Co-Catalytic Effect and Mechanism of Ni/Co Codoped Prussian Blue and Zr Doping on the Photoelectrochemical Water Splitting of α-Fe ₂ O ₃

The escalating global energy demand and the pressing need to mitigate climate change have intensified the search for sustainable and clean energy alternatives. Hydrogen, produced via the solar-driven photoelectrochemical (PEC) water splitting process, stands out as a promising carbon-free energy carrier. Herein, Zr-doped α-Fe₂O₃ was combined with Ni/Co codoped Prussian blue to construct a NiCoPBAs/Zr-Fe₂O₃ (NCPB/ZF) photoanode. The photon absorption efficiency, charge carrier separation efficiency, and injection efficiency of this composite photoanode were significantly improved. The NCPB/ZF had the highest photocurrent density of 2.41 mA cm⁻², which was 5.9 times higher than α-Fe₂O₃ with 0.41 mA cm⁻² at 1.23 V (vs RHE) under AM 1.5G light irradiation. The NCPB/ZF had a lower Tafel slope of 55.5 mV decade⁻¹ compared to 138.8 mV decade⁻¹ for α-Fe₂O₃, so the water oxidation kinetics over NCPB/ZF was remarkably advanced. The free energy of PEC water oxidation over NCPB/ZF was significantly decreased as the OER overpotential was lowered to 0.46 V from 1.75 V for α-Fe₂O₃. Consequently, the NCPB/ZF demonstrated significantly increased photoelectrocatalytic activity for the evolution of oxygen via water oxidation.