Rational Design of NiFeO _X and Cobalt‐Integrated Hydroxyapatite Nanoarchitecture on BiVO ₄ Photoanode for Enhanced and Durable Solar to Water Oxidation

ABSTRACT Solar‐driven photoelectrochemical (PEC) water splitting offers a sustainable route to solar‐to‐fuel conversion; however, its practical application is hindered by sluggish oxygen evolution reaction (OER) kinetics and severe surface charge recombination. BiVO 4 (BVO) is a promising photoanode material but suffers from inefficient charge separation and limited operational stability. Herein, we report a dual‐catalyst strategy in which cobalt‐incorporated hydroxyapatite (Co‐HAP) is synergistically integrated with NiFeO X nanosheets to simultaneously enhance OER activity and durability. The optimized BVO/NiFeO X /Co‐HAP photoanode achieves a photocurrent density of 6.36 mA·cm −2 at 1.23 V vs reversible hydrogen electrode (RHE) under AM 1.5G illumination in neutral phosphate electrolyte, nearly sevenfold higher than pristine BVO. Comprehensive analyses reveal that the NiFeO X /Co‐HAP nanosheet framework promotes efficient interfacial charge extraction, establishes a favorable surface electric field, and suppresses hole‐electron recombination. The 2D nanoarchitecture provides abundant Co active sites, while interfacial NiFeO X accelerates hole extraction and facilitates electron transfer from Ni to V sites, thereby mitigating V 5+ dissolution. Notably, the photoanode demonstrates extended operational stability of ≈120 h in a phosphate electrolyte. This work highlights a robust design strategy that leverages the synergistic ion‐exchange capacity of HAP and the charge‐extraction ability of NiFe catalysts to advance efficient and durable PEC water‐splitting systems.