Oriented construction between crystal facet homojunction and S vacancies on CdS for boosting photocatalytic H2 evolution

Abstract

Though the different exposed crystal facets of cadmium sulfide (CdS) catalysts have been demonstrated to enhance their photocatalytic activity, the mechanism behind H2 evolution on these diverse facets remains elusive. Here, we synthesized CdS photocatalysts with co-exposed (101) and (002) crystal facets, incorporating S vacancies via a hydrothermal method within the temperature range from 80 to 240 °C. The resulting CdS nanorods exhibited exposed (002) and (101) crystal facets, demonstrating abundant S vacancies, and showcased a notable photocatalytic hydrogen (H2) evolution activity of 467.67 μmol g−1·h−1—approximately 144 times higher than that of CdS nanoparticles. Both experimental results and density functional theory (DFT) calculations showed the significance of co-exposed (101) and (002) crystal facets as self-constructed crystal homojunctions on CdS, facilitating efficient spatial separation of photogenerated charges. Additionally, co-exposed (101) and (002) crystal facets with S vacancies, stemming from the mismatched lattice, were observed to enhance the adsorption of water (H2O) molecules. This, in turn, reduced the energy required for H2 dissociative adsorption, providing thermodynamic advantages. The understanding of the synergistic effect between self-constructed (101) and (002) facet junctions and S vacancies on CdS for boosting photocatalytic H2 evolution holds promise for expanding the applications of CdS-based materials in various photocatalytic processes.