Building Directional Charge Transport Channel in CdTe-Based Multilayered Photocathode for Efficient Photoelectrochemical Hydrogen Evolution

Modulating the band alignment of semiconducting photoelectrodes is essential for efficient carrier transport and consequently optimized photoelectrochemical performances. Herein, a CdS/TiO2 bilayer is coated on a CdTe absorber via chemical bath deposition and magnetron sputtering, successively, to build directional interfacial charge transfer channels for efficient photoelectrochemical hydrogen evolution. The obtained multilayered CdTe/CdS/TiO2/Pt photocathode yields a dramatically increased photocurrent density of −9.6 mA cm–2 at −0.4 V vs reversible hydrogen electrode (RHE) under simulated sunlight (AM 1.5 G, 100 mW cm–2). It is well evidenced that, with the CdS/TiO2 bilayer coated onto CdTe, the CdTe/CdS/TiO2 heterojunction, with a well aligned band structure, generates favorable conduction band offset, energetically facilitating electron transfer from CdTe to CdS, and then to TiO2. Moreover, the CdTe/CdS/TiO2/Pt photocathode shows good stability for water reduction due to the TiO2 protective layer stabilizing against the photocorrosion of CdTe/CdS. This study provides referable guidance for designing multilayer photoelectrodes for stable and efficient solar water splitting from the viewpoint of interface energetics engineering.