Nickel Ferrocyanide as High-Performance Next Generation Electrocatalyst for Urea Oxidation

Abstract Urea oxidation, a key process in energy and environmental science, faces challenges because of the insufficient understanding of its mechanism and the lack of efficient catalysts. Here we demonstrate that nickel ferrocyanide (Ni2Fe(CN)6) molecular catalyst supported on Ni form can drive urea oxidation reaction (UOR) with the record electrochemical activity and stability among all supported catalysts reported so far. A combination of kinetics data, in-situ spectroscopic measurements and energy computations suggests a new UOR pathway that delivers such outstanding performance. Different from most studied Ni-based catalysts with NiOOH derivative as a real catalytically active site for UOR, Ni2Fe(CN)6 appears to be a next-generation catalyst able to directly facilitate a two-step reaction pathway involving a critical reaction of intermediate ammonia’s production (on Ni site) and oxidation (on Fe site). Due to the alternative rate-determining step with a more favorable thermal energetics, Ni2Fe(CN)6 broke the limiting activity of the reported so far UOR catalysts. As a result, the UOR process on Ni2Fe(CN)6 can replace conventional water oxidation process in various energy-saving systems for hydrogen and hydrogen peroxide production.