Modulating electronic structure of ternary NiMoV LDH nanosheet array induced by doping engineering to promote urea oxidation reaction

Fabrication of advance electrocatalysts for urea oxidation reaction (UOR) is of great significance for purifying urea-enriched wastewater and producing hydrogen. Here, a doping engineering strategy is adopted to obtain a ternary NiMoV layered double hydroxide (LDH) nanosheet array supported on the three-dimensional (3D) nickel foam substrate. The synergistic effect brought by the unique 2D/3D hierarchical structure could expose more active sites and accelerate charge and mass transfer. In addition, experimental and theoretical results confirm that Mo and V dopants are capable of modifying the local electronic structure of Ni sites to optimize the adsorption energy for urea molecules. Therefore, the as-prepared NiMoV LDH/NF electrode realizes high-efficiency catalysis for UOR in view of the rapid kinetics, high intrinsic activity and robust durability. Specifically, NiMoV LDH/NF electrode presents a low potential of 1.40 V to deliver 100 mA cm−2 for UOR, which is about 260 mV less for its urea-free counterpart in alkaline electrolyte. When anodic NiMoV LDH/NF electrode and cathodic Pt/C electrode are integrated into a two-electrode system for water electrolysis in variable urea concentration and pH values conditions, urea-assisted electrolysis water system exhibit the lower potential (≤1.63 V) than that of conventional water electrolysis at 100 mA cm−2. This work shows that the local electronic structure adjustment of the active site caused by the heteroatom doping effect could improve the electrocatalytic oxidation performance of some small molecules.