DFT and experimental investigations on the photocatalytic mechanism of C3N4-MQDs/BWO heterojunction for Tetracycline degradation

Abstract

BackgroundThe development of efficient antibiotic degradation catalysts has attracted much attention from researchers, but little is known about the intrinsic relationship between the geometry, electronic structure, and photocatalytic activity of the catalysts. MethodsHerein, a magnetic recoverable C3N4-MQDs/BWO heterojunction was successful synthesized by combining C3N4 magnetic quantum dots with Bi2WO6 nanosheets through a hydrothermal method. Significant FindingsThe prepared CMBW-2 (C3N4-MQDs/BWO with 2% C3N4-MQDs) was applied to degraded TC (tetracycline) solution of 20mg·L−1 under visible light irradiation, presenting 100% conversion within 120 min, and the reaction rate is 13.8 times and 2.3 times that of Bi2WO6 and g-C3N4/Bi2WO6, respectively. Its stability tests show an unchanged activity after five cycles for a long 600 min visible light irradiation. Various characterization results confirm that the good catalytic performance originates from the formation of a heterojunction to facilitate the separation of generated electron–hole pairs, while its larger specific surface area provides more active adsorption sites. DFT results show that the Bi2WO6(001)/C3N4(002) heterostructure is a staggered band arrangement structure whose VBM (valance band maximum) is mainly inhabited by atomic orbitals of Bi2WO6, while its CBM (conduction band minimum) is mainly inhabited by atomic orbitals of C3N4(002). Based on DFT and experimental results, an indirect Z-scheme is proposed, in which Fe3O4 nanoparticles are regarded as an electronic conductive bridge to realize rapid electron transfer. Moreover, the C3N4-MQDs/BWO heterojunction has high potential for practical applications in the removal of emerging contaminants in sewerage because of its excellent stability and sufficient magnetism.