Nickel ferrocyanide as a high-performance urea oxidation electrocatalyst
Date
2021
Authors
Geng, S.K.
Zheng, Y.
Li, S.Q.
Su, H.
Zhao, X.
Hu, J.
Shu, H.B.
Jaroniec, M.
Chen, P.
Liu, Q.H.
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Journal article
Citation
Nature Energy, 2021; 6(9):904-912
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Shi-Kui Geng, Yao Zheng, Shan-Qing Li, Hui Su, Xu Zhao, Jun Hu, Hai-Bo Shu, Mietek Jaroniec, Ping Chen, Qing-Hua Liu, and Shi-Zhang Qiao
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Abstract
Urea is often present in waste water but can be used in powering fuel cells and as an alternative oxidation substrate to water in an electrolyser. However, an insufficient mechanistic understanding and the lack of efficient catalysts for the urea oxidation reaction have hampered the development of such applications. Here we demonstrate that a nickel ferrocyanide (Ni₂Fe(CN)₆) catalyst supported on Ni foam can drive the urea oxidation reaction with a higher activity and better stability than those of conventional Ni-based catalysts. Our experimental and computational data suggest a urea oxidation reaction pathway different from most other Ni-based catalysts that comprise NiOOH derivatives as the catalytically active compound. Ni₂Fe(CN)₆ appears to be able to directly facilitate a two-stage reaction pathway that involves an intermediate ammonia production (on the Ni site) and its decomposition to N₂ (on the Fe site). Owing to the different rate-determining steps with more favourable thermal/kinetic energetics, Ni₂Fe(CN)₆ achieves a 100 mA cm⁻² anodic current density at a potential of 1.35 V (equal to an overpotential of 0.98 V).
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© The Author(s), under exclusive licence to Springer Nature Limited 2021