Photocatalytic mechanism and performance of a novel wool flake–BiFeO <sub>3</sub> nanosheet–TiO <sub>2</sub> core–shell-structured composite photocatalyst
Tianyu Chen, Hui Zhang, Ye Han, Haoshuai Gu, Limeng Yang, Hailiang Wu, Ningtao Mao
Abstract
Abstract In this study, BiFeO 3 (BFO) nanosheets ground from BFO particles were first incorporated with wool flakes to construct sandwich-like wool–BFO composites using the vibration-assisted ball milling technique in freezing conditions. The wool–BFO composites were then loaded with a thick layer of TiO 2 nanoparticles to prepare the core–shell-structured wool–BFO–TiO 2 composites using a hydrothermal synthesis process. The microstructure of the core–shell wool–BFO–TiO 2 composites and its photocatalytic applications were systematically examined using a series of characterization methods. Trapping experiments and electron spin resonance spectra were also employed to judge the active radical species like superoxide radicals (·O 2 − ), singlet oxygen ( 1 O 2 ), holes (h + ), and hydroxyl radicals (·OH) using benzoquinone, furfuryl alcohol, ethylenediamine tetraacetic acid, and tert-butanol as the scavengers, respectively. The photodegradation performance of the wool–BFO–TiO 2 composites was measured using more resistant methyl orange (MO) dye as the pollutant model. In comparison with the wool–TiO 2 or wool–BFO composites, the superior photocatalytic properties of the wool–BFO–TiO 2 composites under visible light irradiation were attributed to the presence of mesopores and macropores, the large specific surface area and intimate interface between wool–BFO composites and TiO 2 nanoparticles, the coexistence of Fe 3+ , Fe 2+ , Bi 3+ , Bi (3–x)+ , Ti 4+ , and Ti 3+ species, and the strong visible light harvesting, thus leading to the fast separation of photogenerated electron–hole pairs. The wool–BFO–TiO 2 composites could be used for the repeated photodegradation of organic pollutants and be recycled easily using a magnet. The active radical species of the wool–BFO–TiO 2 composites were ·O 2 − and 1 O 2 rather than ·OH and h + , which were involved in the photodegradation of MO dye under visible light irradiation.