Generalized Synthetic Strategies toward Oxygen Vacancy-Enriched ZnO–ZnS Hollow Porous Spheres with Enhanced Photocatalytic Hydrogen Evolution

Abstract

Constructing a hollow porous ZnO–ZnS sphere is still a big challenge due to the difficulty in controlling the morphology and distribution of ZnO shell originating from the fact that ZnO prefers to grow along particular crystal planes. Here, we demonstrate a novel synthetic strategy for the preparation of oxygen-vacancy-enriched ZnO–ZnS hollow porous (Ov-ZOS (HP)) spheres by combining the concepts of adopting a template-directed method, selecting the sulfidation precursor, and tuning the calcination process of the template. Structural characterization and density functional theory (DFT) calculations reveal that hollow porous nanostructures and oxygen vacancies in the ZnO–ZnS heterojunction are beneficial in promoting efficient charge transfer and separation. The optimized Ov-ZOS (HP) exhibits enhanced rates of hydrogen evolution reaction (71.86 mmol h^–1 g^–1), which is 1.48, 2.08, and 3.0 times higher than those of ZnO–ZnS hollow porous spheres, oxygen vacancy-enriched ZnO–ZnS nanosheets, ZnO–ZnS nanosheets, respectively. Moreover, the Ov-ZOS (HP) presents excellent cyclability for photocatalytic hydrogen evolution. Therefore, this study provides physical insights into controlling the hollow porous nanostructures of various semiconductor heterojunctions that are hard to form through other existing strategies for solar energy utilization.