.1016/j.jechem.2021.06.005 Abstract ( 10 )   PDF (3169KB) ( 2 )   Hole-transporting material (HTM) plays a paramount role in enhancing the photovltaic performance of perovskite solar cells (PSCs). Currently, the vast majority of these HTMs employed in PSCs are organic small molecules and polymers, yet the use of organic metal complexes in PSCs applications remains less explored. To date, most of reported HTMs require additional chemical additives (e.g. Li-TFSI, t-TBP) towards high performance, however, the introduction of additives decrease the PSCs device stability. Herein, an organic metal complex (Ni-TPA) is first developed as a dopant-free HTM applied in PSCs for its facile synthesis and efficient hole extract/transfer ability. Consequently, the dopant-free Ni-TPA-based device achieves a champion efficiency of 17.89%, which is superior to that of pristine Spiro-OMeTAD (14.25%). Furthermore, we introduce a double HTM layer with a graded energy bandgap containing a Ni-TPA layer and a CuSCN layer into PSCs, the non-encapsulated PSCs based on the Ni-TPA/CuSCN layers affords impressive efficiency up to 20.39% and maintains 96% of the initial PCE after 1000 h at a relative humidity around 40%. The results have demonstrated that metal organic complexes represent a great promise for designing new dopant-free HTMs towards highly stable PSCs.

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LiF and LiNO3 as synergistic additives for PEO-PVDF/LLZTO-based composite electrolyte towards high-voltage lithium batteries with dual-interfaces stability Liansheng Li, Yuanfu Deng, Huanhuan Duan, Yunxian Qian, Guohua Chen 2022, 65(2): 319-328.  DOI: 10.1016/j.jechem.2021.05.055 Abstract ( 9 )   PDF (4611KB) ( 3 )   Solid electrolytes with desirable properties such as high ionic conductivity, wide electrochemical stable window, and suitable mechanical strength, and stable electrode-electrolyte interfaces on both cathode and anode side are essential for high-voltage all-solid-state lithium batteries (ASSLBs) to achieve excellent cycle stability. In this work, a novel strategy of using LiF and LiNO3 as synergistic additives to boost the performance of PEO-PVDF/LLZTO-based composite solid electrolytes (CSEs) is developed, which also promotes the assembled high-voltage ASSLBs with dual-interfaces stability characteristic. Specifically, LiF as an inactive additive can increase the electrochemical stability of the CSE under high cut-off voltage, and improve the high-voltage compatibility between cathode and CSE, thus leading to a stable cathode/CSE interface. LiNO3 as an active additive can lead to an enhanced ionic conductivity of CSE due to the increased free-mobile Li+ and ensure a stable CSE/Li interface by forming stable solid electrolyte interphase (SEI) on Li anode surface. Benefiting from the improved performance of CSE and stable dual-interfaces, the assembled NCM622/9[PEO15-LiTFSI]-PVDF-15LLZTO-2LiF-3LiNO3/Li cell delivers a high rate capacity of 102.1 mAh g-1 at 1.0 C and a high capacity retention of 77.4% after 200 cycles at 0.5 C, which are much higher than those of the ASSLB assembled with additive-free CSE, with only 60.0 mAh g-1 and 52.0%, respectively. Furthermore, novel cycle test modes of resting for 5 h at different charge states after every 5 cycles are designed to investigate the high-voltage compatibility between cathode and CSE, and the results suggest that LiF additive can actually improve the high-voltage compatibility of cathode and CSE. All the obtained results confirm that the strategy of using synergistic additives in CSE is an effective way to achieve high-voltage ASSLBs with dual-interfaces stability.

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Trimetallic nanostructures and their applications in electrocatalytic energy conversions Shushay Hagos Gebre, Marshet Getaye Sendeku 2022, 65(2): 329-351.  DOI: 10.1016/j.jechem.2021.06.006 Abstract ( 5 )   PDF (18661KB) ( 3 )   The advancement and growth of nanotechnology lead to realizing new and novel multi-metallic nanostructures with well-defined sizes and morphology, resulting in an improvement in their performance in various catalytic applications. The trimetallic nanostructured materials are synthesized and designed in different architectures for energy conversion electrocatalysis. The as-synthesized trimetallic nanostructures have found unique physiochemical properties due to the synergistic combination of the three different metals in their structures. A vast array of approaches such as hydrothermal, solvothermal, seed-growth, galvanic replacement reaction, biological, and other methods are employed to synthesize the trimetallic nanostructures. Noteworthy, the trimetallic nanostructures showed better performance and durability in the electrocatalytic fuel cells. In the present review, we provide a comprehensive overview of the recent strategies employed for synthesizing trimetallic nanostructures and their energy-related applications. With a particular focus on hydrogen evolution, alcohol oxidations, oxygen evolution, and others, we highlight the latest achievements in the field.

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Small dissymmetry, yet large effects on the transport properties of electrolytes based on imide salts: Consequences on performance in Li-ion batteries Joseph Chidiac, Laure Timperman, Mérièm Anouti 2022, 65(2): 352-366.  DOI: 10.1016/j.jechem.2021.05.054 Abstract ( 4 )   PDF (14954KB) ( 2 )   To gain better insight into the influence of the anion size and symmetry on the transport properties and thermal stability of an electrolyte based on lithium (fluorosulfonyl)(trifluoromethanesulfonyl)-imide (FTFSI) salt, we performed the physical and electrochemical characterization of an electrolyte based on FTFSI incorporated in standard binary (3EC/7EMC) and ternary (EC/PC/3DMC) alkylcarbonate mixtures. By applying the Jones-Dole-Kaminsky (JDK), Eyring and Arrhenius empirical models to the electrolyte viscosity we show that the activation enthalpy and entropy energy barriers ($\Delta H^{\neq}, \Delta S^{\neq}$) for viscous flow are between 12 and 15 kJ·mol-1. They are strongly dependent on the solvent nature and are significantly lower than their symmetric anions LiFSI and LiTFSI (19-20 kJ·mol-1) in the binary mixture. Furthermore, the hydrodynamic radius, rs, calculated by JDK, and the ionicity behavior illustrated by the Walden role, showed that the FTFSI anion is outside the solvation sphere (rs > 0.6 nm) which is smaller in the case of an EC/EMC solvent base. In the 3EC/7EMC solvent mixture, LiFTFSI is less conductive than in the ternary mixture i.e., σmax = 8.9 mS cm-1 at Cmax = 1.1 mol L-1 for 3EC/7EMC and, σmax = 10.5 mS cm-1 at max = 0.7 mol L-1 for EC/PC/3DMC, due to a strong solvation and a greater association of FTFSI ions in the binary solvent mixture. The thermal stability of FTFSI based electrolytes was determined by the shift of the evaporation temperature of the volatile solvents (DMC, EMC) in the presence of salt, towards the higher temperatures. This feature is visible on the thermograms obtained by DSC both with the liquid electrolyte and with charged LMO cathodes in presence of electrolytes. The consequences of these properties on the electrochemical behavior of a graphite (Gr) half-cell, a lithium metal (Li) anode and a manganese lithium oxide (LMO) cathode demonstrated on the one hand the formation of a thick solid electrolyte interphase (SEI) on graphite that consumed a significant amount of lithium i.e., 18% of total capacity of the first charge. Furthermore, LiFTFSI delivered 95% of the initial capacity C = 360 mAh g-1 at C/10 with EC/PC/3DMC versus 91% when it was combined with 3EC/7EMC C = 348 mAh g-1, while the capacities obtained for LiTFSI in EC/PC/3DMC were the lowest (C = 275 mAh g-1) compared to those of the other salts. After 10 cycles, the capacity loss at C/20 is <2% for LiFSI and LiFTFSI with the two solvent mixtures. On the other hand, manganese dissolution from LMO as well as current collector corrosion were confirmed by post-mortem examination of opened coin cells. The incompatibility of the LMO cathode with an electrolyte based on FTFSI was confirmed by the position of the decomposition peak of charged LMO in contact with this electrolyte observed by DSC. These results demonstrate that the nature of the anion as well as the composition of the solvent considerably influence the performance of imide-based lithium salts both on the anode, but especially on the high voltage cathode.

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Cascade electrocatalytic reduction of carbon dioxide and nitrate to ethylamine Zixu Tao, Yueshen Wu, Zishan Wu, Bo Shang, Conor Rooney, Hailiang Wang 2022, 65(2): 367-370.  DOI: 10.1016/j.jechem.2021.06.007 Abstract ( 16 )   PDF (4304KB) ( 8 )

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Stability of Sn-Pb mixed organic-inorganic halide perovskite solar cells: Progress, challenges, and perspectives Shaoshen Lv, Weiyin Gao, Yanghua Liu, He Dong, Nan Sun, Tingting Niu, Yingdong Xia, Zhongbin Wu, Lin Song, Chenxin Ran, Li Fu, Yonghua Chen 2022, 65(2): 371-404.  DOI: 10.1016/j.jechem.2021.06.011 Abstract ( 23 )   PDF (46382KB) ( 13 )   The exploration of low bandgap perovskite material to approach Shockley-Queisser limit of photovoltaic device is of great significance, but it is still challenging. During the past few years, tin-lead (Sn-Pb) mixed perovskites with low bandgaps have been rapidly developed, and their single junction solar cells have reached power conversion efficiency (PCE) over 21%, which also makes them ideal candidate as low bandgap sub-cell for tandem device. Nevertheless, due to the incorporation of unstable Sn2+, the stability issue becomes the vital problem for the further development of Sn-Pb mixed perovskite solar cells (PSCs). In this review, we are dedicated to give a full view in current understanding on the stability issue of Sn-Pb mixed perovskites and their PSCs. We begin with the demonstration on the origin of instability of Sn-Pb mixed perovskites, including oxidation of Sn2+, defects, and interfacial layer induced instability. Sequentially, the up-to-date developments on the stability improvement of Sn-Pb mixed perovskites and their PSCs is systematically reviewed, including composition engineering, additive engineering, and interfacial engineering. At last, the current challenges and future perspectives on the stability study of Sn-Pb mixed PSCs are discussed, which we hope could promote the further application of Sn-Pb mixed perovskites towards commercialization.

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Remarkable synergistic effect in cobalt-iron nitride/alloy nanosheets for robust electrochemical water splitting Mingpeng Chen, Di Liu, Baoye Zi, Yuyun Chen, Dong Liu, Xinyu Du, Feifei Li, Pengfei Zhou, Ye Ke, Jielei Li, Kin Ho Lo, Chi Tat Kwok, Weng Fai Ip, Shi Chen, Shuangpeng Wang, Qingju Liu, Hui Pan 2022, 65(2): 405-414.  DOI: 10.1016/j.jechem.2021.05.051 Abstract ( 7 )   PDF (12302KB) ( 1 )   Design and synthesis of noble-metal-free bifunctional catalysts for efficient and robust electrochemical water splitting are of significant importance in developing clean and renewable energy sources for sustainable energy consumption. Herein, a simple three-step strategy is reported to construct cobalt-iron nitride/alloy nanosheets on nickel foam (CoFe-NA/NF) as a bifunctional catalyst for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The electrocatalyst with optimized composition (CoFe-NA2/NF) can achieve ultralow overpotentials of 73 mV and 250 mV for HER and OER, respectively, at a current density of 10 mA cm-2 in 1 M KOH. Notably, the electrolyzer based on this electrocatalyst is able to boost the overall water splitting with a cell voltage of 1.564 V to deliver 10 mA cm-2 for at least 50 h without obvious performance decay. Furthermore, our experiment and theoretical calculation demonstrate that the combination of cobalt-iron nitride and alloy can have low hydrogen adsorption energy and facilitate water dissociation during HER. In addition, the surface reconstruction introduces metal oxyhydroxides to optimize the OER process. Our work may pave a new pathway to design bifunctional catalysts for overall water splitting.

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Self-motivated, thermally oxidized hematite nanoflake photoanodes: Effects of pre-polishing and ZrO2 passivation layer Love Kumar Dhandole, Hyun Hwi Lee, Weon-Sik Chae, Jum Suk Jang, Jae Sung Lee 2022, 65(2): 415-423.  DOI: 10.1016/j.jechem.2021.06.009 Abstract ( 7 )   PDF (5713KB) ( 1 )   High-temperature thermal oxidation of an Fe foil produces a high-quality, crystalline hematite nanoflake suitable as a photoanode for the photoelectrochemical (PEC) water oxidation. Physical pre-polishing of the foil surface has a profound effect in the formation of a vertically-aligned nanoflakes of hematite phase with extended (110) planes by removing the loosely-bonded oxide layer. When the surface of the photoanode is modified with a ZrO2 passivation layer and a cobalt phosphate co-catalyst, the charge recombination at the photoanode-electrolyte interface is greatly suppressed to improve its overall PEC activity. As a result, the photocurrent density at 1.10 VRHE under 1 sun condition is enhanced from 0.22 mA cm-2 for an unmodified photoanode to 0.59 mA cm-2 for the fully modified photoanode, and the photocurrent onset potential is shifted cathodically by 400 mV. Moreover, the photoanode demonstrates outstanding stability by showing steady production of H2 and O2 gases in the stoichiometric ratio of 2:1 in a continuous PEC operation for 10 h.

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Insight into the structural evolution and thermal behavior of LiNi0.8Co0.1Mn0.1O2 cathode under deep charge Chen Liang, Lihua Jiang, Zesen Wei, Wenhua Zhang, Qingsong Wang, Jinhua Sun 2022, 65(2): 424-432.  DOI: 10.1016/j.jechem.2021.06.010 Abstract ( 15 )   PDF (7191KB) ( 11 )   By virtue of the crucial effect of the crystal structure and transition metal (TM) redox evolution on the performance of LiNixCoyMnzO2 (NCM) cathode, systematical investigation is carried out to better understand the charge mechanism upon deep charging. Based on the results of X-ray diffraction and high-resolution transmission electron microscope, phase transformations existing on particle surface are promoted by high potential because of the deeper lithium vacancies, accompanied by more substantial structure instability. Soft X-ray absorption spectroscopy indicates that Ni acts as the major contributor to charge compensation while Co displays a remarkable redox activity over the deep charge range. The elevated integrated intensity of pre-edge in O K-edge spectra reveals the extensive amount of holes formed in O 2p orbitals and the enhanced hybridization of TM 3d - O 2p orbitals. Considering the close relationship between thermal behavior and structural evolution, the tendency of phase transitions and O2 release upon heating is accelerated by voltage rise, demonstrating the aggravated instability due to deeper Li utilization. Remaining Li contents in NCM are employed to estimate the amount of oxygen released in structural transformation and its detrimental effect on stability declares Li content-dependent characteristics. Furthermore, the extended Li vacancies, higher proportion of Ni4+ and stronger orbital hybridization are considered as three factors impeding the thermal stability of the highly-delithiated NCM.

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Reduced formation of peroxide and radical species stabilises iron-based hybrid catalysts in polymer electrolyte membrane fuel cells Dongyoon Shin, Sabita Bhandari, Marc F. Tesch, Shannon A. Bonke, Frédéric Jaouen, Sonia Chabbra, Christoph Pratsch, Alexander Schnegg, Anna K. Mechler 2022, 65(2): 433-438.  DOI: 10.1016/j.jechem.2021.05.047 Abstract ( 8 )   PDF (1336KB) ( 4 )   The incorporation of Pt into an iron-nitrogen-carbon (FeNC) catalyst for the oxygen reduction reaction (ORR) was recently shown to enhance catalyst stability without Pt directly contributing to the ORR activity. However, the mechanistic origin of this stabilisation remained obscure. It is established herein with rotating ring disc experiments that the side product, H2O2, which is known to damage FeNC catalysts, is suppressed by the presence of Pt. The formation of reactive oxygen species is additionally inhibited, independent of intrinsic H2O2 formation, as determined by electron paramagnetic resonance. Transmission electron microscopy identifies an oxidised Fe-rich layer covering the Pt particles, thus explaining the inactivity of the latter towards the ORR. These insights develop understanding of FeNC degradation mechanisms during ORR catalysis, and crucially establish the required properties of a precious metal free protective catalyst to improve FeNC stability in acidic media.

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Synergistic effect of lithiophilic Zn nanoparticles and N-doping for stable Li metal anodes Lei You, Shunlong Ju, Jianwen Liu, Guanglin Xia, Zaiping Guo, Xuebin Yu 2022, 65(2): 439-447.  DOI: 10.1016/j.jechem.2021.06.001 Abstract ( 10 )   PDF (8033KB) ( 2 )   Li metal is the most ideal anode material for next-generation high energy lithium-ion batteries. The uncontrollable growth of Li dendrites, however, hinders its practical application. Herein, we propose the adoption of Zn nanoparticles uniformly embedded in N-doped carbon polyhedra homogeneously built on carbon cloth (Zn@NC@CC) to prevent the formation of Li dendrites. Based on theoretical calculation and experimental observation, lithiophilic Zn nanoparticles and N-doping inside of the as-synthesized Zn@NC play a synergistic role in enhancing the adsorption capacity with Li, thus resulting in uniform Li deposition and complete suppression of Li dendrites. Moreover, the porous N-doped carbon polyhedras uniformly distributed on carbon cloth effectively relieves the volume change of Li upon repeated Li stripping/plating process, which contributes to preserving the structural integrity of the whole electrode and hence enhancing its long-term cycling stability. Benefiting from these synergistic effects, the Li-Zn@NC@CC electrode delivers a prolonged lifespan of over 1200 h at 1 mA cm-2 with an areal capacity of 1 mA h cm-2 in symmetric cells and high Coulombic efficiencies of 95.4% under an ultrahigh capacity of 12 mA h cm-2. Remarkably, Li-Zn@NC@CC//LiFePO4 full cells deliver a high reversible capacity of 110.2 mA h g-1 at 1C over 200 cycles.

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Defect and interface engineering for electrochemical nitrogen reduction reaction under ambient conditions Dongxue Guo, Shuo Wang, Jun Xu, Wenjun Zheng, Danhong Wang 2022, 65(2): 448-468.  DOI: 10.1016/j.jechem.2021.06.012 Abstract ( 7 )   PDF (9594KB) ( 2 )   Electrochemical nitrogen reduction reaction (e-NRR) under ambient conditions is an emerging strategy to tackle the hydrogen- and energy-intensive operations for traditional Haber-Bosch process in industrial ammonia (NH3) synthesis. However, the e-NRR performance is currently impeded by the inherent inertness of N2 molecules, the extremely slow kinetics and the overwhelming competition from the hydrogen evolution reaction (HER), all of which cause unsatisfied yield and ammonia selectivity (Faradaic efficiency, FE). Defect and interface engineering are capable of achieving novel physical and chemical properties as well as superior synergistic effects for various electrocatalysts. In this review, we first provide a general introduction to the NRR mechanism. We then focus on the recent progress in defect and interface engineering and summarize how defect and interface can be rationally designed and functioned in NRR catalysts. Particularly, the origin of superior NRR catalytic activity by applying these approaches was discussed from both theoretical and experimental perspectives. Finally, the remaining challenges and future perspectives in this emerging area are highlighted. It is expected that this review will shed some light on designing NRR electrocatalysts with excellent activity, selectivity and stability.

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Novel phosphonated polymer without anhydride formation for proton exchange membrane fuel cells Mrinmay Mandal 2022, 65(2): 469-471.  DOI: 10.1016/j.jechem.2021.06.013 Abstract ( 8 )   PDF (2503KB) ( 4 )

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Regulating the nucleation of Li2CO3 and C by anchoring Li-containing carbonaceous species towards high performance Li-CO2 batteries Shiyu Ma, Youcai Lu, Hongchang Yao, Yubing Si, Qingchao Liu, Zhongjun Li 2022, 65(2): 472-479.  DOI: 10.1016/j.jechem.2021.06.016 Abstract ( 4 )   PDF (5529KB) ( 3 )   Li-CO2 batteries provide an attractive and potential strategy for CO2 utilization as well as energy conversion and storage with high specific energy densities. However, the poor reversibility caused by the decomposition obstacles of Li2CO3 and C products is still a challenge for Li-CO2 batteries, which seriously influences its electrochemical performances. Herein, a free-standing MnOOH arrays cathode has been prepared and employed in Li-CO2 battery, which realizes a great improvement of electrochemical performances by adjusting the discharge products distribution. Experiments coupled with theoretical calculations verifies that the formation of Li-containing carbonaceous species (LiCO2, LiCO and Li2CO3) bonded with MnOOH through Li ion regulates the nucleation behavior of Li2CO3 and C, making them grown on MnOOH uniformly. The fine Li2CO3 grains (with a size about 5 nm) embedded into carbon matrix greatly enlarges the contact interface between them, facilitating the transmission of electrons through the discharge products and finally improves CO2 evolution activity. This ingenious design strategy of regulating discharge products distribution to improve electrochemical performances provides a promising way to develop advanced Li-CO2 batteries.

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Graded 2D/3D (CF3-PEA)2FA0.85MA0.15Pb2I7/FA0.85MA0.15PbI3 heterojunction for stable perovskite solar cell with an efficiency over 23.0% Yuan Cai, Jialun Wen, Zhike Liu, Fang Qian, Chenyang Duan, Kun He, Wenjing Zhao, Sheng Zhan, Shaomin Yang, Jian Cui, ShengzhongLiu 2022, 65(2): 480-489.  DOI: 10.1016/j.jechem.2021.05.042 Abstract ( 6 )   PDF (10423KB) ( 1 )   The replacement of small cations with bulkier organic cations containing long alkyl chains or benzene rings to form a thin two-dimensional (2D) perovskite passivation layer on three-dimensional (3D) perovskite (2D/3D) has become a promising strategy for improving both the efficiency and stability of perovskite solar cells (PSCs). The 2D layer defines the interfacial chemistry and physics at the 2D/3D bilayer and endows the 2D/3D structure with better chemical and thermal stability. Herein, 2D/3D (CF3-PEA)2FA0.85MA0.15Pb2I7/FA0.85MA0.15PbI3 planar heterojunction perovskite was produced using a facile interfacial ion exchange process. The 2D (CF3-PEA)2FA0.85MA0.15Pb2I7 capping layer can not only passivate the FA0.85MA0.15PbI3 film but also act as super-hydrophobic layer to inhibit water diffusion and significantly enhance the stability. The 2D capping layer can also establish a unique graded band structure at the perovskite/Spiro-OMeTAD interface and lead to p-type doping for Spiro-OMeTAD layer which is beneficial for efficient charge transport. Optimized PSCs based on this 2D/3D heterojunction yield a champion power conversion efficiency (PCE) of 23.1% and improved stability. The device maintains 84% output for 2400 h aging under ambient environmental conditions without encapsulation, and maintains 81% for 200 h under illumination with encapsulation. This work will inspire the design of more fluorinated 2D perovskite interfaces for advanced photovoltaics and beyond.

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Substituent engineering of covalent organic frameworks modulates the crystallinity and electrochemical reactivity Jing Ning, Yang Gao, Xingdi Cao, Hongtao Wei, Bin Wang, Long Hao 2022, 65(2): 490-496.  DOI: 10.1016/j.jechem.2021.06.014 Abstract ( 8 )   PDF (4692KB) ( 3 )   Covalent organic frameworks (COFs) are emerging as powerful electrochemical energy storage/conversion materials benefiting from the controlled pore and chemical structures, which are usually determined by the regulation of the molecular building blocks. In contrast, the substituents are not considered significant for the electrochemical reactivity as they are usually removed during carbonization, which is necessary for improving the electrical conductivity of an electrode material. Here we show that the substituents play key roles not only in synthesizing COFs but also in controlling the COF structures during carbonization and thus the related electrochemical reactivity. Five characteristic substituents were used when synthesizing a new COF structure and it was found that electron-withdrawing strength of the substituents significantly influences the crystallinity of the COFs by tuning the reactivity of building blocks, or even determines whether the crystalline COF can be constructed. Moreover, the differences in chemical groups, sizes, and thermal stabilities of the substituents result in varied pore-collapse behaviors and the structures of the carbonized COFs, which show diverse effects on the electrochemical performances. An optimal material shows the highest surface area of 2131 m2/g, rich pores around 1 nm, and the highest ratio of sp2 carbon among the samples, corresponding to the largest double-layer specific capacity over 125 F/g in an ionic liquid electrolyte, while another material with the lowest surface area and N-doping level exhibits a high H2O2 production selectivity over 80% through selective oxygen reduction. This study shows guiding significance for the design of building blocks and substituents for COFs and further the carbonized carbons, and also exhibits the great potential of substituent engineering in modulating the electrochemical reactivity.

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CuSx-mediated two reaction systems enable biomimetic photocatalysis in CO2 reduction with visible light Ling-Xiang Wang, Zhi-Qiang Wang, Liang Wang, Zhiyuan Yang, Qiuyan Zhu, Yifeng Liu, Wei Fang, Xue-Qing Gong, Yuefeng Liu, Xiaolong Liu, Feng-Shou Xiao 2022, 65(2): 497-504.  DOI: 10.1016/j.jechem.2021.06.003 Abstract ( 7 )   PDF (7411KB) ( 2 )   The performances of heterogeneous catalysts can be effectively improved by optimizing the catalysts via appropriate structure design. Herein, we show that the catalysis of cuprous sulfide can be boosted by constructing the hybrid structure with Cu2S nanoparticles on amorphous CuSx matrix (Cu2S/CuSx). In the photocatalytic CO2 reduction under visible light irradiation, the Cu2S/CuSx exhibited a CO production rate at 4.0 µmol h-1 that is 12-fold higher than that of the general Cu2S catalyst. Further characterizations reveal that the Cu2S/CuSx has two reaction systems that realize the biomimetic catalysis, involving in the light reaction on the Cu2S nanoparticle-CuSx matrix heterojunctions for proton/electron production, and the dark reaction on the defect-rich CuSx for CO2 reduction. The CuSx matrix could efficiently activate CO2 and stabilize the split hydrogen species to hinder undesired hydrogen evolution reaction, which benefits the proton-electron transfer to reduce CO2, a key step for bridging the two reaction systems.

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Tuning electrochemical transformation process of zeolitic imidazolate framework for efficient water oxidation activity Zhanwu Lei, Xu Jin, Jianming Li, Yang Liu, Jian Liu, Shuhong Jiao, Ruiguo Cao 2022, 65(2): 505-513.  DOI: 10.1016/j.jechem.2021.06.019 Abstract ( 8 )   PDF (4331KB) ( 2 )   Metal-organic frameworks (MOFs) have been widely studied as efficient electrocatalysts for water oxidation due to their tunable structure and easy preparation. However, the rational design of MOFs-based electrocatalysts and fundamental understanding of their structural evolution during oxygen evolution reaction (OER) remain critical challenges. Here, we report a facile approach to tune the structural transformation process of the Co-based zeolitic imidazolate framework (ZIF) during the OER process by using water molecules as a vacancy promoter. The modified ZIF catalyst accelerates the structural transformation from MOF precursor to electrochemical active species and simultaneously enhances the vacancy density during the electrochemical activation process. The optimized electrocatalyst exhibits an extremely low overpotential 175 mV to deliver 10 mA cm-2 and superior durability (100 h) at 100 mA cm-2. The comprehensive characterization results reveal the structural transformation from the initial tetrahedral Co sites to cobalt oxyhydroxide (CoOOH) and the formation process of oxygen vacancies (CoOOH-VO) at a high anodic potential. These findings represent a promising way to achieve highly active MOF-based electrocatalysts for water oxidation.

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In-situ structural evolution analysis of Zr-doped Na3V2(PO4)2F3 coated by N-doped carbon layer as high-performance cathode for sodium-ion batteries Chuan Guo, Jianwei Yang, Zhiyuan Cui, Shuo Qi, Qianqian Peng, Weiwei Sun, Li-Ping Lv, Yi Xu, Yong Wang, Shuangqiang Chen 2022, 65(2): 514-523.  DOI: 10.1016/j.jechem.2021.06.015 Abstract ( 8 )   PDF (8087KB) ( 7 )   With great superiorities in energy density, rate capability and structural stability, Na3V2(PO4)2F3 (NVPF) has attracted much attentions as cathode of sodium ion battery (SIB), but it also faces challenges on its poor intrinsic electronic conductivity and the controversial de/sodiation mechanism. Herein, a series of Zr-doped NVPF coated by N-doped carbon layer (~5 nm in thickness, homogenously) materials are fabricated by a sol-gel method, and the optimized heteroatom-doping amounts of Zr and N doping improve intrinsic properties on enlarging lattice distance and enhancing electronic conductivity, respectively. Specifically, among all samples of Na3V2-xZrx(PO4)2F3/NC (NVPF-Zr-x/NC, x = 0, 0.01, 0.02, 0.05, and 0.1), the optimized electrode of NVPF-Zr-0.02/NC delivers high reversible capacities (119.2 mAh g-1 at 0.5 C), superior rate capability (98.1 mA h g-1 at 20 C) and excellent cycling performance. The structural evolution of NVPF-Zr-0.02/NC electrode, in-situ monitored by X-ray diffractometer, follows a step-wise Na-extraction/intercalation mechanism with reversible multi-phase changes, not just a solid-solution-reaction one. Full cells of NVPF-Zr-0.02/NC//hard carbon demonstrate high capacity (99.8 mA h g-1 at 0.5 C), high out-put voltage (3.5 V) and good cycling stability. This work is favorable to accelerate the development of high-performance cathode materials and explore possible redox reaction mechanisms of SIBs

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Unveiling the origin of performance enhancement of photovoltaic devices by upconversion nanoparticles Huanhuan Yao, Guoqiang Peng, Zhizai Li, Ge Zhu, Wenquan Li, Zhipeng Ci, Wei Lan, Hao Jia, Bin Dong, Zhiwen Jin 2022, 65(2): 524-531.  DOI: 10.1016/j.jechem.2021.06.021 Abstract ( 9 )   PDF (3707KB) ( 2 )   To better utilize the infrared (IR) region in sunlight for photovoltaic devices (PVs), upconversion nanoparticles (UCNPs) have been proposed to improve power conversion efficiency (PCE). However, researchers recently have found that the upconversion (UC) effect is negligible in PVs performance improvement for their ultra-low UC photoluminescence quantum yields of UCNPs solid film, while the real mechanism of UCNPs in PVs has not been clearly studied. Herein, based on the material inorganic perovskites γ-CsPbI3, NaYF4:20%Yb3+,2%Er3+ UCNPs were integrated into different transport layer to optimize device performance. Compared with reference device, the short-circuit current density and PCE of optimized device reached 20.87 mA/cm2 (20.39 mA/cm2) and 18.34% (17.72%), respectively, without sacrificing open-circuit voltage and filling factor. Further experimental characterizations verified that the improved performance was attributable to enhanced visible light absorption instead of IR. To theoretically explain the statement, the light field distribution in device was simulated and the absorption in different layers was calculated. The results revealed that the introduction of UCNPs with different refractive index from other layers caused light field disturbance, and improved visible light captured by γ-CsPbI3. Importantly, through experiments and theoretical calculation, the research deeply explored the potential mechanism of UCNPs in optimizing PVs performance.

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The efficiency and toxicity of dodecafluoro-2-methylpentan-3-one in suppressing lithium-ion battery fire Yujun Liu, Kai Yang, Mingjie Zhang, Shi Li, Fei Gao, Qiangling Duan, Jinhua Sun, Qingsong Wang 2022, 65(2): 532-540.  DOI: 10.1016/j.jechem.2021.05.043 Abstract ( 18 )   PDF (3332KB) ( 7 )   Currently, the effective and clean suppression of lithium-ion battery (LIB) fires remains a challenge. The present work investigates the use of various inhibitor doses (Xin) of dodecafluoro-2-methylpentan-3-one (C6F12O) in 300 Ah LIBs, and systematically examines the thermal and toxic hazards of the extinguished batteries via real scale combustion and gas analysis. The inhibitor is shown to be completely effective. The inhibition mechanism involves a combination of chemical inhibition and physical cooling. While the chemical inhibition effect tends to saturate with increasing Xin, the physical cooling remains effective at higher inhibitor doses. However, extinguishing the battery fire with a high Xin of C6F12O is found to incur serious toxicity problems. These results are expected to provide a guideline for the design of inhibitor doses for the suppression of LIB fires.

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Microwave awakening the n-π* electronic transition in highly crystalline polymeric carbon nitride nanosheets for photocatalytic hydrogen generation Xiangang Lin, Haiwei Du, Daochuan Jiang, Peng Zhang, Zhiwu Yu, Hong Bi, Yupeng Yuan 2022, 65(2): 541-547.  DOI: 10.1016/j.jechem.2021.07.002 Abstract ( 3 )   PDF (3359KB) ( 2 )   The n-π* electronic transition in polymeric carbon nitride (PCN) can remarkably harvest visible light, which thus potentially promotes the photocatalytic hydrogen H2 generation. However, awaking the n-π* electronic transition has proven to be a grand challenge. Herein, we reported on the awakening of n-π* electronic transition by microwave thermolysis of urea pellet, which yielded the PCN with absorption edge of 600 nm, near 140 nm red-shift from 460 nm of pristine PCN. The n-π* electronic transition endows PCN with an increased photocatalytic H2 generation, with a highest H2 rate of 61.7 μmol h-1 under visible light exposure, which is near 6 times higher than that by using the PCN from the thermolysis of urea pellets in an electric furnace (10.6 μmol h-1). Furthermore, the n-π* transition in PCN leads to the longest wavelength of 535 nm that can initiate H2 generation, remarkably longer than the absorption edge of pristine PCN (460 nm). This work manifests the advantages of microwave sintering route to awaken the n-π* electronic transition in PCN for an increased photocatalytic performance.

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Insights into the efficient charge separation over Nb2O5/2D-C3N4 heterostructure for exceptional visible-light driven H2 evolution Jia Yan, Ting Wang, Siyao Qiu, Zhilong Song, Wangqin Zhu, Xianhu Liu, Jiabiao Lian, Chenghua Sun, Huaming Li 2022, 65(2): 548-555.  DOI: 10.1016/j.jechem.2021.06.030 Abstract ( 8 )   PDF (5443KB) ( 3 )   Two-dimensional carbon nitride (2D-C3N4) nanosheets are promising materials in photocatalytic water splitting, but still suffer from easy agglomeration and fast photogenerated electron-hole pairs recombination. To tackle this issue, herein, a hierarchical Nb2O5/2D-C3N4 heterostructure is precisely constructed and the built-in electric field between Nb2O5 and 2D-C3N4 can provide the driving force to separate/transfer the charge carriers efficiently. Moreover, the strongly Lewis acidic Nb2O5 can adsorb TEOA molecules on its surface at locally high concentrations to facilitate the oxidation reaction kinetics under irradiation, resulting in efficient photogenerated electrons-holes separation and exceptional photocatalytic hydrogen evolution. As expected, the champion Nb2O5/2D-C3N4 heterostructure achieves an exceptional H2 evolution rate of 31.6 mmol g-1 h-1, which is 213.6 times and 4.3 times higher than that of pristine Nb2O5 and 2D-C3N4, respectively. Moreover, the champion heterostructure possesses a high apparent quantum efficiency (AQE) of 45.08% at λ = 405 nm and superior cycling stability. Furthermore, a possible photocatalytic mechanism of the energy band alignment at the hetero-interface is proposed based on the systematical characterizations accompanied by density functional theory (DFT) calculations. This work paves the way for the precise construction of a high-quality heterostructured photocatalyst with efficient charge separation to boost hydrogen production.

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Killing two birds with one stone: Constructing tri-elements doped and hollow-structured carbon sphere by a single template for advanced potassium-ion hybrid capacitors Jiafeng Ruan, Yahui Zhao, Sainan Luo, Jiaming Hu, Yuepeng Pang, Fang Fang, Shiyou Zheng 2022, 65(2): 556-564.  DOI: 10.1016/j.jechem.2021.06.038 Abstract ( 3 )   PDF (11283KB) ( 1 )   Integrating the merits of long lifespan and excellent energy as well as power densities, potassium-ion hybrid capacitors (PIHCs) exhibit great prospects for future energy storage devices. To boost comprehensive performance of PIHCs, heteroatom-doping and morphology-tuning as two comprehensive strategies have been devoted to designing uniquely structural carbon-based materials with favorable advantages. An ideal strategy for simultaneous atomic doping and structural regulation is expected to be developed. Herein, we propose a novel “Killing Two Birds with One Stone” strategy to prepare a tri-elements doped hollow carbon sphere (TED-HCS) as PIHCs anodes, that is, a single template of spherical CoP particles is rationally adopted, which not only provides both a P source for heteroatom-doping but also acts as a self-sacrificial template for hollow-structure engineering. The multifunctional TED-HCS presents a high capacity of 473.0 mAh g-1 and excellent rate performance of 212.5 mAh g-1 at 5.0 A g-1. Remarkably, the as-assembled PIHCs show outstanding energy/power density (40.4 Wh kg-1/10500 W kg-1) and remain high-capacity retention of 89.15% even cycling 12,000 times. The “Killing Two Birds with One Stone” strategy offers new insight into the search for the preparation of carbon-based materials with multi-elements doping and specific morphology structure.

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Superfast and solvent-free core-shell assembly of sulfur/carbon active particles by hail-inspired nanostorm technology for high-energy-density Li-S batteries Lanxiang Feng, Zhiwei Zhu, Yan He, Yuan Ji, Xuewe He, Lei Jing, Mingbo Yang, Wei Yang, Yu Wang 2022, 65(2): 565-573.  DOI: 10.1016/j.jechem.2021.06.025 Abstract ( 5 )   PDF (5425KB) ( 3 )   The demand on low-carbon emission fabrication technologies for energy storage materials is increasing dramatically with the global interest on carbon neutrality. As a promising active material for metal-sulfur batteries, sulfur is of great interest due to its high-energy-density and abundance. However, there is a lack of industry-friendly and low-carbon fabrication strategies for high-performance sulfur-based active particles, which, however, is in critical need by their practical success. Herein, based on a hail-inspired sulfur nano-storm (HSN) technology developed in our lab, we report an energy-saving, solvent-free strategy for producing core-shell sulfur/carbon electrode particles (CNT@AC-S) in minutes. The fabrication of the CNT@AC-S electrode particles only involves low-cost sulfur blocks, commercial carbon nanotubes (CNT) and activated carbon (AC) micro-particles with high specific surface area. Based on the above core-shell CNT@AC-S particles, sulfur cathode with a high sulfur-loading of 9.2 mg cm-2 delivers a stable area capacity of 6.6 mAh cm-2 over 100 cycles. Furthermore, even for sulfur cathode with a super-high sulfur content (72 wt% over the whole electrode), it still delivers a high area capacity of 9 mAh cm-2 over 50 cycles in a quasi-lean electrolyte condition. In a nutshell, this study brings a green and industry-friendly fabrication strategy for cost-effective production of rationally designed S-rich electrode particles.

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Interface engineering of porous Fe2P-WO2.92 catalyst with oxygen vacancies for highly active and stable large-current oxygen evolution and overall water splitting Qimin Peng, Qiuting He, Yan Hu, Tayirjan Taylor Isimjan, Ruobing Hou, Xiulin Yang 2022, 65(2): 574-582.  DOI: 10.1016/j.jechem.2021.06.037 Abstract ( 8 )   PDF (4931KB) ( 2 )   Constructing a low cost, and high-efficiency oxygen evolution reaction (OER) electrocatalyst is of great significance for improving the performance of alkaline electrolyzer, which is still suffering from high-energy consumption. Herein, we created a porous iron phosphide and tungsten oxide self-supporting electrocatalyst with oxygen-containing vacancies on foam nickel (Fe2P-WO2.92/NF) through a facile in-situ growth, etching and phosphating strategies. The sequence-controllable strategy will not only generate oxygen vacancies and improve the charge transfer between Fe2P and WO2.92 components, but also improve the catalyst porosity and expose more active sites. Electrochemical studies illustrate that the Fe2P-WO2.92/NF catalyst presents good OER activity with a low overpotential of 267 mV at 100 mA cm-2, a small Tafel slope of 46.3 mV dec-1, high electrical conductivity, and reliable stability at high current density (100 mA cm-2 for over 60 h in 1.0 M KOH solution). Most significantly, the operating cell voltage of Fe2P-WO2.92/NF || Pt/C is as low as 1.90 V at 400 mA cm-2 in alkaline condition, which is one of the lowest reported in the literature. The electrocatalytic mechanism shows that the oxygen vacancies and the synergy between Fe2P and WO2.92 can adjust the electronic structure and provide more reaction sites, thereby synergistically increasing OER activity. This work provides a feasible strategy to fabricate high-efficiency and stable non-noble metal OER electrocatalysts on the engineering interface.

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Multi-dimensional hybrid flexible films promote uniform lithium deposition and mitigate volume change as lithium metal anodes Jian Yang, Tingting Feng, Junming Hou, Xinran Li, Boyu Chen, Cheng Chen, Zhi Chen, Yaochen Song, Mengqiang Wu 2022, 65(2): 583-591.  DOI: 10.1016/j.jechem.2021.07.001 Abstract ( 6 )   PDF (6440KB) ( 2 )   Lithium metal is the ultimate anode material for next-generation high-energy batteries. Yet, the practical application of lithium metal anodes is limited by the formation of Li dendrites and large volume changes. Herein, an effective multi-dimensional hybrid flexible film (MD-HFF) composed of iodine ion (0 dimension), CNTs (1 dimension) and graphene (2 dimensions) is designed for regulating Li deposition and mitigating volume changes. The multi-dimensional components serve separate roles: (1) iodine ion enhances the conductivity of the electrode and provides lithiophilic sites, (2) CNTs strengthen interlaminar conductance and mechanical strength, acting as a spring in the layered structure to alleviate volume changes during Li plating and stripping and (3) graphene provides mechanical flexibility and electrical conductivity. The resulting MD-HFF material supports stable Li plating/stripping and high Coulombic efficiency (99%) over 230 cycles at 1 mA cm-2 with a deposition capacity of 1 mAh cm-2. Theoretical calculations indicate that LiI contributes to the lateral growth of Li on the MD-HFF surface, thereby inhibiting the formation of Li dendrites. When paired with a typical NCM811 cathode, the assembled MD-HFF|| NCM811 cell exhibit improved capability and stable cycling performance. This research serves to guide material design in achieving Li anode materials that do not suffer from dendrite formation and volume changes.

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Benzotriazole derivative inhibits nonradiative recombination and improves the UV-stability of inverted MAPbI3 perovskite solar cells Xiaoyu Deng, Zhiyuan Cao, Chengbo Li, Shurong Wang, Feng Hao 2022, 65(2): 592-599.  DOI: 10.1016/j.jechem.2021.06.029 Abstract ( 5 )   PDF (3141KB) ( 4 )   Suppressing the nonradiative recombination in the bulk and surface of perovskite film is highly desired to improve the power conversion efficiency (PCE) and stability of halide perovskite solar cells (PSCs). In this study, a benzotriazole derivative (6-chloro-1-hydroxybenzotriazole, Cl-HOBT) is applied to improve the crystallinity and reduce the trap density of methylammonium lead iodide (MAPbI3) perovskite film. Meanwhile, incorporation of Cl-HOBT elongates the photoluminescence carrier lifetime and charge-recombination lifetime, implying the trap-assisted nonradiative recombination is greatly suppressed. Besides, the improved energy level alignment and enhanced built-in potential are conducive to the charge carrier separation and transfer process with Cl-HOBT. Consequently, a PCE of 20.27% and an open-circuit voltage (Voc) of 1.09 V are achieved for the inverted MAPbI3 PSCs, along with an 85% maintaining of the initial PCE under stored at relative humidity of 20% for 500 h. Furthermore, the existence of Cl-HOBT could inhibit the formation of Pb0 defect under prolonged UV illumination to retard the degradation of perovskite film. It is believed that this study paves a novel path for the realization of high-efficiency PSCs with UV-stability.

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Doped all-inorganic cesium zirconium halide perovskites with high-efficiency and tunable emission Pengfei Cheng, Daoyuan Zheng, Lu Feng, Yuefeng Liu, Junxue Liu, Juntao Li, Yang Yang, Guoxiong Wang, Keli Han 2022, 65(2): 600-604.  DOI: 10.1016/j.jechem.2021.06.033 Abstract ( 7 )   PDF (4694KB) ( 2 )   Doping enables manipulation of both the electrical and optical properties of halide perovskites. Herein, we incorporated Te4+ into Cs2ZrCl6 single crystal, simultaneously preserving the vacancy-ordered structure, to obtain an efficient yellow-emitting perovskite with a near-unity photoluminescence quantum yield (PLQY ≈ 97.6%). Te4+ doping modifies the hue and emission color of pristine Cs2ZrCl6, generates new absorption channels, and successfully extends the excitation energy from < 280 nm to 360-450 nm range. Detailed spectral characterizations, including ultrafast femtosecond transient absorption measurements, reveal that the bright yellow light is derived from triplet self-trapped excitons. Moreover, further tuning doping concentration enables Te-doped Cs2ZrCl6 single crystals to exhibit efficient warm white light emission. This work provides a new perspective for the development and design of stable lead-free perovskites with highly efficient luminescence.

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High-capacity Bi2O3 anode for 2.4 V neutral aqueous sodium-ion battery-supercapacitor hybrid device through phase conversion mechanism Mingze Xu, Yanli Niu, Xue Teng, Shuaiqi Gong, Lvlv Ji, Zuofeng Chen 2022, 65(2): 605-615.  DOI: 10.1016/j.jechem.2021.06.028 Abstract ( 8 )   PDF (14172KB) ( 4 )   Aqueous battery-supercapacitor hybrid devices (BSHs) are of great importance to enrich electrochemical energy storage systems with both high energy and power densities. However, further improvement of BSHs in aqueous electrolytes is greatly hampered by operating voltage and capacity limits. Different from the conventional intercalation/de-intercalation mechanism, Bi2O3 implements charge storage by a reversible phase conversion mechanism. Herein, taking Bi2O3 electrode with wide potential window (from -1.2 to 1 V vs. saturated calomel electrode) and high capacity as battery-type anode, we propose that the overall performance of aqueous BSHs can be greatly upgraded under neutral condition. By paring with stable layer-structured δ-MnO2 cathode, a sodium-ion Bi2O3//MnO2 BSH with an ultrahigh voltage of 2.4 V in neutral sodium sulfate electrolyte is developed for the first time. This hybrid device exhibits high capacity (~215 C g-1 at 1 mA cm-2), relatively long lifespan (~77.2% capacity retention after 1500 cycles), remarkable energy density (71.7 Wh kg-1@400.5 W kg-1) and power density (3204.3 W kg-1@18.8 Wh kg-1). Electrochemical measurements combining a set of spectroscopic techniques reveal the reversible phase conversion between bismuth oxide and metallic bismuth (Bi2O3 $\leftrightharpoons$Bi0) through Bi2+ transition phase in neutral sodium sulfate solution, which can deliver multielectron transfer up to 6, leading to the high-energy BSHs. Our work sheds light on the feasibility of using Bi2O3 electrode under neutral condition to address the issue of narrow voltage and low capacity for aqueous BSHs.

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A new flame-retardant polymer electrolyte with enhanced Li-ion conductivity for safe lithium-sulfur batteries Hongping Li, Yixi Kuai, Jun Yang, Shin-ichi Hirano, Yanna Nuli, Jiulin Wang 2022, 65(2): 616-622.  DOI: 10.1016/j.jechem.2021.06.036 Abstract ( 12 )   PDF (5874KB) ( 4 )   Flame-retardant polymer electrolytes (FRSPEs) are attractive due to their potential for fundamentally settling the safety issues of liquid electrolytes. However, the current FRSPEs have introduced large quantity of flame-retardant composition which cannot conduct lithium ions, thus decreasing the Li-ion conductivity. Here, we synthesize a novel liquid monomer 2-((bis((2-oxo-1,3-dioxolan-4-yl) methoxy) phosphoryl) oxy) ethyl acrylate (BDPA) for preparing FRSPE by in-situ polymerization, in which PBDPA polymer can not only conduct lithium ions, but also prevent burning. The prepared FRSPE demonstrated outstanding flame-retardant property, favorable lithium-ion conductivity of 5.65 × 10-4 S cm-1 at ambient temperature, and a wide electrochemical window up to 4.5 V. Moreover, the Li/in-situ FRSPE/S@pPAN cell exhibited favorable electrochemical performances. We believe that this work provides an effective strategy for establishing high-performance fireproof quasi-solid-state battery system.

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Synergistic effect of the metal-support interaction and interfacial oxygen vacancy for CO2 hydrogenation to methanol over Ni/In2O3 catalyst: A theoretical study Chenyang Shen, Qianqian Bao, Wenjuan Xue, Kaihang Sun, Zhitao Zhang, Xinyu Jia, Donghai Mei, Chang-jun Liu 2022, 65(2): 623-629.  DOI: 10.1016/j.jechem.2021.06.039 Abstract ( 2 )   PDF (4823KB) ( 2 )   Indium oxide supported nickel catalyst has been experimentally confirmed to be highly active for CO2 hydrogenation towards methanol. In this work, the reaction mechanism for CO2 hydrogenation to methanol has been investigated on a model Ni/In2O3 catalyst, i.e., Ni4/In2O3, via the density functional theory (DFT) study. Three possible reaction pathways, i.e., the formate pathway, CO hydrogenation and the reverse water-gas-shift (RWGS) pathways, have been examined on this model catalyst. It has been demonstrated that the RWGS pathway is the most theoretically-favored for CO2 hydrogenation to methanol. The complete RWGS pathway follows CO2 + 6H → COOH + 5H → CO + H2O + 4H → HCO + H2O + 3H → H2CO + H2O + 2H → H3CO + H2O + H → H3COH + H2O. Furthermore, it has been also proved that the interfacial oxygen vacancy can serve as the active site for boosting the CO2 adsorption and charge transfer between the nickel species and indium oxide, which synergistically promotes the consecutive CO2 hydrogenation towards methanol.

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Enhanced confinement synthesis of atomically dispersed Fe-N-C catalyst from resin polymer for oxygen reduction Ailing Song, Hao Tian, Wang Yang, Wu Yang, Yuhan Xie, Hao Liu, Guoxiu Wang, Guangjie Shao 2022, 65(2): 630-636.  DOI: 10.1016/j.jechem.2021.07.003 Abstract ( 7 )   PDF (6947KB) ( 2 )   Due to larger atom utilization, unique electronic properties and unsaturated coordination, atomically dispersed non-precious metal catalysts with outstanding performances have received great attention in electrocatalysis. Considering the challenge of serious aggregation, rational synthesis of an atomic catalyst with good dispersion of atoms is paramount to the development of these catalysts. Herein, we report an enhanced confinement strategy to synthesize a catalyst comprised of atomically dispersed Fe supported on porous nitrogen-doped graphitic carbon from the novel and more cross-linkable Melamine-Glyoxal Resin. Densified isolated grid trapping, excessive melamine restricting, and nitrogen anchoring are strongly combined to ensure the final atomic-level dispersion of metal atoms. Experimental studies revealed enhanced kinetics of the obtained catalyst towards oxygen reduction reaction (ORR). This catalytic activity originates from the highly active surface with atomically dispersed iron sites as well as the multi-level three-dimensional structure with fast mass and electron transfer. The enhanced confinement strategy endows the resin-derived atomic catalyst with a great prospect to develop for commercialization in future.

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Correlating the electronic structure of perovskite La1-xSrxCoO3 with activity for the oxygen evolution reaction: The critical role of Co 3d hole state Zechao Shen, Mei Qu, Jueli Shi, Freddy E. Oropeza, Victor A. de la Peña O’Shea, Giulio Gorni, C.M. Tian, Jan P. Hofmann, Jun Cheng, Jun Li, Kelvin H.L. Zhang 2022, 65(2): 637-645.  DOI: 10.1016/j.jechem.2021.06.032 Abstract ( 4 )   PDF (2754KB) ( 2 )   Perovskite LaCoO3 is being increasingly explored as an effective low-cost electrocatalyst for the oxygen evolution reaction (OER). Sr doping in LaCoO3 (La1-xSrxCoO3) has been found to substantially increase its catalytic activity. In this work, we report a detailed study on the evolution of the electronic structure of La1-xSrxCoO3 with 0 ≤ x ≤ 1 and its correlation with electrocatalytic activity for the OER. A combination of X-ray photoemission spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) was used to unravel the electronic density of states (DOS) near the Fermi level (EF), which provide insights into the key electronic structure features for the enhanced OER catalytic activity. Detailed analysis on the Co L-edge XAS suggest that LaCoO3 has a low spin state with t2g6eg0 configuration at room temperature. This implies that the high OER catalytic activity of LaCoO3 should not be rationalized by the occupancy of eg = 1 descriptor. Substituting Sr2+ for La3+ in LaCoO3 induces Co4+ oxidation states and effectively dopes hole states into the top of valence band. A semiconductor-to-metal transition is observed for × ≥ 0.2, due to the hole-induced electronic DOS at the EF and increased hybridization between Co 3d and O 2p. Such an electronic modulation enhances the surface adsorption of the *OH intermediate and reduces the energy barrier for interfacial charge transfer, thus improving the OER catalytic activity in La1-xSrxCoO3. In addition, we found that the La1-xSrxCoO3 surface undergoes amorphization after certain period of OER measurement, leading to a partial deactivation of the electrocatalyst. High Sr doping levels accelerated the amorphization process.

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CO2-adsorbent spongy electrode for non-aqueous Li-O2 batteries Yiseul Yoo, Giseung Lee, Min-Gi Jeong, Hun-Gi Jung, Sunghee Shin, Dongjin Byun, Taeeun Yim, Hee-Dae Lim 2022, 65(2): 646-653.  DOI: 10.1016/j.jechem.2021.06.022 Abstract ( 7 )   PDF (9431KB) ( 1 )   Regulation of the Li2CO3 byproduct is the most critical challenge in the field of non-aqueous Li-O2 batteries. Although considerable efforts have been devoted to preventing Li2CO3 formation, no approaches have suggested the ultimate solution of utilizing the clean Li2O2 reaction instead of that of Li2CO3. Even if extremely pure O2 is used in a Li-O2 cell, its complete elimination is impossible, eventually generating CO2 gas during charge. In this paper, we present the new concept of a CO2-adsorbent spongy electrode (CASE), which is designed to trap the evolved CO2 using adsorption materials. Various candidates composed of amine functional groups (-NH2) for capturing CO2 were screened, with quadrapurebenzylamine (QPBZA) exhibiting superior CO2-adsorbing ability among the proposed candidates. Accordingly, we fabricated the CASE by sandwiching QPBZA between porous carbon layers, which facilitated the transport of gaseous products. The new electrode was demonstrated to effectively capture the evolved CO2 during charge, therefore altering the reaction pathways to the ideal case. It is highly advantageous to mitigate the undesirable CO2 incorporation in the next discharge, resulting in improved cyclability. This novel concept of a CO2-sponging electrode provides an alternative route to the realization of practically meaningful Li-O2 batteries.

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Long-cycling lithium-oxygen batteries enabled by tailoring Li nucleation and deposition via lithiophilic oxygen vacancy in Vo-TiO2/Ti3C2Tx composite anodes Yu Yan, Chaozhu Shu, Ruixin Zheng, Minglu Li, Zhiqun Ran, Miao He, Longfei Ren, Dayue Du, Ying Zeng 2022, 65(2): 654-665.  DOI: 10.1016/j.jechem.2021.07.008 Abstract ( 6 )   PDF (14921KB) ( 1 )   Uncontrollable Li dendrite growth and infinite volume fluctuation during durative plating and stripping process gravely hinder the application of metallic Li electrode in lithium-oxygen batteries. Herein, oxygen vacancy-rich TiO2 (Vo-TiO2) nanoparticles (NPs) uniformly dispersing on Ti3C2Tx (Vo-TiO2/Ti3C2Tx) with excellent lithiophilicity feature are presented as effective composite anodes, on which a dense and uniform Li growth behavior is observed. Based on electrochemical studies, mutiphysics simulation and theoretical calculation, it is found that Vo-TiO2 coupling with three dimensional (3D) conductive Ti3C2Tx MXene forms highly ordered lithiophilic sites which succeed in guiding Li ions flux and adsorption, thus modulating the uniform Li nucleation and growth. As a result, this composite electrode is capable of preserving Li with high areal capacity of ~10 mAh cm-2 without the presence of dendrites and large volume expansion. Consequently, the as-prepared Vo-TiO2/Ti3C2Tx@Li anode shows outstanding performance including low voltage hysteresis (~19 mV) and superior durability (over 750 h). When assembling with the Vo-TiO2/Ti3C2Tx@Li anodes, lithium-oxygen batteries also deliver enhanced cycling stability and improved rate performance. This work demonstrates the effectiveness of oxygen vacancies in guiding Li nucleating and plating behavior at initial stage and brings a promising strategy for promoting the development of advanced Li metal-based batteries.

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Bottom-up lithium growth guided by Ag concentration gradient in 3D PVDF framework towards stable lithium metal anode Yulin Zhao, Liping Wang, Jian Zou, Qiwen Ran, Li Li, Pengyu Chen, Hailong Yu, Jian Gao, Xiaobin Niu 2022, 65(2): 666-673.  DOI: 10.1016/j.jechem.2021.06.027 Abstract ( 7 )   PDF (6518KB) ( 2 )   Three-dimensional (3D) frameworks have received much attention as an effective modification strategy for next-generation high-energy-density lithium metal batteries. However, the top-growth mode of lithium (Li) on the 3D framework remains a tough challenge. To achieve a uniform bottom-up Li growth, a scheme involving Ag concentration gradient in 3D PVDF framework (C-Ag/PVDF) is proposed. Ag nanoparticles with a concentration gradient induce an interface activity gradient in the 3D framework, and this gradient feature is still maintained during the cycle. As a result, the C-Ag/PVDF framework delivers a long lifespan over 1800 h at a current density of 1 mA cm-2 with a capacity of 1 mAh cm-2, and shows an ultra-long life (>1300 h) even at a high current density of 4 mA cm-2 with a capacity of 4 mAh cm-2. The advantage of concentration gradient provides further insights into the optimal design of the 3D framework for stable Li metal anode.

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Tailoring synergetic catalytic interface of VPO/Ni2P to boost hydrogen evolution under alkaline conditions Wenli Xu, Qiqi Li, Wenda Zhong, Bing Sun, Qiang Huang, Xu Nan, Yinhong Gao, Yao Yang, Qin Zhang, Nianjun Yang, Xuanke Li 2022, 65(2): 674-680.  DOI: 10.1016/j.jechem.2021.06.020 Abstract ( 5 )   PDF (6398KB) ( 2 )   Design of the catalyst for efficient water dissociation and hydrogen recombination is paramount in enhancement of the alkaline water electrolysis kinetics. Herein, we reported a delicate hierarchical (VO)2P2O7-Ni2P@NF (VPO-Ni2P@NF) hybrid catalyst that operated efficiently in alkaline media. The VPO and Ni2P respectively act as the water dissociation promoter and the hydrogen recombination center, which synergistically propel water adsorption/dissociation and H intermediates recombination. The resulting synergistic interfaces between VPO and Ni2P are verified to afford the catalyst an outstanding performance for hydrogen evolution reaction in alkaline media with an overpotential of 154 mV at 10 mA cm-2, Tafel slope of 65 mV dec-1, and remarkable durability. Furthermore, the catalyst presents the potential for overall water splitting. This work may shed fresh light on the high-performance electrocatalyst design and the application of VPO on water electrolysis.

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Grain size regulation for balancing cycle performance and rate capability of LiNi0.9Co0.055Mn0.045O2 single crystal nickel-rich cathode materials Jiapei Wang, Xibin Lu, Yingchao Zhang, Jiahui Zhou, Jiexi Wang, Shengming Xu 2022, 65(2): 681-687.  DOI: 10.1016/j.jechem.2021.06.017 Abstract ( 5 )   PDF (10564KB) ( 4 )   It is challenging to balance the cyclability and rate capability of single crystal nickel-rich cathode materials (Ni > 0.8). Multicomponent oxides by spray pyrolysis shows potential as highly-reactive precursors to synthesize single crystal nickel-rich cathode at lower temperature, yet Ni2+ will severely inhibit particle growth when Ni content exceeds 0.9. Herein, lithium nitrate (LiNO3) with low melting point and strong oxidation is introduced as collaborate lithium salts for fabrication of well-dispersed submicron and micron single crystal LiNi0.9Co0.055Mn0.045O2 (NCM90) cathode without extra unit operation. By changing amount of LiNO3, particle size regulation is realized and cation disorder can be diminished. The as-prepared material with optimal content of 4 wt% LiNO3 (NCM90-4LN) displays the most appropriate particle size (1 μm) with approximately stoichiometric structure, and presents better kinetics characterization of lithium-ion diffusion (15% higher than NCM90) and good electrochemical performance with specific discharge capacity of 220.6 and 173.8 mAh g-1 at 0.1C and 10C at room temperature, respectively. This work broadens the conventional research methodology of size regulation for single crystal Ni-rich cathode materials and is indispensable for the development of designing principal of nickel-rich cathode materials for lithium-ion batteries.