Synergistic optimization of surface reconstruction and active site construction: GaAs/NiO/Cu(OH)2 for photoelectrochemical water splitting

Abstract

The construction of an appropriate band structure has been demonstrated to be an effective method of promoting carrier transport and enhancing the photoelectrochemical (PEC) water splitting performance of electrodes. This study successfully fabricated a GaAs/NiO/Cu(OH)₂ electrode via surface reconstruction and electrochemical deposition techniques and the electrode exhibits outstanding performance in PEC water splitting. Specifically, the surface reconstruction process was utilised to modify GaAs/Ni, thereby forming a composite structure GaAs/Ni–NiO. The type-II heterojunction formed between GaAs and NiO enhances the separation efficiency of photogenerated carriers, effectively suppressing carrier recombination. Meanwhile, the surface plasmon resonance effect of Ni significantly broadens the electrode's light absorption range, enhancing solar energy utilization efficiency. A uniform layer of Cu(OH)₂ was deposited on the heterojunction surface via electrochemical deposition. This reaction layer provides abundant active sites for the reaction. The results indicate that the GaAs/NiO/Cu(OH)₂ electrode exhibits a current density of 23.29 mA cm⁻² at 1.23 V vs. RHE (a 11.9-fold increase compared to the pure GaAs electrode) and achieves an applied bias photon-to-current efficiency (ABPE) of 16.3%. After 10 000 seconds of continuous operation, the electrode stability has significantly improved. The present study proposes a multiscale surface engineering synergistic strategy, offering a novel approach for highly efficient photoelectrochemical water splitting technology.