Tunable crystal structure of Cu–Zn–Sn–S nanocrystals for improving photocatalytic hydrogen evolution enabled by copper element regulation

Abstract Hydrogen energy is a powerful and efficient energy resource, which can be produced by photocatalytic water splitting. Among the photocatalysis, multinary copper-based chalcogenide semiconductor nanocrystals exhibit great potential due to their tunable crystal structures, adjustable optical band gap, eco-friendly, and abundant resources. In this paper, Cu–Zn–Sn–S (CZTS) nanocrystals with different Cu content have been synthesized by using the one-pot method. By regulating the surface ligands, the reaction temperature, and the Cu content, kesterite and hexagonal wurtzite CZTS nanocrystals were obtained. The critical factors for the controllable transition between two phases were discussed. Subsequently, a series of quaternary CZTS nanocrystals with different Cu content were used for photocatalytic hydrogen evolution. And their band gap, energy level structure, and charge transfer ability were compared comprehensively. As a result, the pure hexagonal wurtzite CZTS nanocrystals have exhibited an improved photocatalytic hydrogen evolution activity.