Efficient spatial charge separation in unique 2D tandem heterojunction CdxZn1−xIn2S4–CdS–MoS2 rendering highly-promoted visible-light-induced H2 generation

Abstract

Two-dimensional (2D) semiconductor nanostructures have exhibited great prospect as an efficient photocatalyst for solar-to-fuel application. In this work, a unique 2D tandem heterojunction consisting of ultrathin Cd_xZn_1−xIn₂S₄ nanosheets coupled with rectangular CdS flakes and defect-rich MoS₂ few-layered nanosheets was constructed for the first time. Remarkably, the efficient electron transfer channels present in the CdS/Cd_xZn_1−xIn₂S₄ and Cd_xZn_1−xIn₂S₄/MoS₂ 2D tandem heterojunctions facilitate the spatial separation and directional migration of photo-induced charge carriers effectively. Moreover, such 2D tandem heterojunction Cd_xZn_1−xIn₂S₄–CdS–MoS₂ is provided with excellent light harvesting capacity and abundant HER active sites from the defective MoS₂ co-catalyst. These distinct advantages endow the optimized C_0.15ZIS–5C–3M hybrid (5 wt% CdS, 3 wt% MoS₂) with an exceptional photocatalytic H₂ evolution reaction (HER) activity of 27.14 mmol h⁻¹ g⁻¹, approximately 47 times that of pure ZnIn₂S₄ and it is much superior to that of Pt-decorated C_0.15ZIS–5C and most ZnIn₂S₄-based composites reported previously. A high HER apparent quantum yield (AQY) of 19.97% is achieved at λ = 400 nm. In addition, both the cycling and long-term HER measurements evidence the prominent stability of C_0.15ZIS–5C–3M for H₂ production. The results indicated here could pave the way for the exploitation of new 2D heterostructures toward highly-efficient solar conversion and utilization.