Building Directional Charge Transport Channel in CdTe-Based Multilayered Photocathode for Efficient Photoelectrochemical Hydrogen Evolution
Xiangyan Chen, Zhuocheng Yin, Kun Cao, Shaohua Shen
Abstract
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.