TiO2 protection layer and well-matched interfaces enhance the stability of Cu2ZnSnS4/CdS/TiO2 for visible light driven water splitting

Abstract

Cu₂ZnSnS₄-Based heterostructure materials present broad spectral absorption and a high absorption coefficient in the visible region; however, their photocatalytic activity and stability are still impeded due to photochemical corrosion. In this paper, Cu₂ZnSnS₄/CdS/TiO₂, a double-heterojunction photocatalyst fabricated with a TiO₂ protection layer and well-matched interface architecture, has been prepared by a multi-step liquid phase process. The chemically inert TiO₂ protective layer on the catalyst surface restrained the catalyst photocorrosion induced by formed nascent O₂ and remarkably enhanced the catalyst stability during photocatalytic water splitting. Structural characterization and theoretical simulation indicated that both interfaces between Cu₂ZnSnS₄–CdS and CdS–TiO₂ showed highly well-matched type-II alignment, which was beneficial to the separation and transfer of photoinduced charge pairs. The Cu₂ZnSnS₄/CdS/TiO₂/Pt catalyst under visible light achieved photocatalytic water splitting and the H₂ evolution rate of the catalyst reached 8.76 μmol g⁻¹ h⁻¹. The catalyst activity has been maintained in multi-cycle experiments without significant decay, and its stability has been confirmed by measuring the Cd²⁺ concentration in the catalyst dispersion using the ICP-OES method. This work can offer a new route to design more stable and efficient Cu₂ZnSnS₄-based heterostructure materials for solar-driven photocatalytic water splitting to produce H₂.