NiO@GaN Nanorods-Based Core-shell Heterostructure for Enhanced Photoelectrochemical Water Splitting via Efficient Charge Separation

Abstract

Remarkable properties of III-V semiconductors, particularly GaN nanostructured based photoelectrodes offers a potential attention in the field of photoelectrochemical water splitting (PEC-WS) for clean and sustainable hydrogen production, due to its wide bandgap, magnificent optoelectrical properties. However, the presence of inevitable surface states in GaN nanorods (NRs) leads to low solar-to-hydrogen (STH) conversion efficiency with poor stability, thereby severely limiting their practical application in PEC-WS, which can be effectively alleviated by constructing a hybrid heterostructure. Herein, we present the development of interfacial engineering of a type-II core-shell heterostructure based on p-NiO nanoparticles (NPs) loaded on n-GaN NRs photoelectrodes for PEC-WS. We assessed the impact of the NiO NPs shell density on core GaN NRs, finding that the optimized NiO@GaN NRs photoelectrode achieved a photocurrent density (Jph) of 1.38mA/cm² at 1.23V versus RHE and an excellent applied bias photo-to-current conversion efficiency (ABPE) of ~0.39%, which was 3.8 (Jph) and 4.8 (ABPE)-fold times higher than the pristine GaN NRs photoanode under 1-Sun illumination. The type-II p-n heterojunction band alignment between core-shell NiO@GaN NRs photoelectrode effectively reduced the photogenerated carrier recombination rate through surface states passivation and boost the light absorption and harvesting capacity. This facilitates a significant charge separation and transfer at the photoanode/electrolyte interface leading to enhanced redox reactions, resulting in improved PEC-WS and STH performances. These findings offer a promising strategy to design and fabricate highly efficient III-V heterostructures-based photoelectrodes for futuristic PEC-WS green energy applications.