Carbon quantum dots/BiVO4 S-scheme piezo-photocatalysts improved carrier separation for efficient antibiotic removal

Reasonable design of an efficient S−scheme photocatalyst remains an ongoing challenge due to the limitation of interfacial charge separation efficiency. Herein, CQDs/BiVO4 S−scheme heterojunction with Bi−O−C bond was synthesized by introducing carbon quantum dots (CQDs) growth on BiVO4 piezo−photocatalyst and absorbed visible light up to 750 nm. Under light + ultrasonic conditions, the reaction rate constant (k) of BVO/C−0.10 reached 0.0517 min−1 on tetracycline (TC) degradation, which was 2.24 and 4.04 times higher than those of BiVO4 and CQDs, respectively. The enhanced performance was attributed to the improved efficiency of the photogenerated carrier separation, originating from the combination of piezoelectric effect and S−scheme heterojunction with Bi−O−C bond. The Bi−O−C bond at the CQDs (3–8 nm) and BiVO4 interfaces connected the two semiconductor materials and provided an atomic−level interface channel for carrier migration. The piezoelectric properties of the composites were investigated by piezo−response force microscopy (PFM). Based on Mott−Schottky curves, X−ray photoelectron spectroscopy (XPS), and scavenging experiments, the possible piezo−photocatalytic mechanism was proposed in combination with the band structures and characteristics of CQDs and BiVO4. This work furnishes unique insights into developing efficient S−scheme piezo−photocatalysts for purifying wastewater.