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/TiO₂bilayer 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^-2at -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/TiO₂bilayer coated onto CdTe, the CdTe/CdS/TiO₂heterojunction, 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 TiO₂protective 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.