Investigation of visible-light-driven photocatalytic tetracycline degradation via carbon dots modified porous ZnSnO3 cubes: Mechanism and degradation pathway

It is highly desired to enhance the photocatalytic activity of ZnSnO3 owing to its potential application prospects in the photocatalytic degradation of antibiotics in water, such as the low cost, non-toxicity, simple preparation, although ZnSnO3 possesses wide band gap (similar to 3.2 eV). Herein, a novel carbon dots (CDs) modified porous ZnSnO3 cubic photocatalyst was designed and synthesized using a simple precipitation-calcination method, which was to utilize the up-conversion photoluminescence performance and the ability of electronic transfer of CDs, further broadening the visible light absorption range of the photocatalyst and accelerating the separation of the electron-hole pairs. The experimental results indicate that with the optimal CDs loading (3 wt%), the CDs modified ZnSnO3 exhibits 21 times higher degradation kinetic towards tetracycline (TC) than pure ZnSnO3. The enhanced photocatalytic activity of CDs-ZnSnO3 composites may be attributed to the increased absorption of visible light as well as the improved separation of interface charge carrier. The possible mechanism of antibiotic photodegradation in the CDs-ZnSnO3 composite photocatalytic system was proposed by active species capture experiment and electron spin resonance (ESR) technique. Furthermore, the possible photodegradation pathway of TC was proposed on the basis of the intermediates detected by liquid chromatography-mass spectrometry (LC-MS) technology. This work provides a feasible strategy for effectively applying ZnSnO3-based photocatalyst to photocatalytic degradation of antibiotics.