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

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) was electrodeposited on the top of the CuCo layer (Ni(OH)/CuCo/Ni(OH)), 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, which outperformed the potential required for individual components, Ni(OH) and CuCo. The high density of Ni active sites in the composite structure facilitated high electrocatalyst activity and stability. Ni(OH)/CuCo/Ni(OH) 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)/CuCo/Ni(OH) 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.