BiVO4/WO3−x S-scheme heterojunctions with amplified internal electric field for boosting photothermal-catalytic activity

Abstract

Modulating the internal electric field (IEF) remains a critical challenge for S-scheme heterojunction photocatalysts. The BiVO₄/WO_3−x S-scheme heterojunctions were successfully prepared to purify the wastewater environment where TC and Cr (VI) coexist under visible light illumination. The BiVO₄/WO_3−x with 10 wt% WO_3−x (BVO/WO_3−x-10) demonstrated superior photocatalytic efficiency, which could degrade 78.5 % of TC and reduce 85.3 % of Cr(VI) in 60 min. The photocatalytic activity of BVO/WO_3−x−10 displayed enhanced removal efficiency in the mixed system. The removal ability of TC and Cr (Ⅵ) was increased by 1.29 and 1.32 times, respectively. Based on IR thermography measurements, the elevated reaction system temperatures were ascribed to the photothermal effect of WO_3−x. Oxygen vacancies (OVs) could amplify the energy band difference between WO_3−x and BiVO₄, which strengthens the IEF and accelerates the separation of carriers. A detailed degradation pathway and intermediate toxicity were carried out using the mung bean experiment and the results of the LC−MS. In general, this work provided new insights for regulating IEF to enhance the degradation efficiency in mixed wastewater and the carriers separation in the S-scheme heterojunction of the photothermal-catalytic system.