Blade-like Structures of a ZnSe/NiSe Heterojunction on Flexible Ni Foil for Enhanced Photoelectrochemical Water Oxidation

The growing energy crisis and environmental degradation from fossil fuels have accelerated the pursuit of sustainable green hydrogen generation via sunlight-driven photoelectrochemical (PEC) water splitting. In this work, we present the fabrication of a ZnSe/NiSe heterojunction comprising hierarchically blade-like NiSe structures grown on a flexible Ni foil substrate with conformal ZnSe overlayers with the help of the combination of chemical vapor deposition and a magnetron sputtering system. Field emission scanning electron microscopy analysis reveals a vertically aligned blade-like NiSe morphology, while the core-level shifts characterized by X-ray photoelectron spectroscopy reflect the interfacial electronic interactions. High-resolution transmission electron microscopy illustrates the good crystallinity of ZnSe deposited on blade-like NiSe structures grown on Ni foil. This architecture enables enhanced light absorption, increased active surface area, and efficient charge separation via a favorable heterojunction. As a result, the PEC measurements of the ZnSe/NiSe photoanode demonstrate a markedly enhanced photocurrent density of ∼0.35 mA/cm 2 when biased at 0.8 V vs RHE, outperforming bare NiSe (∼0.19 mA/cm 2 ). The synergistic effect of interfacial engineering and morphological optimization offers a promising strategy for the development of efficient, scalable, and flexible roll-to-roll PEC devices for solar hydrogen production.