Microwave-assisted surface attachment of aluminium ions on in situ diluted titanium-doped hematite photoanodes for efficient photoelectrochemical water-splitting

In this work, we introduce in situ diluted (ISD) hydrothermal synthesis of a titanium-doped Fe₂O₃ photoanode and suggest a novel microwave-assisted surface attachment (MASA) method for fabricating an aluminium-titanium co-doped photoanode. The charge-carrier density of a hematite photoanode increases with Ti⁴⁺ doping, which offers lower bulk resistance. Through MASA treatment, Al³⁺ ions can be attached homogeneously on the surface of a Ti-FeOOH film from aqueous aluminium chloride. The charge recombination is weaker after the successful diffusion of Al³⁺ and partial formation of self-induced Al₂O₃, which acts as a surface passivation layer. The synergistic interaction of Al co-doping and surface passivation cathodically shifts the onset potential by 120 mV and enhances the photocurrent density to 1.32 mA cm⁻² (1.23 V vs. RHE). MASA treatment not only improves the bulk characteristics of the photoanode but also enhances the surface injection efficiency which promotes water-splitting. The charge-transfer mechanism for the prepared photoanodes was also studied extensively.