Simultaneous removal of Cr(vi) and TC over BiO1−XBr/CeVO4 S-scheme heterostructures: oxygen vacancy boosted charge separation and analysis of intermediates

Abstract

The exploration of simultaneous photocatalytic removal of chromium (Cr(VI)) and tetracycline (TC) in sewage is still rare. Herein, oxygen vacancy (OV)-rich BiO_1−XBr/CeVO₄ (3 : 1) (3BOr–CeV) S-scheme composite dual-responsive photocatalysts were successfully synthesized. The photocatalytic degradation rate of TC over 3BOr–CeV was 4.90 times and 1.67 times higher than those over CeVO₄ (CeV) and BiO_1−XBr (BOr). Meanwhile, the reduction rate of Cr(VI) over 3BOr–CeV reached about 74.20 and 3.51 times compared with those over CeV and BOr. Interestingly, the synergistic photocatalytic activity of 3BOr–CeV was enhanced, and the reduction ability for Cr(VI) was increased by 2.03 times in the mixed system. Such gratifying catalytic activities were attributed to the enhanced charge trapping and light absorption capacity by OVs, together with the strong redox capability and streamlined photoinduced charge separation ability in the S-scheme. The pathway of TC degradation in complex solution systems was monitored by liquid chromatography-mass spectrometry (LC-MS). The DFT calculations, XPS, and PL indicated that the S-scheme heterojunction could promote the separation of charge carriers. In addition, EPR, UV-vis DRS, and finite element calculations demonstrated that the OVs could broaden the light absorption range and capture the charge carriers. This work provided a promising way to modulate the application of S-scheme heterojunction photocatalysts to degrade mixed wastewater.