In Situ Synthesis of Strongly Coupled Co2P-CdS Nanohybrids: An Effective Strategy To Regulate Photocatalytic Hydrogen Evolution Activity

Noble-metal-free photocatalyst Co2P-CdS was synthesized via a facile in situ hydrothermal method for the first time to boost the performance of photocatalytic H2 production. This synthesis process allows the Co2P nanoparticles to disperse evenly on the surface of CdS sub-microspheres and to form unique intimate contact interfaces. The physical and photophysical properties of as-prepared Co2P-CdS composite samples were characterized by X-ray diffractometry, transmission electron microscopy, UV–vis diffusion reflectance spectroscopy, X-ray photoelectron spectroscopy, photoluminescence, and surface photovoltage (SPV) spectroscopy. The results indicate that the photocatalytic H2 evolution activity of CdS sub-microspheres under visible-light irradiation is significantly enhanced by introducing inexpensive Co2P as co-catalyst. The Co2P-CdS sample with a loading of 1.2 mol% Co2P gives the highest H2 production rate of 0.303 mmol·h–1, which was about 3 times higher than that achieved with 0.5 wt% Pt-loaded CdS sample. After further introduction of K2HPO4 as sacrificial agent, the H2 production rate reached 0.356 mmol·h–1, which is 41 times higher than that obtained with pure CdS. The apparent quantum yield of the Co2P-decorated CdS sample is about 13.88% at 420 nm. These results suggest that the synergistic effect between Co2P and CdS greatly enhances the photocatalytic activity of CdS. Moreover, a reasonable mechanism for the enhanced photocatalytic activity was proposed through density functional theory calculation and verified by SPV spectroscopy.