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 NiCo2O4 in collaboration with g-C3N4 (NCPx@C3N4, x = 0.25, 0.50, 0.75) were fabricated through a straightforward mixture method for water splitting. Therein, the NCP0.5@C3N4 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-C3N4 results in the creation of numerous oxygen defects, increasing the electrochemically active surface area in NCP0.5@C3N4 and demonstrating a direct enhancement of the OER. Density functional theory (DFT) calculations verified that the introduction of phosphorus and its collaboration with g-C3N4 effectively regulated the electronic structure and optimized the d-band center position. Based on the results, a resilient synergistic interaction between NCP0.5 and C3N4 sheets contributes to the enhanced electrocatalytic activity of NCP0.5@C3N4.