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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 VRHE. 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. [ABSTRACT FROM AUTHOR]