Facile regrowth of Mg-Fe2O3/P-Fe2O3 homojunction photoelectrode for efficient solar water oxidation

Abstract

The photoelectrochemical (PEC) water splitting performance of hematite-based photoanodes is still far from their theoretical value due to the ultrafast charge recombination in bulk and on the surface. In response, we developed a regrowth strategy to fabricate a photoanode with metallic Mg-doped α-Fe₂O₃ coating on nonmetallic P-doped α-Fe₂O₃ nanorods (Mg-Fe₂O₃/P-Fe₂O₃ NRs). This homojunction structure fulfils the requirements of both high charge separation efficiency and favorable band alignment, showing a high photocurrent density (4.7-fold higher than pristine Fe₂O₃) and low onset potential of 0.68 V_RHE. Experimental and density functional theory (DFT) results reveal that the origin of such superior PEC performance is P-doping and Mg-Fe₂O₃ coating, which efficiently eliminate lattice mismatching, improve the conductivity of hematite, and simultaneously promote the photogenic carriers separation by the built-in electric field. This promising design may open an avenue to fabricating various efficient homojunction photoanodes for practical PEC water splitting.