NiSx modulated spatial charge separation in CdS-based heterojunctions for photocatalytic hydrogen evolution

Photocatalytic hydrogen evolution, a promising clean energy conversion technology, faces efficiency limitations due to the mismatched timescales between sub-picosecond bulk photocarrier recombination and microsecond-scale surface reaction. Herein, a dual-strategy involving selenium decoration and NiS_x cocatalyst loading was proposed to ameliorate the carrier dynamics bottleneck in CdS-based photocatalysts. The in situ loading of NiS_x cocatalysts established an interfacial built-in electric field (BIEF) that enabled spatially oriented carrier separation and transfer, while the selenium modification optimized the light absorption range and Fermi energy level, obtaining an increase in the photocarrier concentration and further modulated the BIEF. Femtosecond transient absorption spectroscopy revealed a dual-channel carrier dynamics enhancement mechanism that BIEF-driven directional charge migration synergistically coupled with NiS_x-mediated holes trapping. This synergistic effect achieved an approximately tenfold enhancement of hydrogen evolution rate (461.71 μmol h⁻¹) relative to that of bare CdS under visible light (> 420 nm). This study elucidated the regulatory mechanism of element decoration and cocatalyst loading on carrier dynamics, providing an insight for designing high-performance photocatalysts.