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) photo catalyst, 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 similar to 5 nm and with massive S2--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 S2--adsorbed c-CdS nanoparticles, and the c-CdS/h-CdS (7 wt %) achieved a H-2-production rate of 1789.2 mu mol h(-1) g(-1), about 2.3 times higher than that of the h-CdS (795.1 mu mol 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 S2- ions; namely, the surface homojunction of hexagonal and cubic CdS can facilitate the spatial charge separation, while numerous adsorbed S2- 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.