Surface Activation of NiMo Oxyfluoride/Fe-Oxyhydroxide Heterostructures via Defect Engineering for Enhanced...

Efficient photoelectrochemical water oxidation critically depends on bulk conductivity and effective charge separation at the semiconductor electrolyte interface. Herein, we report a hybrid heterostructure design strategy using nickel molybdenum oxyfluoride (NiMoOF) with iron oxyhydroxide (FeOOH), synthesized through a hydrothermal synthesis route combined with subsequent spray pyrolysis. The hybridization of NiMoOF and FeOOH in a NiMoOF/FeOOH hybrid heterostructure significantly increases the surface-active area and promotes interfacial charge transfer by passivating surface defects, compared to pristine NiMoOF. As a result, the NiMoOF/FeOOH hybrid heterostructured photoanode exhibits a markedly enhanced photocurrent density of 2.18 mA cm^-2 at 1.23 V vs. RHE, substantially outperforming pristine NiMoOF. The photoanode also demonstrates excellent operational stability maintained over 20 h under 1.5 illumination. Furthermore, quantitative analysis reveals significant improvements in both bulk (η_bulk = 28.91%) and surface (ηs_urface = 90.38%) charge separation efficiencies. This work demonstrates a scalable and effective strategy for designing high-performance photoanodes through synergistic compositional and interfacial engineering, offering valuable insights into advanced photoelectrochemical water-splitting systems.