Enlarged CoO Covalency in Octahedral Sites Leading to Highly Efficient Spinel Oxides for Oxygen Evolution Reaction |
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| Authors: | Ye Zhou Shengnan Sun Jiajia Song Shibo Xi Bo Chen Yonghua Du Adrian C Fisher Fangyi Cheng Xin Wang Hua Zhang Zhichuan J Xu |
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| Affiliation: | 1. School of Materials Science and Engineering, Nanyang Technological University, Singapore, Singapore;2. Institute of Chemical and Engineering Sciences A*STAR, Singapore, Singapore;3. Department of Chemical Engineering, University of Cambridge, Cambridge, UK;4. College of Chemistry, Nankai University, Tianjin, China;5. School of Chemical and Biomedical Engineering, Nanyang Technological University, Singapore, Singapore;6. Solar Fuels Laboratory and Energy Research Institute, Nanyang Technological University, Singapore, Singapore;7. Energy Research Institute@NTU, ERI@N, Interdisciplinary Graduate School, Nanyang Technological University, Singapore, Singapore;8. Singapore‐HUJ Alliance for Research and Enterprise, NEW‐CREATE Phase II, Campus for Research Excellence and Technological Enterprise (CREATE), Singapore, Singapore |
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| Abstract: | Cobalt‐containing spinel oxides are promising electrocatalysts for the oxygen evolution reaction (OER) owing to their remarkable activity and durability. However, the activity still needs further improvement and related fundamentals remain untouched. The fact that spinel oxides tend to form cation deficiencies can differentiate their electrocatalysis from other oxide materials, for example, the most studied oxygen‐deficient perovskites. Here, a systematic study of spinel ZnFexCo2?xO4 oxides (x = 0–2.0) toward the OER is presented and a highly active catalyst superior to benchmark IrO2 is developed. The distinctive OER activity is found to be dominated by the metal–oxygen covalency and an enlarged Co?O covalency by 10–30 at% Fe substitution is responsible for the activity enhancement. While the pH‐dependent OER activity of ZnFe0.4Co1.6O4 (the optimal one) indicates decoupled proton–electron transfers during the OER, the involvement of lattice oxygen is not considered as a favorable route because of the downshifted O p‐band center relative to Fermi level governed by the spinel's cation deficient nature. |
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| Keywords: | cation deficiency decoupled proton– electron transfers metal– oxygen covalency oxygen evolution reaction spinel oxides |
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