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.