Effect of Al Doping on the Photoelectrochemical OER Performance of Anisotropic SrTiO3 Crystals

Perovskite oxide photoanodes are attractive for alkaline water oxidation but are commonly limited by interfacial recombination and sluggish charge transfer. Here we enhance anisotropic SrTiO3 (STO) photoelectrodes via Al doping by simple yet effective one-step hydrothermal method and identify an optimal composition at 4% Al. In 0.1 M NaOH (pH 13) under simulated AM 1.5G illumination, 4% Al:STO exhibits 2 times enhancement in photocurrent density and 80% increase in electrochemically active surface area compared with the pristine SrTiO3, as evidenced by the reduced charge-transfer resistance and enlarged light–dark photocurrent gap. together with a markedly reduced interfacial impedance, indicating accelerated charge extraction and transfer. Band-structure analysis shows a positive shift in flat-band potential and slight band-gap narrowing after Al doping, providing more favorable carrier energetics. Steady-state and time-resolved photoluminescence further demonstrate strong PL quenching and a prolonged carrier lifetime for 4% Al:STO. ECSA analysis suggests increased electrochemically accessible surface sites at the optimal doping level. Overall, moderate Al doping synergistically tunes defects, band energetics, and interfacial kinetics to improve STO photoanodes for solar water splitting.