Surface Nd Sites Boost Charge Transfer of Fe₂O₃ Photoanodes for Enhanced Solar Water Oxidation

Photoelectrochemical (PEC) water splitting for hydrogen production is a promising technology for sustainable energy generation. In this work, we introduce Nd sites boost the PEC performance of Fe₂O₃ photoanodes through a precise gas-phase cation exchange process, which substitutes surface Fe atoms with Nd. The incorporation of Nd significantly enhances charge transfer properties, increases carrier concentration, and reduces internal resistance, leading to a substantial increase in photocurrent density from 0.44 to 0.92 mA cm^-2 at 1.23 V_RHE. Further enhancement of catalytic activity was achieved by depositing a NiCo(OH) layer and a photocurrent density of 1.15 mA cm^-2 at 1.23 V_RHE were obtained. Theoretical calculations corroborate these experimental results, revealing that Nd doping narrows the bandgap, improves charge separation efficiency, and lowers the reaction potential barrier, thereby accelerating water oxidation kinetics. These findings underscore the effectiveness of surface cation exchange and targeted metallic element doping in overcoming the intrinsic limitations of Fe₂O₃, providing a viable pathway for developing high-performance PEC systems for efficient hydrogen production.