A Cd‐Free Electron Transport Layer Simultaneously Enhances Charge Carrier Separation and Transfer in Sb2Se3 Photocathodes for Efficient Solar Hydrogen Production

Abstract Efficient photoelectrochemical (PEC) water splitting is a pivotal technique to achieve sustainable hydrogen production, driving the exploration for high‐performance photoelectrodes. Antimony selenide (Sb 2 Se 3 ) semiconductor has received significant attention due to its cost‐effectiveness, eco‐friendly nature, and favorable photoelectric properties. However, traditional Sb 2 Se 3 ‐based photocathodes typically employ cadmium sulfide (CdS) as an electron transport layer (ETL), which introduces toxicity and stability issues, hindering their commercial application potential. This study develops a versatile method to improve the PEC performance of Sb 2 Se 3 ‐based photocathodes by incorporating Cd‐free (Zn,Sn)O ETL. Comprehensive investigations demonstrate remarkable improvement in surface and heterojunction interface properties, leading to charge carrier dynamics optimization with highly interesting carrier separation efficiency of 96.5% and transfer efficiency of 93.6%. As a result, the champion Mo/Sb 2 Se 3 /(Zn,Sn)O/TiO 2 /Pt photocathode delivers a notable photocurrent density ( J ph ) of 31.8 mA cm −2 (close to its theoretical value), and a half‐cell solar‐to‐hydrogen (HC‐STH) conversion efficiency of 4.32%. This advancement highlights a promising pathway toward large‐scale and environmentally friendly solar hydrogen production applications.