Boosting charge separation and broadening NIR light response over defected WO3 quantum dots coupled g-C3N4 nanosheets for photocatalytic degrading antibiotics

Enhancing charge separation and broadening the light response are important factors to achieve effective photocatalysts for the degradation of antibiotics. Herein, defected WO3 quantum dots (WOQD) are coupled to graphitic carbon nitride (g-C3N4, CN) nanosheets via WOQD prepared by a one-pot solvothermal method followed by self-assembly through a wet chemical method. Meanwhile, WOQD with the size of ~ 2 nm, defect surface, and quantum size facilitate coupling with CN to obtain a high-quality interface. Radical trapping control experiments and photocatalytic degradation experiments confirmed that the WOQD/CN nanocomposites display high activities in the photo-degradation of ciprofloxacin (CIP) and tetracycline (TC) in antibiotic pollutants in the presence of hydroxyl(·OH) and superoxide radicals(·O2−),and the photo-degradation activities of the optimized WOQD(3)–CN sample are seven times higher than those of CN under Xe light irradiation. According to surface photovoltaic spectroscopy, photoluminescence measurements, Kelvin probe force microscopy, and photoelectrochemical measurements, the enhanced photocatalytic activity of nanocomposites in the degradation of antibiotic pollutants may be attributed to the enhanced charge separation due to the Z-scheme heterojunction formed under UV–vis light irradiation and the broadening of the light response to the near-infrared (NIR) region due to the localized surface plasmon resonance effect under NIR light irradiation. In addition, the effects of various factors including pH, initial solution concentration, and common cations and anions (i.e., SO42−, HCO3−, and NO3−) on the degradation of CIP and TC were evaluated. This work highlights the highly efficient charge transfer of WOQD-CN photocatalysts and their great potential for high-efficiency broadband photocatalysis.