Regulating d-band electrons of sulfur-enriched CoSx to weakening the S-Hads bond in CoSx/ZnCdS Ohmic heterojunctions for enhanced photocatalytic hydrogen evolution

Abstract

Modifying transition metal sulfides to expose more active sites is one way to enhance photocatalytic activity. In this work, ZnCdS was anchored on the surface of CoSx by in-situ hydrothermal method, thereby constructing a ZnCdS/CoSx ohmic heterojunction and achieving directional electron transfer from ZnCdS to sulfur rich CoSx. Among them, CoSx was modified by sulfur enrichment and amorphization. The modified CoSx can expose more S active sites, effectively weaken S-Hads bonds, and promote the desorption process of hydrogen gas. In addition, after the formation of heterojunctions, the broad spectral response of CoSx can effectively enhance the visible light absorption ability of ZnCdS, improve the utilization of visible light, and facilitate the hydrogen evolution reaction (HER) process. Specifically, ZnCdS/CoSx-20 exhibits a significant hydrogen evolution rate of 28.4 mmol g-1 h-1 under visible light irradiation, which is approximately 9.8 times that of pure ZnCdS (2.9 mmol g-1 h-1). Density functional theory (DFT) calculations indicate that a significant negative shift in the d-band center in ZnCdS/CoSx heterojunctions, which is beneficial for the weaken S-Hads bond and desorption process of hydrogen gas. In situ XPS further confirm the charge transfer direction and prove increase surface charge density of CoSx. This work provides new insights into the design of ZnCdS based heterojunctions to achieve effective charge transfer.