Effective regulation on catalytic performance of nickel–iron–vanadium layered double hydroxide for urea oxidation via sulfur incorporation

Abstract

The effective regulation of catalytic active sites and reaction kinetics has been the key to promoting an efficient urea oxidation reaction (UOR). Herein, well-defined nickel–iron–vanadium layered double hydroxide nanosheets modified by sulfur incorporation (S-NiFeV LDH) on a nickel foam substrate are synthesized by a facile two-step hydrothermal method. Benefiting from the improved intrinsic activity and electrical conductivity derived from sulfur doping, and the large specific surface area of nanosheet architectures, the as-prepared S-NiFeV LDH catalyst shows a superior electrocatalytic performance with a low potential of 1.38 V at the current density of 100 mA cm⁻² and the Tafel slope of 30.1 mV dec⁻¹ in 1.0 M KOH and 0.33 M urea electrolyte. In addition, it displays robust stability while operating sustainably for 25 h at 50 mA cm⁻² without any distinct activity attenuation. The results of density functional theory (DFT) calculations further indicate that the introduction of sulfur is more conducive to the adsorption of urea molecules on the catalyst surface, and the optimized Gibbs free energy of CO(NH₂)₂* decomposition and desorption of CO* and NH* in the S-NiFeV LDH catalyst facilitate accelerating the reaction kinetics of the UOR. Accordingly, this work provides a potential strategy for developing highly-efficient electrocatalysts for the UOR.