Orbital Hybridization Modulation via Ni Atom Decoration in Phosphotungstic Acid Cluster Cocatalyst for Optimized Photocatalytic Hydrogen Evolution Kinetics

Regulating the hydrogen adsorption and desorption behavior on the cocatalyst surface can effectively improve the performance of photocatalytic hydrogen production. While platinum-group materials excel in optimizing Fermi levels and proton reduction kinetics, their practical application is hindered by economic and scalability constraints. Herein, a novel Ni atom decorated phosphotungstic acid cluster (PTA-Ni) is developed as a cocatalyst integrated with graphitic carbon nitride (GCN) for photocatalytic hydrogen evolution. Theoretical and experimental analyses demonstrate that the PTA-Ni cocatalyst significantly enhances photoinduced carrier separation efficiency compared to pristine PTA, acting as an optimized electron acceptor. Mechanistic investigations reveal that Ni atom doping induces contraction of the structure and orbital electron redistribution within the [WO₆] octahedron, strengthening the p-d orbital hybridization between W and O atoms. This electronic modulation effectively reduces hydrogen adsorption energy (ΔG_H* = -0.75 eV) and accelerates H^* intermediate desorption kinetics. Under visible light irradiation, the optimized GCN-PTA-Ni photocatalyst achieves a hydrogen production rate of 1.40 mmol g^-1 h^-1, outperforming the benchmark GCN-Pt system by 4.4-fold. This work provides atomic-level insights into the orbital engineering of polyoxometalate cocatalysts, offering a strategic pathway to design high-performance photocatalytic systems through targeted electronic structure manipulation.