Dual Modification Strategy: Passivation Layer and Cocatalyst on Hematite for Improved Photoelectrochemical Water Oxidation

α-Fe₂O₃ is a very attractive photoanode for photoelectrochemical (PEC) water decomposition. However, its short diffusion length, poor conductivity, and fast charge-carrier recombination severely limit device efficiency. Here, coloading an Al₂O₃ passivation layer and a CoO_x cocatalyst onto Ti-doped α-Fe₂O₃ was carried out to promote PEC water oxidation by improving charge separation and transfer at the electrode/electrolyte interface and inhibiting photocarrier recombination. The optimized Ti:Fe₂O₃/Al₂O₃/CoO_x photoanode shows a large photocurrent density of 1.41 mA cm^-2 at 1.23 V vs reversible hydrogen electrode, which is 47 times greater than that of a pristine Ti:Fe₂O₃ photoanode. The dual modifications with a combined passivation layer and cocatalyst on the photoanode verify a valuable way for solar energy conversion in PEC water oxidation.