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 H2-evolution reactions are highly required for improving its H2-production efficiency. In this study, a facile noble metal-free strategy was reported to simultaneously realize the efficient charge separation and rapid interfacial H2-evolution reaction by homojunction CdS photocatalysts with a massive S2–-adsorbed surface phase in a sulfur-rich system. Herein, massive S2–-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 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 H2-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 H2-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 H2-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 H2-generation active centers to boost the H2 formation. This study may provide new ideas to one-step construct highly efficient photocatalysts for water splitting.