Ni–Co–Mn Trimetallic Nanoparticles as Hierarchical Electrocatalysts for Highly Efficient Urea Oxidation via Spatial Decoupling

Urea electrooxidation (UOR) is one of the most efficient technologies for the conversion of chemical energy to hydrogen or electric energy. Nickel-based catalysts can impetuate UOR but result in urea peroxidation. Seeking a balance between reaction selectivity and reaction kinetics, that is, trading off energy utilization efficiency against the energy conversion rate, is a necessary choice for designing UOR catalysts. Therefore, we designed Co, Mn codoped NiS2 trimetallic nanoparticles at the expense of partial UOR selectivity. The optimal catalyst shows a high urea electrooxidation activity of 77 mA cm–2 at 1.5 V (vs RHE) and good stability. A series of electrochemical experiments combined with in situ electrochemical mass spectrometry and XPS unveiled the effect of each metal sites clearly. The doped Mn is beneficial to oxidizing the adjacent urea molecules, which modulate the UOR pathway and initiate urea peroxidation. Besides, the electron exchange between Co–Ni accelerates the urea oxidation of Ni and accelerates the oxidation of CO. The combination of the three improves the UOR catalytic performance of the material. Our work paves the way for the rational design and synthesis of highly efficient nanocatalysts to achieve industrial energy conversion and economic hydrogen production.