Hierarchical bismuth vanadate photoanode comodified with cobalt-iron Prussian blue analogue and nickel-oxhydroxide for efficient solar water oxidation

Photoelectrochemical (PEC) water splitting offers a sustainable approach to solar energy conversion, but is limited by charge recombination and sluggish oxygen evolution kinetics. Herein, a rationally designed ternary photoanode (BiVO₄/NiOOH/CoFe-PBA) is fabricated via layer-by-layer assembly. The NiOOH interlayer enhances hole extraction and transport owing to its superior hole mobility, thereby effectively suppressing charge recombination. Simultaneously, the CoFe-PBA overlayer serves as both a cocatalyst and a protective layer. Collectively, NiOOH and CoFe-PBA decrease the energy barrier for water oxidation. Significant improvements in photogenerated charge extraction, transport, and separation have been achieved through multidimensional optimization. The resulting BiVO₄/NiOOH/CoFe-PBA photoanode achieves an exceptional photocurrent density of 5.67 mA/cm² at 1.23 V vs. RHE, representing a 7.8-fold improvement over pristine BiVO₄. This performance enhancement is reflected in outstanding charge injection (94.3 %) and separation (68.3 %) efficiencies, as well as a 290 mV negative shift in onset potential. This work demonstrates a robust interface engineering strategy for developing high-performance photoanodes.