Realizing Efficient Photoelectrochemical Performance for Well-Designed CdS@ZnIn2S4 Heterostructure Photoanode with Directional Interfacial Charge Transfer Dynamics

Abstract

Designing a heterostructure photoanode with an appropriate band alignment, a beneficial charge migration pathway, and an adequate interfacial coupling is crucial for photoelectrochemical (PEC) energy conversion. Herein, we fabricate a hetero-nanostructure photoanode with CdS nanorods (CdS NRs) and two-dimensional (2D) ZnIn2S4 nanosheets (ZIS NSs) via a two-step in situ growth method on FTO glass to acquire a sufficient interfacial contact between two semiconductors. Based on their electronic band structures, the CdS is designed to be firstly grown on FTO to act as a photoelectron transport layer and 2D ZIS is further fabricated on the CdS as a photohole accumulation layer to directly contact the electrolyte. Benefitting from the Type II band alignment between the CdS and ZIS, such a heterostructure significantly enhances the separation efficiency and prolongs the lifetime of photocarriers. More importantly, it ensures that photoholes accumulate on the 2D ZIS with a highly exposed surface area for an oxidation reaction at the surface-active sites, while the photoelectrons transfer to counter electrode for hydrogen evolution. The optimum CdS@ZIS heterostructure photoanode exhibits a superior PEC performance with a photocurrent of 4.19 mA/cm2 at 1.23 VRHE (two times that of the CdS and eight times that of ZIS) and an applied bias photo-to-current efficiency (ABPE) of 1.93% at 0.49 VRHE. This work can inspire the future design of heterostructure photoanodes for highly efficient solar energy conversion.