Improved photocarrier separation in Ga/Fe gradient (Ga, Fe)2O3 thin films

Metal oxides are promising photoanode materials for photoelectrochemical reactions due to their chemical stability and low-cost synthesis. However, their high photocarrier recombination rate limits their commercial applications. One strategy to promote photocarrier separation efficiency in metal oxides is building an inner electric field through band engineering techniques. In this study, a gradient band structure was prepared in (Ga, Fe)2O3 thin films on F:SnO2 (FTO) coated glass substrate by varying the Ga/Fe ratio. The performance of the gradient photoanode was evaluated by measuring its photocatalytic activity with photocurrent. The forward gradient photoanode, with increasing Ga/Fe ratio from bottom substrate to photoanode surface, exhibited a higher photocurrent density (0.44 mA/cm2 at 1.23 V vs reversible hydrogen electrode (RHE) under AM 1.5G illumination) compared to the reverse gradient photoanode with decreasing the Ga/Fe ratio in the same situation. The forward gradient band structure, which facilitates photocarrier separation and transportation, was believed to play a dominant role in improving the photocatalytic performance. This work demonstrates an effective strategy to improve photocarrier separation and photocatalytic performance of metal oxide photocatalysts through band engineering.