Oxygen vacancy-suppression strengthened the internal electric field in ZnIn2S4/BiVO4 S-scheme heterojunction to boost photocatalytic removal of aqueous pollutants

Abstract

The impact of internal electric field intensity (IEF) within step-scheme (S-scheme) heterojunctions is profound on photocatalytic performance. Furthermore, the presence of oxygen vacancies in the photocatalysts has a significant influence on their photocatalytic characteristics. Thus, a ZnIn2S4/BiVO4 S-scheme heterojunction was strategically engineered for photocatalytic degradation. The modulation of oxygen vacancy levels in the oxidation photocatalyst (OP) was utilized to adjust the IEF within the S-scheme heterojunctions. BiVO4 with controlled oxygen vacancies was synthesized using a simple approach, and the impact of oxygen vacancies on the charge transfer across the heterojunction was thoroughly examined. Subsequently, various characterization results, verified that the IEF in the heterojunction with suppressed oxygen vacancy levels (10 %BV-600) was stronger, while those with elevated vacancy levels (10 %BV-400) showed weaker IEFs. Comprehensive results confirmed that the S-scheme heterojunction is formed between ZnIn2S4 and BiVO4. Under visible irradiation, the 10 %BV-600 sample demonstrated remarkable photocatalytic activity, achieving a 96.4 % degradation of methyl orange within 60 min. Intriguingly, the rate constants for methyl orange removal for the 10 %BV-600 sample were approximately 3 and 27 times greater than those of the individual ZnIn2S4 and BiVO4, respectively. Moreover, the photocatalytic performance of the 10 %BV-400 sample, which had a lower IEF, was inferior to that of the 10 %BV-600 sample. These results underscore the superior photocatalytic capabilities of heterojunctions with a strengthened IEF due to suppressing oxygen vacancy. This work provides insights into the role of oxygen vacancy in regulating IEF intensity in heterojunctions.