Polyvinylpyrrolidone in the one-step synthesis of carbon quantum dots anchored hollow microsphere Bi2WO6 enhances the simultaneous photocatalytic removal of tetracycline and Cr (VI)

The development of visible-light-responsive catalysts that are capable of simultaneous photo-oxidation and photo-reduction has been a major focus of research. In this study, carbon quantum dots anchored hollow microsphere Bi2WO6 (CQDs/HBWO) photocatalyst was successfully prepared via a one-step polyvinylpyrrolidone (PVP)-assisted hydrothermal method. PVP had a dual function: controlling hollow microsphere morphologies as well as serving as a precursor of carbon quantum dots. The as-prepared CQDs/HBWO-18 had the highest catalytic activity for the photocatalytic degradation of TCH (0.02768 h -1), which was approximately 2.1 and 1.23 times higher than that for the hollow microsphere Bi2WO6 without CQDs and the nanosheet Bi2WO6, respectively. Only CQDs/HBWO-18 was effective for the photoreduction of Cr (VI) in the system without pH adjustment or scavenger addition. The photoreduction efficiency of Cr (VI) increased 83% and 58% in the bipollutant system with 5 mg/L and 10 mg/L of Cr (VI) containing 20 mg/L TCH compared with Cr (VI) alone. The improved photoreduction activity of Cr (VI) could be attributed to TCH acting as a photogenerated hole scavenger. The results of the scavenging test and electron spin resonance confirmed that h+, center dot O2 and center dot OH were the main reactive species. Eventually, the possible degradation pathway of TCH was proposed.

Automated summary

This study successfully prepared a visible-light-responsive catalyst, carbon quantum dots anchored hollow microsphere Bi2WO6 (CQDs/HBWO), which showed high catalytic activity for the photocatalytic degradation of TCH. The presence of carbon quantum dots significantly improved the photoreduction efficiency of Cr (VI) in the bipollutant system by acting as a photogenerated hole scavenger, with h+, center dot O2 and center dot OH identified as the main reactive species.