Issue 36, 2024

Boosted urea electrooxidation activity by dynamic steady blending CoOOH–Ni(OH)2 nanoclusters for H2 production in a pH-asymmetric electrolyzer

Abstract

Electrochemical urea oxidation reaction (UOR) is a promising alternative to the oxygen evolution reaction for reducing the overall potential of the hydrogen evolution reaction during water electrolysis. The theoretical potential for the UOR is only 0.37 V versus reversible hydrogen electrode (RHE). However, the kinetics of the six-electron transfer process involved in the UOR are inherently sluggish, resulting in high overpotential during the reaction. This study designed an active catalyst with a lower kinetic barrier in the UOR by fabricating blending CoOOH–Ni(OH)2 nanoclusters through the structural transformation of amorphous Co–Ni hydroxide films. This structural transformation was investigated using high-angle annular dark-field scanning transmission electron microscopy, corresponding energy-dispersive X-ray spectroscopy, and in situ X-ray absorption spectra. The blending CoOOH–Ni(OH)2 nanoclusters exhibited superior electrocatalytic activity in the UOR in an alkaline environment, achieving a low onset potential of 1.24 V (vs. RHE) in 1 M KOH with 0.5 M urea. We employed the CoOOH–Ni(OH)2 nanoclusters as anodic electrocatalysts in a two-cell electrolyzer for asymmetric electrocatalysis. Hydrogen could be produced at a remarkable current density of 10 mA cm−2 at a low applied potential of only 0.45 V. Density functional theory calculations revealed that blending CoOOH–Ni(OH)2 nanoclusters with more oxygen vacancies exhibited a lower Gibbs free energy for the intermediate reaction pathway of NCONH2 → NCONH, compared with the fine structure of CoNiOx (x = 2–3). This study lays down a novel pathway for developing new blending electrocatalysts to be used in electrochemical reactions.

Graphical abstract: Boosted urea electrooxidation activity by dynamic steady blending CoOOH–Ni(OH)2 nanoclusters for H2 production in a pH-asymmetric electrolyzer

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Article information

Article type
Paper
Submitted
19 Jun 2024
Accepted
08 Aug 2024
First published
09 Aug 2024

J. Mater. Chem. A, 2024,12, 24126-24135

Boosted urea electrooxidation activity by dynamic steady blending CoOOH–Ni(OH)2 nanoclusters for H2 production in a pH-asymmetric electrolyzer

S. Peng, S. Chang, C. Chang, P. HN, C. Chang, K. Wu, Y. Huang, Y. Chen, T. Kuo, C. Pao, J. Chen and D. Wang, J. Mater. Chem. A, 2024, 12, 24126 DOI: 10.1039/D4TA04241G

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