S-scheme heterojunction constructed by ZnCdS and CoWO4 nano-ions promotes photocatalytic hydrogen production

Low-cost and efficient photocatalyst is an important aspect of photocatalytic hydrogen production. In this study, a highly efficient and stable composite photocatalyst was synthesized by assembling ZnCdS nanoparticles and CoWO4 nanoparticles. Under the 5 W LED lamp, the hydrogen production of the composite catalyst ZCS/CW-10 is as high as 839.85 mu mol in five hours, which is 5.2 times that of the pure ZnCdS photocatalyst, respectively. After four cycles, the hydrogen production still reaches 640.37 mu mol, which is 76.3% of the initial activity. This is because the introduction of CoWO4 increases the absorption of visible light by ZnCdS, and effective interface contact with each other between nanoparticles can effectively accelerate the transfer of photo generated charges between semiconductors, increase the active sites of surface hydrogen production, and achieve efficient H2 production. The staggered band structure makes ZnCdS and CoWO4 follow the electron flow scheme of S-scheme heterojunction, which is proved by in-situ XPS. The S-scheme heterostructure of ZCS/CW retains high redox potential and prolongate the lifetime of electron-generated carriers, making it more conducive to proton reduction to produce H2. This work provides a novel and convenient way to construct an efficient S-scheme heterojunction scheme, which is helpful for the rapid and effective production of metal sulfide-based photocatalysts and the rapid construction of photocatalytic water splitting hydrogen production systems. It has important research value in the utilization of new energy hydrogen energy and environmental protection.

Automated summary

This study synthesized a composite photocatalyst by assembling ZnCdS and CoWO4 nanoparticles, leading to improved efficiency in photocatalytic hydrogen production. The hydrogen production of the composite catalyst was 5.2 times higher than that of the pure ZnCdS photocatalyst, and even after four cycles, it still maintained 76.3% of the initial activity. The introduction of CoWO4 increased light absorption by ZnCdS and facilitated effective contact between nanoparticles, which enhanced the transfer of photo generated charges and increased the active sites for hydrogen production.