Anion intercalation of NiMn-LDH accelerating urea electrooxidation on trivalent nickel

Abstract

Reducing the urea oxidation reaction (UOR) barriers is a key knot for accelerating its practical applications. Here, we demonstrate that NiMn-LDH with sulfate anion interaction can enable urea electrooxidation with a low anodic potential of 1.36 V at 100 mA cm⁻². We find that the UOR on NiMn-LDH is driven by Ni³⁺ species and the Ni³⁺ generation is the rate-determining step of UOR. Both the Mn doping and sulfate anion interaction contribute to the low-barrier phase transformation from Ni(OH)₂ to NiOOH to produce the Ni³⁺ state with high activity in UOR, owing to that Mn doping optimizes the electronic states and intercalation of guest anions weakens the interlayer interactions, which ultimately tunes Ni³⁺ generation kinetics toward the superior UOR activity. Our findings provide new insights into the design of the highly active UOR catalysts.