A novel route to synthesize Bi/β-Bi2O3@carbon: mechanism and performance for efficient degradation of organic pollutants†

Abstract

Metastable β-Bi₂O₃ exhibits high catalytic performance due to its suitable band gap, greater dielectric permittivity and conductivity. However, the difficultly in preparing β-Bi₂O₃ and β-Bi₂O₃ based materials is still a problem to be overcome. In this work, porous Bi/β-Bi₂O₃@carbon photocatalysts were prepared for the first time by using an atmosphere switching strategy during the post-cooling of metal–organic framework (MOF) pyrolysis. The crystal phase structure and composition of Bi/β-Bi₂O₃@carbon could be easily adjusted by simply switching the cooling atmosphere from N₂ to air when cooled to different temperatures. The photocatalytic activities of the material were evaluated by degradation of emerging pollutant fluorescent whitening agent (FWA) 351 under simulated solar light irradiation. It was observed that 10 mg L⁻¹ FWA 351 was completely degraded within 4 h using the optimal photocatalyst. The mineralization efficiency reached 60% in 6 h. Active species trapping experiments confirmed that hole oxidation was responsible for the degradation of FWA 351. The increased activity was due to the improved visible light utilization resulted from the reduced bandgap of Bi/β-Bi₂O₃@carbon and the surface plasmon resonance effect of bismuth metal, as well as the facilitated interfacial electron migration and charge carrier separation through multi-interface transfer paths. The proposed strategy provides new ideas for designing and synthesizing functional materials. The efficient degradation and mineralization of FWA 351 with Bi/β-Bi₂O₃@carbon also confirmed its potential for future application in wastewater treatment.