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

Abstract

The NiMoV LDH/NF electrode realizes high-efficiency catalysis for UOR in view of the rapid kinetics, high intrinsic activity and robust durability in variable urea concentration and pH values conditions. • Mo and V dopants in NiMoV LDH optimizes the electronic structure to facilitate the in-situ conversion of Ni 3+ species. • Co-doping of Mo and V atoms in NiMoV LDH enhances the adsorption energy of Ni site to urea molecule during UOR process. • 1.40 V is required to achieve 100 mA cm −2 in urea oxidation for NiMoV LDH in alkaline. • The NiMoV LDH electrode is suitable for a wide range of urea concentrations and pH changes. 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.