Interface-Engineered Ni-Coated CdTe Heterojunction Photocathode for Enhanced Photoelectrochemical Hydrogen Evolution

Photoelectrochemical (PEC) water splitting for hydrogen production using the CdTe photocathode has attracted much interest due to its excellent sunlight absorption property and energy band structure. This work presents a study of engineered interfacial energetics of CdTe photocathodes by deposition of CdS, TiO2, and Ni layers. A heterostructure CdTe/CdS/TiO2/Ni photocathode was fabricated by depositing a 100-nm n-type CdS layer on a p-type CdTe surface, with 50 nm TiO2 as a protective layer and a 10 nm Ni layer as a co-catalyst. The CdTe/CdS/TiO2/Ni photocathode exhibits a high photocurrent density (Jph) of 8.16 mA/cm2 at 0 V versus reversible hydrogen electrode (VRHE) and a positive-shifted onset potential (Eonset) of 0.70 VRHE for PEC hydrogen evolution under 100 mW/cm2 AM1.5G illumination. We further demonstrate that the CdTe/CdS p-n junction promotes the separation of photogenerated carriers, the TiO2 layer protects the electrode from corrosion, and the Ni catalyst improves the charge transfer across the electrode/electrolyte interface. This work provides new insights for designing noble metal-free photocathodes toward solar hydrogen development.