Effect of oxygen vacancies on photoelectrochemical properties of amphoteric semiconductor Bi4Ti3O12 photoelectrode

Bi4Ti3O12 (BTO) photoelectrodes were fabricated by a sol-gel spin coating method and oxygen vacancy (OV) concentrations in BTO were regulated through a following heat-treatment in different atmospheres. Based on the results of XRD, XPS and HRTEM, OVs have been introduced in BTO after Ar processing. An interesting p/n type amphoteric photo-response characteristic was discovered in BTO as demonstrated by the LSV, CV plots and open-circuit photovoltage measurement. The typical amphoteric photo-response characteristic of BTO should be related to its special Fermi level structure and accordingly minor band bending in the interface between BTO and the electrolyte. The positive photocurrent density of Ar-BTO is 0.75 μA/cm2 at 0.5 V vs. Ag/AgCl, which is 4.4 times over that of BTO, and its photocurrent onset potential showed an obvious negative shift (∼0.1 V) in relative to BTO. The charge carrier densities of Ar-BTO was over 60% higher than that of BTO. The enhanced photoelectrochemical properties of Ar-BTO was ascribed to its abundant OVs which effectively inhibited recombination, boosted carrier injection efficiency and activated electrode surface as demonstrated by the EIS and PL characterizations. These findings provide new perspective for fabricating new type bismuth-based photoelectrodes and optimizing its photoelectrochemical performance.