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Yang Liu, Feng Li, Haidong Yang, Jing Li, Ping Ma, Yan Zhu, Jiantai Ma
There is a vital need to explore highly-efficient and stable nonprecious-metal catalysts for oxygen evolution reaction (OER) to reduce the overpotential and further improve the energy conversion efficiency. Herein, we report a unique and cost-effective lyophilized and thermal two step procedure to synthesize high-performance CoFe alloy nanoparticles embedded in N-doped carbon nanosheets interspersed with carbon nanotubes (CoFe-N-CN/CNTs) hybrid. The lyophilization step during catalysts preparation is beneficial to uniform the dispersion of carbon-like precursors and avoid the agglomeration of metal particles...
May 22, 2018: ChemSusChem
Zamyla Morgan Chan, Daniil A Kitchaev, Johanna Nelson Weker, Christoph Schnedermann, Kipil Lim, Gerbrand Ceder, William Tumas, Michael F Toney, Daniel G Nocera
Electrodeposited manganese oxide films are promising catalysts for promoting the oxygen evolution reaction (OER), especially in acidic solutions. The activity of these catalysts is known to be enhanced by the introduction of Mn3+ We present in situ electrochemical and X-ray absorption spectroscopic studies, which reveal that Mn3+ may be introduced into MnO2 by an electrochemically induced comproportionation reaction with Mn2+ and that Mn3+ persists in OER active films. Extended X-ray absorption fine structure (EXAFS) spectra of the Mn3+ -activated films indicate a decrease in the Mn-O coordination number, and Raman microspectroscopy reveals the presence of distorted Mn-O environments...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
Hai Xiao, Hyeyoung Shin, William A Goddard
The oxygen evolution reaction (OER) is critical to solar production of fuels, but the reaction mechanism underlying the performance for a best OER catalyst, Fe-doped NiOOH [(Ni,Fe)OOH], remains highly controversial. We used grand canonical quantum mechanics to predict the OER mechanisms including kinetics and thus overpotentials as a function of Fe content in (Ni,Fe)OOH catalysts. We find that density functional theory (DFT) without exact exchange predicts that addition of Fe does not reduce the overpotential much...
May 21, 2018: Proceedings of the National Academy of Sciences of the United States of America
Yujie Han, You Yu, Lingling Zhang, Liang Huang, Junfeng Zhai, Shaojun Dong
The transition metal oxides based catalysts have drawn great attention for their application in the electrolysis of water for renewable energy generation. Although manganese oxides were rarely used as oxygen evolution reaction (OER) catalysts, they were still considered as active and efficient OER catalysts due to the earth-abundant and low toxic nature of manganese. In this work, we proposed a facile method for the synthesis of high-performance electrochemical OER catalyst by magnetically stirring the mixture of 1,3,4-thiadiazole-2,5-dithiol (DMTD), Ni2+ and MnO2 nanowires (NWs) in ethanol at room temperature, noted as Ni/DMTD/MnO2 ...
August 15, 2018: Talanta
Tanyuan Wang, Gyutae Nam, Yue Jin, Xingyu Wang, Pengju Ren, Min Gyu Kim, Jiashun Liang, Xiaodong Wen, Haeseong Jang, Jiantao Han, Yunhui Huang, Qing Li, Jaephil Cho
A facile H2 O2 oxidation treatment to tune the properties of metal disulfides for oxygen evolution reaction (OER) activity enhancement is introduced. With this method, the degree of oxidation can be readily controlled and the effect of surface S residues in the resulted metal (oxy)hydroxides for the OER is revealed for the first time. The developed NiFe (oxy)hydroxide catalyst with residual S demonstrates an extraordinarily low OER overpotential of 190 mV at the current density of 10 mA cm-2 after coupling with carbon nanotubes, and outstanding performance in Zn-air battery tests...
May 21, 2018: Advanced Materials
P Lettenmeier, J Majchel, L Wang, V A Saveleva, S Zafeiratos, E R Savinova, J-J Gallet, F Bournel, A S Gago, K A Friedrich
A stable and cost effective oxygen evolution reaction (OER) catalyst is crucial for the large-scale market penetration of proton exchange membrane (PEM) water electrolyzers. We show that the synthesis of iridium nanoparticles in either low purity ethanol or water, or in the absence of a surfactant, is detrimental to the electrocatalytic properties of the materials. Adding NaBH4 in excess improves the purity of the catalyst enhancing the OER activity up to 100 A gIr -1 at 1.51 V vs. RHE, the highest value reported so far for high purity Ir nanoparticles...
April 14, 2018: Chemical Science
Junyuan Xu, Junjie Li, Dehua Xiong, Bingsen Zhang, Yuefeng Liu, Kuang-Hsu Wu, Isilda Amorim, Wei Li, Lifeng Liu
Transition metal phosphides (TMPs) have recently emerged as a new class of pre-catalysts that can efficiently catalyze the oxygen evolution reaction (OER). However, how the OER activity of TMPs varies with the catalyst composition has not been systematically explored. Here, we report the alkaline OER electrolysis of a series of nanoparticulate phosphides containing different equimolar metal (M = Fe, Co, Ni) components. Notable trends in OER activity are observed, following the order of FeP < NiP < CoP < FeNiP < FeCoP < CoNiP < FeCoNiP, which indicate that the introduction of a secondary metal(s) to a mono-metallic TMP substantially boosts the OER performance...
April 14, 2018: Chemical Science
Viktoriia A Saveleva, Li Wang, Detre Teschner, Travis E Jones, Aldo S Gago, K Andreas Friedrich, Spyridon Zafeiratos, Robert Schloegl, Elena R Savinova
Progress in the development of the proton exchange membrane (PEM) water electrolysis technology requires decreasing the anode overpotential, where the sluggish multistep oxygen evolution reaction (OER) occurs. This calls for the understanding of the nature of the active OER sites and reaction intermediates, which are still being debated. In this work, we apply synchrotron radiation - based near ambient pressure X-ray photoelectron and absorption spectroscopies under operando conditions in order to unveil the nature of the reaction intermediates and shed light on the OER mechanism on electrocatalysts most widely used in PEM electrolyzers - electrochemical and thermal iridium oxides...
May 18, 2018: Journal of Physical Chemistry Letters
Shuangyin Wang, Dawei Chen, Man Qiao, Yingrui Lu, L I Hao, Dongdong Liu, Chungli Dong, Yafei Li
Oxygen evolution reaction (OER) is an ideal model to study the relationship between the activity and the surface properties of catalysts. Defect engineering has been extensively developed to tune the electrocatalytic activity for OER. Compared to the anion vacancies in metal oxides, cation vacancies are more challenging to selectively generate, and the insight into the structure and activity of cation vacancies-rich catalysts are lacked. Herein, using SnCoFe perovskite hydroxide as precursors, we have preferentially produced abundant Sn vacancies on the surface by Ar plasma...
May 17, 2018: Angewandte Chemie
Sicong Wang, Zhenyuan Teng, Chengyin Wang, Guoxiu Wang
High activity and stability are crucial for practical electrocatalysts used for reactions in fuel cells, metal-air batteries and water electrolysis including ORR, HER, OER and oxidation reactions of formic acid and alcohols. N-C based electrocatalysts have shown promising prospects for catalyzing these reactions, however, there is no systematic review for strategies toward engineering active and stable N-C based electrocatalysts reported by far. Herein, a comprehensive comparison of recently reported N-C based electrocatalysts regarding both electrocatalytic activity and long-term stability is presented...
May 17, 2018: ChemSusChem
Guodong Shi, Cong Yu, Zixiong Fan, Junbo Li, Mingjian Yuan
Graphdiyne (GDY), a novel two-dimensional full-carbon material, has attracted lots of attention because of its high conjugated system comprising sp2 and sp-hybridized carbons. The distinctive structure characteristics endow it unique electronic structure, uniform distributed pores and excellent chemical stability. A novel GDY-supported NiFe layered double hydroxide (LDH) composite was successfully prepared for the first time. By taking advantage of the increased surface active areas and improved conductivity, the designed hierarchical GDY@NiFe composite exhibits outstanding catalytic activity that only required a small overpotential about 260 mV to achieve the current density of 10 mA cm-2 ...
May 16, 2018: ACS Applied Materials & Interfaces
Yanzhou Wang, Panpan Gao, Xiaoxu Wang, Jinrong Huo, Lu Li, Yajing Zhang, Alex A Volinsky, Ping Qian, Yanjing Su
The pursuit of catalysts to promote effective water oxidization to produce oxygen has become a research subject of high priority for water splitting. Here, first-principles calculations are employed to study the water-splitting oxygen evolution reaction (OER) on ∼1.5 nm diameter Au13@Ni120P50 core-shell nanoclusters. Water splitting to produce oxygen proceeds in four intermediate reaction steps (OH*, O*, OOH* and O2). Adsorption configurations and adsorption energies for the species involved in OER on both Au13@Ni120P50 cluster and Ni12P5(001) supported by Au are presented...
May 16, 2018: Physical Chemistry Chemical Physics: PCCP
Dandan Zhao, Yecan Pi, Qi Shao, Yonggang Feng, Ying Zhang, Xiaoqing Huang
The development of electrocatalysts with high activity and stability for oxygen evolution reaction (OER) is critically important, the one being regarded as the bottleneck process of overall water splitting. Herein, we fulfill significant OER improvement in both activity and stability by constructing a class of Ni(OH)2 -CeO2 supported on carbon paper (Ni x Ce y @CP) with an intimate hydroxide (Ni(OH)2 )-oxide (CeO2 ) interface. Such interface largely promotes the OER activity with a low overpotential of 220 mV at 10 mA cm-2 and a small Tafel slope of 81...
May 17, 2018: ACS Nano
Bo You, Guanqun Han, Yujie Sun
Renewable energy-driven hydrogen production from electrocatalytic and photocatalytic water splitting has been widely recognized as a promising approach to utilize green energy resources and hence reduces our dependence on legacy fossil fuels as well as alleviates net carbon dioxide emissions. The realization of large-scale water splitting, however, is mainly impeded by its slow kinetics, particularly because of its sluggish anodic half reaction, the oxygen evolution reaction (OER), whose product O2 is ironically not of high value...
May 15, 2018: Chemical Communications: Chem Comm
Wei-Liang Li, Tzung-Wen Chiou, Chien-Hong Chen, Yi-Ju Yu, Li-Kang Chu, Wen-Feng Liaw
In artificial photosynthesis, water splitting plays an important role for the conversion and storage of renewable energy sources. Here, we report a study on the electrocatalytic properties of the electrodeposited-film electrodes derived from irreversible electro-reduction/-oxidation of a molecular dinitrosyl iron complex (DNIC) {Fe(NO)2}9 [(Me6tren)Fe(NO)2]+ (Me6tren = tris[2-(dimethylamino)ethyl]amine) for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER) in alkaline solution, individually...
May 14, 2018: Dalton Transactions: An International Journal of Inorganic Chemistry
Yang Yang, Li Cheng Kao, Yuanyue Liu, Ke Sun, Hongtao Yu, Jinghua Guo, Sofia Ya Hsuan Liou, Michael R Hoffmann
TiO2 has long been recognized as a stable and reusable photocatalyst for water splitting and pollution control. However, it is an inefficient anode material in the absence of photoactivation due to its low electron conductivity. To overcome this limitation, a series of conductive TiO2 nanotube array electrodes have been developed. Even though nanotube arrays are effective for electrochemical oxidation initially, deactivation is often observed within a few hours. To overcome the problem of deactivation, we have synthesized cobalt-doped Black-TiO2 nanotube array (Co-Black NTA) electrodes that are stable for more than 200 h of continuous operation in a NaClO4 electrolyte at 10 mA cm-2 ...
May 4, 2018: ACS Catalysis
Jinxiu Zhao, Xianghong Li, Guanwei Cui, Xuping Sun
Alkaline water splitting offers a simple method for the mass production of hydrogen but suffers from the sluggish kinetics of the anodic oxygen evolution reaction (OER). Here, we report on the development of an Fe-doped NiCr2O4 nanoparticle film on Ni foam (Fe-NiCr2O4/NF) as a non-noble-metal OER electrocatalyst with superior catalytic activity at alkaline pH. Such Fe-NiCr2O4/NF demands overpotentials as low as 228 and 318 mV to drive current densities of 20 and 500 mA cm-2, respectively, in 1.0 M KOH. Notably, it also shows strong long-term electrochemical durability with its activity being retained for at least 60 h...
May 11, 2018: Chemical Communications: Chem Comm
Hyeyoung Shin, Hai Xiao, William A Goddard
The oxygen evolution reaction (OER) is critical to efficient water splitting to produce the H2 fuel for sustainable energy production. Currently, the best non-noble metal OER electrocatalyst in base conditions is the Fe-doped NiOOH (Ni1-xFexOOH), with η=0.4, but much lower values are desired. We use density functional theory to determine the overall mechanism for the OER of Ni1-xFexOOH, concluding that promoting radical character on the metal-oxo bond is critical to efficient OER. Then we consider replacing Fe with 17 other transition metals of the Fe, Ru, and Os rows, where we find 3 new promising candidates: Co, Rh, and Ir, which we predict to have η=0...
May 11, 2018: Journal of the American Chemical Society
Hainan Sun, Gao Chen, Jaka Sunarso, Jie Dai, Wei Zhou, Zongping Shao
Abundant, highly active, and durable oxygen evolution reaction (OER) electrocatalyst is an enabling component for a more sustainable energy future. We report, herein, a molybdenum and niobium co-doped B-site ordered double perovskite oxide with a compositional formula of Ba2CoMo0.5Nb0.5O6- (BCMN) as an active and robust catalyst for OER in an alkaline electrolyte. BCMN displayed a low overpotential of 445 mA at a current density of 10 mA cm-2disk. BCMN also showed long-term stability in alkaline medium. This work hints towards the possibility to combine co-doping approach with double perovskite structure formation to achieve significant enhancement on the OER performance...
May 9, 2018: ACS Applied Materials & Interfaces
Wenming Zhang, Xiuyun Yao, Shengnan Zhou, Xiaowei Li, Ling Li, Ze Yu, Lin Gu
Herein, an approach is reported for fabrication of Co-Nx -embedded 1D porous carbon nanofibers (CNFs) with graphitic carbon-encased Co nanoparticles originated from metal-organic frameworks (MOFs), which is further explored as a bifunctional electrocatalyst for both oxygen reduction reaction (ORR) and oxygen evolution reaction (OER). Electrochemical results reveal that the electrocatalyst prepared by pyrolysis at 1000 °C (CoNC-CNF-1000) exhibits excellent catalytic activity toward ORR that favors the four-electron ORR process and outstanding long-term stability with 86% current retention after 40 000 s...
May 9, 2018: Small
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