NiCo₂O₄ Electrocatalyst Doped with Phosphorus for Improved Oxygen Evolution Reaction

Spinel oxides are affordable transition-metal electrocatalytic materials, but their low conductivity and intrinsic activity restrict their wide application in electrolyzed water catalysts. In this study, a series of heterojunction samples comprising phosphorus-doped spinel oxides NiCo 2 O 4 in collaboration with g-C 3 N 4 (NCP x @C 3 N 4, x = 0.25, 0.50, 0.75) were fabricated through a straightforward mixture method for water splitting. Therein, the NCP 0.5 @C 3 N 4 electrocatalyst exhibits remarkable performance compared to the other synthesized compounds, demonstrating a small overpotential of 247 mV at 10 mA cm –2 for the oxygen evolution reaction (OER), a favorable Tafel slope of 48 mV dec –1, and decent durability. The collaborative interaction between phosphorus doping and g-C 3 N 4 results in the creation of numerous oxygen defects, increasing the electrochemically active surface area in NCP 0.5 @C 3 N 4 and demonstrating a direct enhancement of the OER. Density functional theory (DFT) calculations verified that the introduction of phosphorus and its collaboration with g-C 3 N 4 effectively regulated the electronic structure and optimized the d-band center position. Based on the results, a resilient synergistic interaction between NCP 0.5 and C 3 N 4 sheets contributes to the enhanced electrocatalytic activity of NCP 0.5 @C 3 N 4 .