Coupling NiMn-Layered Double Hydroxide Nanosheets with NiCo2S4 Arrays as a Heterostructure Catalyst to Accelerate the Urea Oxidation Reaction

The rational design of advanced transition-metal-based electrocatalysts with a heterostructure is a promising strategy for the promotion of the urea oxidation reaction (UOR) for energy-conservation technologies, but achieving a sufficiently high performance remains a challenge. In this work, we report a dramatic improvement in the UOR performance of a heterostructured electrocatalyst that combines NiMn-layered double hydroxide (LDH) nanosheets with NiCo2S4 arrays via a series of facile hydrothermal fabrication steps. Due to the high-flux electron transfer pathways at the close-contact interface, abundant active sites, and unique three-dimensional (3D) architecture, the NiCo2S4@NiMn LDH heterostructure grown on nickel foam exhibits a low potential of 1.37 V at a current density of 100 mA·cm–2 and a low Tafel slope of 43.8 mV·dec–1. More impressively, the proposed electrocatalyst demonstrates robust stability of more than 25 h at a current density of 50 mA·cm–2 with a negligible decrease in activity. In addition, density functional theory calculations reveal that the interface engineering within the heterostructure is beneficial for the adsorption and activation of urea molecules and the improvement of the sluggish UOR dynamics. The dissociation of adsorbed CO(NH2)2* into CO* and NH* intermediates on the heterostructured NiMn LDH is also facilitated by electronic coupling with NiCo2S4, resulting in superior UOR performance.