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2019, Vol. 34, No. 7　Online: 2019-07-15

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From bagasse lignin to efficient electrocatalyst: an economical and effective method (Pages 33-42)
Lignin is the second largest organic substance in the word. Therefore, different strategies and unremitting efforts have been adopted to explore its potential application as fuel and chemical raw materials. In this paper, we report a simple method to synthesize nitrogen and sulfur co-doped carbon nanosheets by using bagasse lignin. By adjusting the ratio of nitrogen source and annealing temperature, we obtained the ultrathin graphitic lignin carbon with abundant wrinkles with high surface area and large pore volume. The prepared bagasse ligninderived carbon material demonstrates competitive oxygen reduction reaction (ORR) activity, good methanol tolerance and superior stability compared to commercial Pt/C under alkaline and acidic electrolytes. This study develops an economical and effective method to prepare biocarbon catalyst for ORR in fuel cells.

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Construction of surface lattice oxygen in metallic N-CuCoS1.97 porous nanowire for wearable Zn-air battery Jie Yin, Binbin Wei, Yuxuan Li, Yefei Li, Pinxian Xi 2019, 28(7): 1-9.  DOI: 10.1016/j.jechem.2018.09.012 摘要 ( 18 )   Achieving high activity and stability oxygen evolution reaction (OER) catalysts to optimize the efficiency of metal-air battery, water splitting and other energy conversion devices, remains a formidable challenge. Herein, we demonstrate the metallic porous nanowires arrays with abundant defects via nitrogen and copper codoped CoS1.97 nanowires (N-CuCoS1.97 NWs). The N-CuCoS1.97 NWs can serve as an excellent OER self-supported electrode with an overpotential of 280 mV (j=10 mA cm-2) and remarkable long-term stability. The X-ray absorption near-edge structure (XANES) and X-ray photoelectron spectrum (XPS) measurements confirmed the surface lattice oxygen created on the N-CuCoS1.97 NWs during OER. Then, the density function theory (DFT) results evident that lattice oxygen constructed surface of N-CuCoS1.97 NWs has more favorable OER energetic profiles and absorption for reaction intermediate. More importantly, the flexible and wearable Zn-air battery fabricated by the N-CuCoS1.97 NWs shows excellent rechargeable and mechanical stability, which can be used in portable mobile device.

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Advanced electrosynthesis of hydrogen peroxide on oxidized carbon electrocatalyst Chang-Xin Zhao, Bo-Quan Li, Qiang Zhang 2019, 28(7): 10-11.  DOI: 10.1016/j.jechem.2018.09.002 摘要 ( 34 )

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Anti-solvent engineering for efficient semitransparent CH3NH3PbBr3 perovskite solar cells for greenhouse applications Waqas Siddique Subhani, Kai Wang, Minyong Du, Xiuli Wang, Ningyi Yuan, Jianning Ding, Shengzhong(Frank)Liu 2019, 28(7): 12-19.  DOI: 10.1016/j.jechem.2018.10.001 摘要 ( 24 )   With ideal combination of benefits that selectively converts high photon energy spectrum into electricity while transmitting low energy photons for photosynthesis, the CH3NH3PbBr3 perovskite solar cell (BPSC) is a promising candidate for efficient greenhouse based building integrated photovoltaic (BIPV) applications. However, the efficiency of BPSCs is still much lower than their theoretical efficiency. In general, interface band alignment is regarded as the vital factor of the BPSCs whereas only few reports on enhancing perovskite film quality. In this work, highly efficient BPSCs were fabricated by improving the crystallization process of CH3NH3PbBr3 with the assistance of anti-solvents. A new anti-solvent of diphenyl ether (DPE) was developed for its strong interaction with the solvents in the perovskite precursor solution. By using the anti-solvent of DPE, trap-state density of the CH3NH3PbBr3 film is reduced and the electron lifetime is enhanced along with the large-grain crystals compared with the samples from conventional anti-solvent of chlorobenzene. Upon preliminary optimization, the efficiencies of typical and semitransparent BPSCs are improved to as high as 9.54% and 7.51%, respectively. Optical absorption measurement demonstrates that the cell without metal electrode shows 80% transparency in the wavelength range of 550-1000 nm that is perfect for greenhouse vegetation. Considering that the cell absorbs light in the blue spectrum before 550 nm, it offers very high solar cell efficiency with only 17.8% of total photons, while over 60% of total photons can transmit through for photosynthesis if a transparent electrode can be obtained such as indium doped SnO2.

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Methane dehydroaromatization-A study on hydrogen use for catalyst reduction, role of molybdenum, the nature of catalyst support and significance of Bronsted acid sites Vaidheeshwar Ramasubramanian, Hema Ramsurn, Geoffrey L. Price 2019, 28(7): 20-32.  DOI: 10.1016/j.jechem.2018.09.018 摘要 ( 25 )   Methane dehydroaromatization was studied over Mo/SiO2 and Mo/HZSM-5 with different Mo loadings (2, 5, 10 wt%) at 973 K and 1023 K in a recirculating batch reactor. H2 pretreatment at 1023 K prior to methane activation has significantly improved the catalyst activity with increase in Mo loading and reduced the induction time on benzene formation in both Mo/SiO2 and Mo/HZSM-5. 10 wt% Mo/HZSM-5 gave a maximum methane conversion of 19% and~67% benzene selectivity at 1023 K. The XRD analysis of used catalysts revealed that the MoO3 species were converted to β-Mo2C phase. Studies on Mo/SiO2 catalysts showed that benzene was formed even in the absence of acidic zeolite sites. Reactions of ethylene in the presence of pure silica, HZSM-5 and in a blank reactor revealed that conversion of ethylene to aromatics was similar in case of the blank reactor and silica. Thus, it is believed that molybdenum carbide sites act as active sites only for C-H bond activation of methane and ethylene formation. Even though, ethylene can undergo subsequent oligomerization without any catalytic aid to form benzene at 973 K and above addition of acidic zeolites improved the selectivity of benzene.

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Preparation of nitrogen and sulfur co-doped ultrathin graphitic carbon via annealing bagasse lignin as potential electrocatalyst towards oxygen reduction reaction in alkaline and acid media Yixing Shen, Feng Peng, Yonghai Cao, Jianliang Zuo, Hongjuan Wang, Hao Yu 2019, 28(7): 33-42.  DOI: 10.1016/j.jechem.2018.09.021 摘要 ( 26 )   Renewable lignin used for synthesizing materials has been proven to be highly potential in specific electrochemistry. Here, we report a simple method to synthesize nitrogen and sulfur co-doped carbon nanosheets by using bagasse lignin, denoted as lignin-derived carbon (LC). By adjusting the ratio of nitrogen source and annealing temperature, we obtained the ultrathin graphitic lignin carbon (LC-4-1000) with abundant wrinkles with high surface area of 1208 m2g-1 and large pore volume of 1.40 cm3g-1. In alkaline medium, LC-4-1000 has more positive half-wave potential and nearly current density compared to commercial Pt/C for oxygen reduction reaction (ORR). More importantly, LC-4-1000 also exhibits comparable activity and superior stability for ORR in acid medium due to its high graphitic N ratio and a direct four electron pathway for ORR. This study develops a cost-effective and highly efficient method to prepare biocarbon catalyst for ORR in fuel cells.

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Strongly coupled N-doped carbon/Fe3O4/N-doped carbon hierarchical micro/nanostructures for enhanced lithium storage performance Tiantian Ma, Xianghong Liu, Li Sun, Yongshan Xu, Lingli Zheng, Jun Zhang 2019, 28(7): 43-51.  DOI: 10.1016/j.jechem.2018.09.017 摘要 ( 20 )   A strong interface coupling is of vital importance to develop metal oxide/carbon nanocomposite anodes for next-generation lithium ion batteries. Herein, a rational N-doped carbon riveting strategy is designed to boost the lithium storage performance of Fe3O4/N-doped carbon tubular structures. Polypyrrole (PPy) has been used as the precursor for N-doped carbon. N-doped carbon-riveted Fe3O4/N-doped carbon (N-C@Fe3O4@N-C) nanocomposites were obtained by pyrolysis of PPy-coated FeOOH@PPy nanotubes in Ar atmosphere. When tested as an anode for LIBs, the N-C@Fe3O4@N-C displays a high reversible discharge capacity of 675.8 mA h g-1 after 100 cycles at a current density of 100 mA g-1 and very good rate capability (470 mA h g-1 at 2 A g-1), which significantly surpasses the performance of Fe3O4@N-C. TEM analysis reveals that after battery cycling the FeOx particles detached from the carbon fibers for Fe3O4@N-C, while for N-C@Fe3O4@N-C the FeOx particles were still trapped in the carbon matrix, thus preserving good electrical contact. Consequently, the superior performance of N-C@Fe3O4@N-C is attributed to the synergistic effect between Fe3O4 and N-doped carbon combined with the unique structure properties of the nanocomposites. The strategy reported in this work is expected to be applicable for designing other electrode materials for LIBs.

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A bipolar verdazyl radical for a symmetric all-organic redox flow-type battery Grant D. Charlton, Stephanie M. Barbon, Joe B. Gilroy, C. Adam Dyker 2019, 28(7): 52-56.  DOI: 10.1016/j.jechem.2018.09.020 摘要 ( 44 )   A symmetric all-organic non-aqueous redox flow-type battery was investigated employing the neutral small molecule radical 3-phenyl-1,5-di-p-tolylverdazyl, which can be reversibly oxidized and reduced in one-electron processes, as the sole charge storage material. Cyclic voltammetry of the verdazyl radical in 0.5 M tetrabutylammonium hexafluorophosphate (TBAPF6) in acetonitrile revealed redox couples at-0.17 V and-1.15 V vs. Ag+/Ag, leading to a theoretical cell voltage of 0.98 V. From the dependence of peak currents on the square root of the scan rate, diffusion coefficients on the order of 4×10-6 cm2 s-1 were demonstrated. Cycling performance was assessed in a static cell employing a Tokoyuma AHA anion exchange membrane, with 0.04 M verdazyl as catholyte and anolyte in 0.5 M TBAPF6 in acetonitrile at a current density of 0.12 mA cm-2. Although coulombic efficiencies were good (94%-97%) throughout the experiment, the capacity faded gradually from high initial values of 93% of the theoretical discharge capacity to 35% by the 50th cycle. Voltage and energy efficiencies were 68% and 65%, respectively. Postcycling analysis by cyclic voltammetry revealed that decomposition of the active material with cycling is a leading cause of cell degradation.

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Ultrafine monolayer Co-containing layered double hydroxide nanosheets for water oxidation Xiaodan Jia, Xin Zhang, Jiaqing Zhao, Yufei Zhao, Yunxuan Zhao, Geoffrey I. N. Waterhouse, Run Shi, Li-Zhu Wu, Chen-Ho Tung, Tierui Zhang 2019, 28(7): 57-63.  DOI: 10.1016/j.jechem.2018.09.011 摘要 ( 38 )   For many two-dimensional (2D) materials, low coordination edges and corner sites offer greatly enhanced catalytic performance compared to basal sites, motivating the search for new synthetic approaches towards ultrathin and ultrafine 2D nanomaterials with high specific surface areas. To date, the synthesis of catalysts that are both ultrathin (monolayer) and ultrafine (lateral size <10 nm) has proven extremely challenging. Herein, using a facile ultrasonic exfoliation procedure, we describe the successful synthesis of ultrafine ZnCo-LDH nanosheets (denoted as ZnCo-UF) with a size~3.5 nm and thickness~0.5 nm. The single layer ZnCo-UF nanosheets possess an abundance of oxygen vacancies (VO) and unsaturated coordination sites, thereby affording outstanding electrocatalytic water oxidation performance. DFT calculations confirmed that VO on the surface of ZnCo-UF enhanced H2O adsorption via increasing the electropositivity of the nanosheets.

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Hierarchical sulfur and nitrogen co-doped carbon nanocages as efficient bifunctional oxygen electrocatalysts for rechargeable Zn-air battery Hao Fan, Yu Wang, Fujie Gao, Longqi Yang, Meng Liu, Xiao Du, Peng Wang, Lijun Yang, Qiang Wu, Xizhang Wang, Zheng Hu 2019, 28(7): 64-71.  DOI: 10.1016/j.jechem.2018.09.003 摘要 ( 29 )   Exploring inexpensive and efficient bifunctional electrocatalysts for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) is critical for rechargeable metal-air batteries. Herein, we report a new 3D hierarchical sulfur and nitrogen co-doped carbon nanocages (hSNCNC) as a promising bifunctional oxygen electrocatalyst by an in-situ MgO template method with pyridine and thiophene as the mixed precursor. The as-prepared hSNCNC exhibits a positive half-wave potential of 0.792 V (vs. reversible hydrogen electrode, RHE) for ORR, and a low operating potential of 1.640 V at a 10 mA cm-2 current density for OER. The reversible oxygen electrode index is 0.847 V, far superior to commercial Pt/C and IrO2, which reaches the top level of the reported bifunctional catalysts. Consequently, the hSNCNC as air cathodes in an assembled Zn-air battery features low charge/discharge overpotential and long lifetime. The remarkable properties arises from the introduced multiple heteroatom dopants and stable 3D hierarchical structure with multi-scale pores, which provides the abundant uniform high-active S and N species and efficient charge transfer as well as mass transportation. These results demonstrate the potential strategy in developing suitable carbon-based bi-/multi-functional catalysts to enable the next generation of the rechargeable metal-air batteries.

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Decorating cobalt phosphide and rhodium on reduced graphene oxide for high-efficiency hydrogen evolution reaction Haiyan Zheng, Xiubing Huang, Hongyi Gao, Wenjun Dong, Guilong Lu, Xiao Chen, Ge Wang 2019, 28(7): 72-79.  DOI: 10.1016/j.jechem.2018.10.009 摘要 ( 31 )   Electrochemical reduction of water to hydrogen holds great promise for clean energy, while its widespread application relies on the development of efficient catalysts with large surface area, abundant exposed active sites and superior electron conductivity. Herein, we report a facile strategy to configure an electrocatalyst composed of cobalt phosphide and rhodium uniformly anchored on reduced graphene oxide for hydrogen generation. The hybrids effectively integrate the exposed active sites, electron conductivity and synergistic effect of the catalyst. Electrochemical tests exhibit that the catalyst shows superior hydrogen evolution reaction catalytic activity and stability, with a small Tafel slope of 43 mV dec-1. Overpotentials as low as 29 and 72 mV are required to achieve current densities of 2 and 10 mA cm-2 in 0.5M H2SO4, respectively. The hybrid constitution with highly active sites on conductive substrate is a new strategy to synthesize extremely efficient electrocatalysts. Especially, the efficient synergistic effect among cobalt phosphide, rhodium and reduced graphene oxide provides a novel approach for configuring electrocatalysts with high electron efficiency.

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Highly efficient extraction of lithium from salt lake brine by LiAl-layered double hydroxides as lithium-ion-selective capturing material Ying Sun, Xiaoyu Guo, Shaofang Hu, Xu Xiang 2019, 28(7): 80-87.  DOI: 10.1016/j.jechem.2018.09.022 摘要 ( 35 )   The extraction of lithium from salt lake brine in the Chinese Qaidam Basin is challenging due to its high Mg/Li and Na/Li ratios. Herein, we utilized a reaction-coupled separation technology to separate sodium and lithium ions from a high Na/Li ratio brine (Na/Li=48.7, w/w) and extracted lithium with LiAl-layered double hydroxides (LiAl-LDHs). The LiAl-LDHs act as lithium-ion-selective capturing materials from multication brines. That is, the lithium ions selectively enter the solid phase to form LiAl-LDHs, and the sodium ions are still retained in the liquid phase. This is because the lithium ions can be incorporated into the structural vacancies of LiAl-LDHs, whereas the sodium ions cannot. The effects of reaction conditions on lithium loss and separation efficiency were investigated at both the nucleation and the crystallization stage, e.g., the nucleation rotating speed, the Li/Al molar ratio, the crystallization temperature and time, and co-existing cations. The lithium loss is as low as 3.93% under optimal separation conditions. The sodium ions remained in the solution. Consequently, an excellent Na/Li separation efficiency was achieved by this reaction-coupled separation technology. These findings confirm that LiAl-LDHs play a critical function in selectively capturing lithium ions from brines with a high Na/Li ratio, which is useful for the extraction of lithium ions from the abundant salt lake brine resources in China.

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Catalytic conversion of glucose to small polyols over a binary catalyst of vanadium modified beta zeolite and Ru/C Joby Sebastian, Mingyuan Zheng, Xinsheng Li, Jifeng Pang, Chan Wang, Tao Zhang 2019, 28(7): 88-95.  DOI: 10.1016/j.jechem.2018.10.003 摘要 ( 28 )   Catalytic conversion of glucose, the most abundant carbohydrate, to chemicals of petroleum origin has great desirability in terms of sustainability and industrial implementation. In this work, we attempted to exploit the vanadium-based catalysts with high retro-aldol condensation (RAC) activity for the synthesis of small polyols from glucose. Vanadium species incorporated or anchored beta zeolites were found to work effectively in synergy with 1Ru/AC to produce hydroxyacetone (HA) as the major product (34%) in a semi-continuously stirred tank reactor under 5% glucose concentration. Catalyst characterization by UV-vis and Raman spectral analysis revealed vanadium species mainly stayed in the incorporated form (tetrahedral) at 0.5% of loading and in the supported form (octahedral) at higher loadings up to 8%. Pyridine infrared spectra and temperature programmed desorption of NH3 revealed weak Lewis acid sites in dominance. Vanadium species in the catalysts displayed multiple catalytic roles (isomerization and RAC reaction, and synergism with the hydrogenation catalyst) in the synthesis of HA from glucose. Structureactivity correlation pointed out that the catalytic activity of vanadium species is not dependent on it coordination status, nevertheless, the adjacent vanadium atoms could possibly improve the isomerization rate over the RAC rate in favor of high yield of HA. The catalyst system is recyclable to at least five times without any considerable loss in its activity and structural integrity. The results presented here provide a promising route for the sustainable production of HA and polyols from carbohydrates by using a highly selective vanadium catalyst.

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Pt supported on Zn modified silicalite-1 zeolite as a catalyst for n-hexane aromatization Guodong Liu, Jiaxu Liu, Ning He, Shishan Sheng, Guiru Wang, Hongchen Guo 2019, 28(7): 96-103.  DOI: 10.1016/j.jechem.2018.09.009 摘要 ( 28 )   Platinum (Pt) supported on Zinc (Zn) modified silicalite-1 (S-1) zeolite (denoted as Pt-Zn/S-1) was prepared by using a wetness-impregnation method and applied in the n-hexane aromatization reaction for the first time. Both Lewis and Brønsted acid sites were detected in Pt-Zn/S-1 catalyst by means of FT-IR adsorption of NH3 experiment, which were identified as mostly weak and medium ones. Besides, Pt and Zn species showed strong interaction, as revealed by the TPR (Temperature-programmed reduction) and XPS (X-ray photoelectron spectroscopy) experiments. Pt-Zn/S-1 catalyst exhibited excellent aromatization function rather than isomerization and cracking side reactions in the conversion of n-hexane. Pulse experimental study showed that 75.6% of n-hexane conversion and 76.8% of benzene selectivity were obtained over Pt0.1-Zn6.0/S-1 catalyst at 550℃ and under atmospheric pressure. By spectroscopy tests and pulse experimental results, it was concluded that the n-hexane aromatization over Pt-Zn/S-1 catalyst follows a metal-acid bifunctional mechanism. Furthermore, with the assistance of Zn, the electron-deficient Pt species in Pt-Zn/S-1 showed good sulfur tolerance performance.

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Wet-spun poly(ionic liquid)-graphene hybrid fibers for high performance all-solid-state flexible supercapacitors Karthikeyan Gopalsamy, Qiuyan Yang, Shengying Cai, Tieqi Huang, Zhengguo Gao, Chao Gao 2019, 28(7): 104-110.  DOI: 10.1016/j.jechem.2018.10.007 摘要 ( 35 )   It is crucial to develop flexible and wearable electronic devices that have attracted tremendous interest due to their merits on compactness, flexibility and high capacitive properties. Herein we report the continuously ordered macroscopic poly(ionic liquid)-graphene fibers by wet spinning method via liquid crystal assembly for supercapacitor application. The fabricated all-solid-state supercapacitors exhibited a high areal capacitance (268.2 mF cm-2) and volumetric capacitance (204.6 F cm-3) with an outstanding areal energy density (9.31 μWh cm-2) and volumetric energy density (8.28 mWh cm-3). The fiber supercapacitors demonstrated exceptional cycle life for straight electrodes of about 10,000 cycles (94.2% capacitance retention) and flexibility at different angles (0°, 45°, 90°, 180°) along with a good flexible cycling stability after 6000 cycles (92.7% capacitance retention). To date, such a novel poly (ionic liquid)-graphene fiber supercapacitors would be a new platform in real-time flexible electronics.

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Recent progress on earth abundant electrocatalysts for hydrogen evolution reaction (HER) in alkaline medium to achieve efficient water splitting-A review Jamesh Mohammed-Ibrahim, Xiaoming Sun 2019, 28(7): 111-160.  DOI: 10.1016/j.jechem.2018.09.016 摘要 ( 216 )   Developing earth-abundant-electrocatalysts for hydrogen evolution reaction is one of the promising ways to achieve efficient water-splitting for hydrogen production (a clean chemical fuel). This paper reviews the activity, stability and durability for hydrogen evolution reaction in alkaline medium of different types of recently reported potential electrocatalysts such as Ni, Co, NiCo, Fe, Cu, W, Mo, Se, Mn, Zn, V, and metal free based earth-abundant-electrocatalysts. Further, this paper reviews the strategies used to achieve the remarkably low overpotential (including η10: ≤ 35 mV), high long term stability (including ≥ 100 h) and high durability (including ≥ 5000 cycles) of potential earth-abundant-electrocatalysts for hydrogen evolution reaction in alkaline medium and those are better or well comparable with the state-of-the-art, noble, Pt/C electrocatalyst. Finally, this paper summarizes the efficient strategies such as preparing porous structured materials, preparing nanostructured materials with superaerophobic surface, preparing nanostructured materials, preparing carbon composites/integrating electrocatalysts with carbon, preparing amorphous materials, preparing materials with oxygen vacancies/defects, preparing metal chalcogenides, preparing bimetallic/multi-metallic materials, doping metals or heteroatoms, preparing electrocatalysts with core-shell structure, decorating electrocatalysts with amines, preparing homojunction/heterojunction structured materials, preparing hollow structured materials, and preparing boronrich surface to enhance the activity, stability, and durability for HER.

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Electrocatalytic water splitting at nitrogen-doped carbon layers-encapsulated nickel cobalt selenide Chuanlai Jiao, Xiangjie Bo, Ming Zhou 2019, 28(7): 161-170.  DOI: 10.1016/j.jechem.2018.09.015 摘要 ( 35 )   Generally, the catalytic overpotentials of hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) are unavoidable because of the low charge transfer. In this work, two strategies of alloying of Co with Ni and enclosing of electrocatalysts with carbonaceous materials were both used to accelerate the catalytic efficiency of cobalt selenide for water splitting. The nitrogen-doped carbon (NC) layer improves the reaction kinetics by efficient charge transfer. The alloying of metal into composited electrocatalysts can modify the electronic properties of host materials, thereby tuning the adsorption behavior of intermediate and improving the electrocatalytic activity. As expected, Nyquist plots reveal that the charge-transfer resistance (Rct) of nickel cobalt selenide encapsulated into nitrogen-doped carbon layer (CoNiSe/NC-3, Co:Ni=1:1) are just 5 and 9Ω for HER and OER, respectively, which are much lower than those of CoSe/NC-1 (Co:Ni=1:0) (81 and 138Ω) and CoNiSe/NC-3 without NC (CoNiSe-3) (54 and 25Ω). With the high charge transfer and porous structure, CoNiSe/NC-3 shows good performance for both HER and OER. When current density reaches 10 mA cm-2, only 100 and 270 mV overpotentials are required for HER and OER, respectively. With the potential of 1.65 V, full water splitting also can be catalyzed by CoNiSe/NC-3 with current density of 20 mA cm-2, suggesting that CoNiSe/NC-3 could be used as replacement for noble metal electrocatalysts.

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Biomass-derived porous carbon materials for advanced lithium sulfur batteries Poting Liu, Yunyi Wang, Jiehua Liu 2019, 28(7): 171-185.  DOI: 10.1016/j.jechem.2018.10.005 摘要 ( 46 )   Biomass, as the most widely used carbon sources, is the main ingredient in the formation of fossil fuels. Biomass-derived novel carbons (BDNCs) have attracted much attention because of its adjustable physical/chemical properties, environmentally friendliness, and considerable economic value. Nature contributes to the biomass with bizarre microstructures with micropores, mesopores or hierarchical pores. Currently, it has been confirmed that biomass has great potential applications in energy storage devices, especially in lithium-sulfur (Li-S) batteries. In this article, the synthesis and function of BDNCs for Li-S batteries are presented, and the electrochemical effects of structural diversity, porosity and surface heteroatom doping of the carbons in Li-S batteries are discussed. In addition, the economic benefits, new trends and challenges are also proposed for further design excellent BDNCs for Li-S batteries.

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Asphaltenes: Separations, structural analysis and applications Pingping Zuo, Shijie Qu, Wenzhong Shen 2019, 28(7): 186-207.  DOI: 10.1016/j.jechem.2018.10.004 摘要 ( 36 )   Asphaltenes, complex aromatic compounds from various carbonaceous sources, could be obtained by solvent dissolution, filtration and adsorption. It was difficult to clarify the molecular structures and chemical properties of asphaltene due to its structural similarity, composition complexity and source dependences. Many techniques, like Mass spectrometry, Chromatography, Nuclear magnetic resonance spectroscopy, Infrared spectroscopy, Roman spectroscopy, Fluorescence spectroscopy, X-ray diffraction analysis and Small-angle scattering techniques and so on, have revealed some valuable descriptions of asphaltenes chemical compositions and fundamental structures. Moreover, advanced Mass spectrometry, Atomic force microscopy and Scanning tunneling microscopy could provide more clear and essential molecular compounds and structures in asphaltenes. In addition, several asphaltenes models have succeeded to illustrate aggregation properties asphaltene. In this work, the progress on asphaltene separation, characterization and application was summarized, and the similarities and differences between coal-derived asphaltenes and petroleum asphaltenes were compared. Furthermore, the reactivity of asphaltenes has been discussed in the aspect of hydroprocessing, pyrolysis and gasification. Asphaltene was excellent carbon precursor for functional carbon material due to its high aromaticity and carbon yield; several porous carbon nanosheets from asphaltenes that would be prospective electrode materials after being graphitized were shown. Pitch-based carbon fiber derived from coal-derived asphaltenes displayed a tensile strength of 1.0 GPa and elastic modulus of 350 MPa, respectively. These powerful advances will provide asphaltenes promising developments.

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Enhanced capacity to CO2 sorption in humid conditions with a K-doped biocarbon Nausika Querejet, Fernando Rubier, Covadonga Pevid 2019, 28(7): 208-219.  DOI: 10.1016/j.jechem.2018.09.023 摘要 ( 26 )   Solid sorbents with enhanced capacity and selectivity towards CO2 are crucial in the design of an efficient capture process. Among the possible alternatives, K2CO3-doped activated carbons have shown high CO2 capture capacity and rapid carbonation reaction rate. In this work, a sustainable and low-cost approach is developed with a biomass-based activated carbon or biocarbon as support. The CO2 capture performance in cyclic sorption-desorption operation and the sorption kinetics have been investigated under different scenarios in a purpose-built fixed-bed set-up. Independent of the H2O concentration in the flue gas, a constant relative humidity (~20%) in the K2CO3-doped biocarbon bed promoted the carbonation reaction and boosted the CO2 sorption capacity (1.92 mmol/g at 50℃ and 14 kPa partial pressure of CO2). Carbonation is slower than physical adsorption of CO2 but wise process design could tune the operation conditions and balance capture capacity and sorption kinetics.

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N/S co-doped 3D carbon framework prepared by a facile morphology-controlled solid-state pyrolysis method for oxygen reduction reaction in both acidic and alkaline media Juan Nong, Min Zhu, Kun He, Aosheng Zhu, Pu Xie, Minzhi Rong, Mingqiu Zhang 2019, 28(7): 220-226.  DOI: 10.1016/j.jechem.2018.10.006 摘要 ( 26 )   Developing high-performance non-precious metal electrocatalysts for oxygen reduction reaction (ORR) is crucial for the commercialization of fuel cells and metal-air batteries. However, doped carbon-based materials only show good ORR activity in alkaline medium, and become less effective in acidic environment. We believe that an appropriate combination of both ionic and electronic transport path, and well dopant distribution of doped carbon-based materials would help to realize high ORR performance under both acidic and alkaline conditions. Accordingly, a nitrogen and sulfur co-doped carbon framework with hierarchical through-hole structure is fabricated by morphology-controlled solid-state pyrolysis of poly(aniline-co-2-aminothiophenol) foam. The uniform high concentrations of nitrogen and sulfur, high intrinsic conductivity, and integrated three dimensional ionic and electronic transfer passageways of the 3D porous structure lead to synergistic effects in catalyzing ORR. As a result, the limiting current density of the carbonized poly(aniline-co-2-aminothiophenol) foam is equivalent to commercial Pt/C in acidic environment, and twice the latter in alkaline medium.

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Supporting IrO2 and IrRuOx nanoparticles on TiO2 and Nb-doped TiO2 nanotubes as electrocatalysts for the oxygen evolution reaction Radostina V. Genova-Koleva, Francisco Alcaide, Garbiñe Álvarez, Pere L. Cabot, Hans-Jürgen Grande, María V. Martínez-Huerta, Oscar Miguel 2019, 28(7): 227-239.  DOI: 10.1016/j.jechem.2019.03.008 摘要 ( 21 )   IrO2 and IrRuOx (Ir:Ru 60:40 at%), supported by 50 wt% onto titania nanotubes (TNTs) and (3 at% Nb) Nb-doped titania nanotubes (Nb-TNTs), as electrocatalysts for the oxygen evolution reaction (OER), were synthesized and characterized by means of structural, surface analytical and electrochemical techniques. Nb doping of titania significantly increased the surface area of the support from 145 (TNTs) to 260 m2 g-1 (Nb-TNTs), which was significantly higher than those of the Nb-doped titania supports previously reported in the literature. The surface analytical techniques showed good dispersion of the catalysts onto the supports. The X-ray photoelectron spectroscopy analyses showed that Nb was mainly in the form of Nb(IV) species, the suitable form to behave as a donor introducing free electrons to the conduction band of titania. The redox transitions of the cyclic voltammograms, in agreement with the XPS results, were found to be reversible. Despite the supported materials presented bigger crystallite sizes than the unsupported ones, the total number of active sites of the former was also higher due to their better catalyst dispersion. Considering the outer and the total charges of the cyclic voltammograms in the range 0.1-1.4 V, stability and electrode potentials at given current densities, the preferred catalyst was IrO2 supported on the Nb-TNTs. The electrode potentials corresponding to given current densities were between the smallest ones given in the literature despite the small oxide loading used in this work and its Nb doping, thus making the Nb-TNTs-supported IrO2 catalyst a promising candidate for the OER. The good dispersion of IrO2, high specific surface area of the Nb-doped supports, accessibility of the electroactive centers, increased stability due to Nb doping and electron donor properties of the Nb(IV) oxide species were considered the main reasons for its good performance.

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A new mutually destabilized reactive hydride system: LiBH4-Mg2NiH4 Nils Bergemann, Claudio Pistidda, Maike Uptmoor, Chiara Milanese, Antonio Santoru, Thomas Emmler, Julián Puszkiel, Martin Dornheim, Thomas Klassen 2019, 28(7): 240-254.  DOI: 10.1016/j.jechem.2019.03.011 摘要 ( 23 )   In this work, the hydrogen sorption properties of the LiBH4-Mg2NiH4 composite system with the molar ratio 2:2.5 were thoroughly investigated as a function of the applied temperature and hydrogen pressure. To the best of our knowledge, it has been possible to prove experimentally the mutual destabilization between LiBH4 and Mg2NiH4. A detailed account of the kinetic and thermodynamic features of the dehydrogenation process is reported here.