Tailored Ni(OH)2/CuCo/Ni(OH)2 Composite Interfaces for Efficient and Durable Urea Oxidation Reaction

Abstract

Electrocatalytic urea oxidation reaction is a promising alternative to water oxidation for more efficient hydrogen production due to its significantly lower thermodynamic potential. However, achieving efficient electrochemical urea oxidation remains a formidable challenge, and development of an improved electrocatalyst with an optimal physicochemical and electronic structure toward urea oxidation is desired. This can be accomplished by designing a tailored two-dimensional composite with an abundance of active sites in a favorable electronic environment. In this study, we demonstrate the fabrication of a self-supported, electrochemically grown metal/mixed metal hydroxide composite interface via a two-step electrodeposition method. Specifically, Ni(OH)₂ was electrodeposited on the top of the CuCo layer (Ni(OH)₂/CuCo/Ni(OH)₂), and the resultant 2D composite structure required 1.333 ± 0.006 V to oxidize urea electrochemically to achieve a current density of 10 mA cm^–2, which outperformed the potential required for individual components, Ni(OH)₂ and CuCo. The high density of Ni³⁺ active sites in the composite structure facilitated high electrocatalyst activity and stability. Ni(OH)₂/CuCo/Ni(OH)₂ was stable for at least 50 h without any noticeable degradation in the activity or alteration of the morphology. As a bifunctional electrocatalyst, the material also exhibited excellent performance for water oxidation with 260 mV overpotential and 50 h stability. In a two-electrode configuration coupled with a NiMo cathode catalyst, the electrolyzer required 1.42 V cell voltage for overall urea splitting. Overall, the engineered Ni(OH)₂/CuCo/Ni(OH)₂ composite demonstrated exceptional potential as an efficient and stable electrocatalyst for both urea and water oxidation reactions, paving the way for more effective hydrogen production technologies.