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-Fe 2 O 3 was combined with Ni/Co codoped Prussian blue to construct a NiCoPBAs/Zr–Fe 2 O 3 (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-Fe 2 O 3 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-Fe 2 O 3, 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-Fe 2 O 3 . Consequently, the NCPB/ZF demonstrated significantly increased photoelectrocatalytic activity for the evolution of oxygen via water oxidation.