Direct Z-Scheme Co3o4 Quantum Dots/Bi2moo6 Heterostructure for Rapid Tetracycline Degradation : Performance, Degradation Pathways and Mechanism Insight

To improve the photocatalytic performance of Bi 2 MoO 6 , a direct Z-scheme Co 3 O 4 quantum dots/Bi 2 MoO 6 heterojunction was designed and prepared via a simple solvothermal reaction. The structural and morphological characterization showed that nano-scale Co 3 O 4 quantum dots (Co 3 O 4 QDs) were uniformly distributed on the surface of three-dimensional (3D) Bi 2 MoO 6 microsphere without changing the original morphology of each other. The as-prepared Co 3 O 4 QDs/Bi 2 MoO 6 microspheres exhibited substantially enhanced activity for the removal of tetracycline (TC) as compared to pure Bi 2 MoO 6 in the visible light exposure. The photocatalyst composite of 10%-Co 3 O 4 QDs/Bi 2 MoO 6 showed the optimum photocatalytic activity ( k = 0.048 min -1 ), which was about 6.0 and 1.7 times higher than Co 3 O 4 QDs ( k = 0.008 min -1 ) and Bi 2 MoO 6 ( k = 0.028 min -1 ), respectively. The possible degradation pathways of TC under the Co 3 O 4 QDs/Bi 2 MoO 6 photocatalytic system were analyzed based on the intermediates monitored by liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/Q-TOF MS). Capture experiments of active species and electron spin resonance (ESR) spectra demonstrated that h + , ·OH, and ·O 2 − radicals all participated in photocatalytic degradation, and ·O 2 − radical was the leading active species. The excellent photocatalytic performance of 3D Z-scheme Co 3 O 4 QDs/Bi 2 MoO 6 heterojunction photocatalyst makes it a promising photocatalyst for the degradation of tetracycline antibiotics