In-situ generated hydrogen pump boosting photocatalytic hydrogen evolution over ZnCdS/MoO3-x under visible light irradiation

Photocatalytic water splitting for hydrogen evolution (PHE) is an effective and sustainable strategy to alleviate energy shortages and environmental issues. However, active hydrogen (H*), as a critical intermediate, has low generation and desorption rates that limit the development of PHE. Herein, a ZnCdS/MoO 3-x heterojunction is prepared by a two-step solvothermal method and applied to a photocatalytic hydrogen evolution reaction under visible light conditions. The band structure and electron spin resonance (ESR) confirm the formation of an S-scheme heterojunction in ZnCdS/MoO 3-x , promoting the utilization of photo-generated carriers and thereby enhancing H* generation on ZnCdS. Furthermore, in-situ ESR, quasi in-situ Raman spectroscopy and in-situ DRFTIRS spectroscopy demonstrate that the H* is subsequently transferred from ZnCdS to MoO 3-x via the hydrogen spillover effect. The H* is then confined within the lattice of MoO 3-x and forms H x MoO 3-x in situ. Finally, the electrochemical tests and DFT calculations demonstrate that the H x MoO 3-x acts as a “hydrogen pump”, lowering the H* desorption barriers and ultimately enhancing the hydrogen evolution of the system. Therefore, the optimum hydrogen evolution rate of ZnCdS/MoO 3-x reaches 7.9 mmol·g −1 ·h −1 , which is 26.3 times higher than that of pure ZnCdS, along with a hydrogen storage capacity of 0.36 wt%. This work offers a novel approach for achieving efficient and sustained PHE reactions by modulating the generation and desorption rates of the intermediate H*.