Heterogeneous Engineering of Ni–Co–S Nanosheets for Efficient Urea Electrolysis

Nickel-based catalysts have been identified as highly promising electrodes for the urea oxidation reaction (UOR) because of their abundant reserves, flexible structures, and tunable valence states. However, there is a challenge in catalytic activity that needs to be addressed for nickel-based catalysts for more effective and practical applications. Here, a strategy of introducing a promoter via preparing a nickel–cobalt–sulfides nanosheets arrays electrode self-supported on nickel foam (Ni–Co–S NSAs/NF) with heterogeneous NiS, Ni3S2, and Co3S4 compounds is proposed to boost high-efficiency UOR. Through electrochemical analysis complemented by in situ Raman spectroscopy assessments, the Ni–Co–S NSAs/NF catalyst attained a noteworthy low potential of 1.34 V relative to the reversible hydrogen electrode at 200 mA cm–2, with Ni3+-O as the principal active site. Theoretical calculations demonstrated that the Co3S4 promoter facilitated the formation process of the NiOOH phase and the initial urea adsorption during urea electrolysis, thus improving the UOR activity of the Ni–Co–S NSAs/NF electrodes.