Homojunction CdS Photocatalysts with a Massive S²–-Adsorbed Surface Phase: One-Step Facile Synthesis and High H₂-Evolution Performance

For the traditional hexagonal CdS ( h -CdS) photocatalyst, both of the efficient charge separation and rapid H 2 -evolution reactions are highly required for improving its H 2 -production efficiency. In this study, a facile noble metal-free strategy was reported to simultaneously realize the efficient charge separation and rapid interfacial H 2 -evolution reaction by homojunction CdS photocatalysts with a massive S 2– -adsorbed surface phase in a sulfur-rich system. Herein, massive S 2– -adsorbed c -CdS nanoparticles as the effective surface phase were deposited on the h -CdS photocatalyst surface by an adsorption in situ transformation strategy. The obtained c -CdS nanocrystals with a nanocrystal size of ∼5 nm and with massive S 2– -ion adsorption can be homogeneously dispersed on the whole h -CdS surface to form c -CdS/ h -CdS photocatalysts. Photocatalytic activity evaluation revealed that the H 2 -production performance of the h -CdS photocatalyst could be markedly enhanced by modifying S 2– -adsorbed c -CdS nanoparticles, and the c -CdS/ h -CdS (7 wt %) achieved a H 2 -production rate of 1789.2 μmol h –1 g –1, about 2.3 times higher than that of the h -CdS (795.1 μmol h –1 g –1 ). The improved H 2 -generation activity of c -CdS/ h -CdS can be accounted by the excellent synergistic effect of c -CdS nanocrystals and S 2– ions; namely, the surface homojunction of hexagonal and cubic CdS can facilitate the spatial charge separation, while numerous adsorbed S 2– ions on the c -CdS nanocrystal surface can effectively function as H 2 -generation active centers to boost the H 2 formation. This study may provide new ideas to one-step construct highly efficient photocatalysts for water splitting.