Synthesis of mesoporous BiOBr 3D microspheres and their photodecomposition for toluene

Graphical abstract: Display Omitted Highlights: → Mesoporous bismuth oxybromide (BiOBr) microspheres assembled by nanosheets were synthesized by a simple solvothermal route. → It was reported for the first time that mesoporous BiOBr microspheres were used to degrade gas phase toluene. → The intermediates under different irradiation source were identified and the relationship between intermediates and reaction rate constant was discussed. → Fifteen kinds of intermediates were detected through GC-MS analysis, and a tentative degradation pathway was proposed. - Abstract: In this article, a facile solvothermal method was introduced to synthesize mesoporous BiOBr microspheres with Bi(NO3)3 as Bi source. The synthesized catalysts were characterized by XRD, SEM, TEM, XPS, UV-vis, TG-DTA, and N2-adsorption-desorption, and their photoactivity was evaluated by gaseous toluene both under UV and UV-vis irradiation with Degussa TiO2 P25 as reference. The prepared BiOBr catalysts were of pure tetragonal phase and its band gap energy was calculated to be about 2.64 eV. Comparing with P25, BiOBr showed promoted photocatalytic activity under UV-vis irradiation, during which more than 90% of toluene was eliminated after 5 h irradiation. Kinetic analysis further demonstrated the enhanced activity of BiOBr under UV-vis irradiation and the reaction rate constant k of BiOBr was nearly 2 times higher than that of P25. The superior activity of BiOBr under UV-vis irradiation can be attributed to its hierarchical structure and suitable band gap energy. Moreover, the reacted intermediates under different light source were identified by GC-MS. Fifteen main intermediates were identified and a tentative pathway of toluene degradation by BiOBr was proposed.