Synergistic interfacial effects in NiFe layered double hydroxide-coupled ZnO/α-Fe2O3 photoanodes toward improved photoelectrochemical functionality

Abstract

In this study, we develop ternary heterojunction photoanodes with a hierarchical structure by electrodepositing a NiFe Layered Double Hydroxide (NiFe-LDH) cocatalyst onto ZnO/α-Fe₂O₃ (ZF) heterojunction materials. Surface imaging reveals that the distinct structures of ZnO nanosheets, α-Fe₂O₃ nanorods, and NiFe-LDH nanosheets are linked to improved photoelectrochemical performance. A ladder-like Type-II band alignment in the ZnO/α-Fe₂O₃/NiFe-LDH (ZFL) architecture promotes efficient separation of photogenerated electrons and holes, thereby suppressing recombination and enhancing the visible-light photoresponse, reducing recombination and enhancing visible light absorption. We also propose how changing the Ni/Fe molar ratio in NiFe-LDH affects performance, confirmed by compositional analysis. The NiFe-LDH cocatalyst speeds up surface oxidation by forming NiOOH intermediates, which increases the electrode's hydrophilicity and decreases charge transfer resistance. This research proposes a strategy that combines band structure control and surface wettability improvement to boost photoelectrochemical efficiency in ternary heterostructures.