The catalytic role of Cr(VI) in promoting the degradation of organic pollutants via TiO2/SnO2/BiVO4 photoelectrocatalysis: As an electron transfer carrier.

Regarding the coexistence of heavy metals and organic pollutants, many studies have achieved synergistic removal of Cr(VI) and organic pollutants under acidic conditions. However, the role of Cr(VI) in the removal of organic pollutants under neutral conditions may have been overlooked. Here, the catalytic effect of Cr(VI) in promoting the photoelectrocatalytic degradation of organic pollutants was investigated using a ternary system, which was a combination of photocatalysis, electrocatalysis and Cr(VI) catalysis. A fabricated TiO2/SnO2/BiVO4 composite was used as an anode for degradation experiments. We found that the degradation efficiency and final removal of rhodamine B (RhB), ofloxacin (OFL), and tetracycline (TC) were improved by increasing the Cr(VI) concentration within the range of 10-20 mg L-1. And the addition of Cr(VI) sharply improved the removal of the three organic pollutants under the optimal conditions (from 65% to 96% for RhB, from 34% to 81% for OFL, and from 43% to 100% for TC). According to the results of different processing methods and quenching experiments, we proposed a new catalytic mechanism that, Cr(VI) promotes PEC degradation by acting as an electron transfer carrier between TiO2/SnO2/BiVO4 and O2.