Heterojunctions of ZnS with Zn vacancies and hexagonal CdS pyramids for photocatalytic hydrogen production

Metal sulfides with suitable morphology typically possess efficient solar light utilization and suitable band structures for photocatalytic hydrogen production. However, a significant challenge is faced in developing the optimal morphology of individual semiconductors and precisely modulating hybrid heterostructures. Herein, this work reports the superior photocatalytic hydrogen evolution performance of hexagonal CdS pyramids compared to other nanostructured CdS catalysts. Additionally, ZnS nanoparticles with zinc vacancies are grown in situ on the surface of the hexagonal CdS pyramids, meticulously constructing a Z-scheme heterojunction of CdS/ZnS. By elaborately adjusting the ratio of Cd to Zn sources, the interfacial structure of the heterojunction can be optimized to significantly reduce the obstruction of charge transfer. With the same concentrations of Cd and Zn sources, the CdS/ZnS heterojunction hexagonal pyramid-nanoparticle morphology exhibits a significantly enhanced photocatalytic hydrogen evolution rate of 4660 mu mol h-1 g-1 under visible light, which is 4.6 and 84.72 times higher than those of pristine CdS pyramids and ZnS nanoparticles, respectively. The electron paramagnetic resonance (EPR) results comprehensively demonstrate the promoted interfacial charge separation in the Z-scheme CdS/ZnS. This work provides an effective strategy for the rational design of catalyst morphology and construction of Z-scheme heterojunction photocatalysts for efficient photocatalysis.