Self-assembled Multi-structured Bismuth Oxyhalides Micro/nano Materials And Their Photocatalytic Activity Properties

Uniform and monodispersed BiOCl, I-BiOCl, and BiOMxN1-x（M, N=Cl, Br, I）microspheres with different surface structures and performance have been first timefabricated using one-step approach under atmospheric pressure. With only changingthe molars ratio of X–（X–=Cl–, Br–, I–） and the concentration of citric acid and PVP inthe reaction system, the controllable shapes and band structure of BiOCl, I-BiOCl,and BiOM_xN_1-x（M, N=Cl, Br, I） with different compositions could be prepared, suchas nanoplates, hollow, nestlike, core-shell, and solid microspheres. The morphology,structure, chemical composition, and performance characteristics of the3Dhierarchitectures （HAs） of BiOCl, I-BiOCl, and BiOM_xN_1-x（M, N=Cl, Br, I） werecharacterized by XRD, FESEM, TEM, EDS, XPS, UV–vis spectra, nitrogensorption/desorption, PL spectra and photocatalyst reaction. The detail results aresummarized as follows.Bismuth oxychloride （BiOCl） submicrocrystals with tunable morphologies fromnanoflakes to hollow microspheres （HMSs） have been synthesized by hydrolyzing ahierarchical precursor （BiCl₃） in the solution of water and ethanol with adding of PVPand citric acid. The obtained BiOCl possessed submicrocrystals from single crystalsto polycrystals. The crystal growth, morphology and formation of the nestlike andhollow structure were induced by citric acid and PVP. The photocatalytic activities of3D hierarchical hollow microspheres show the highest photocatalytic activity by thedegradation of Rhodamine-B dye under ultraviolet light irradiation.Iodine-incorporated BiOCl core-shell microspheres were first time fabricatedusing one-step approach under atmospheric pressure. In the reaction system, iodine anions were utilized both as structure directing agents for fabricating hollow,core-shell, solid structure and doped ions incorporated in the framework of the BiOClcore-shell spheres to extend the light adsorption edge to visible light region. I-BiOClwithout adding PVP was also researched, this result demonstrated that the formationof the core-shell structure is induced by a synergetic effect by iodine and PVP. Theas-prepared I-BiOCl core-shell microspheres showed much higher photocatalyticactivity than that of the reported TiO₂-x-yN_xF_y（SC）-3and Bi2WO6, which wasevaluated by the degradation of phenol under visible light （λ>420nm） andRhodamine-B under visible light （λ>420nm） and sun light irradiation.The controllable shapes and band structure of BiOMxN1-x（M, N=Cl, Br, I） withdifferent compositions were first fabricated using one-step approach by hydrolyzing aprecursor （Bi（NO3）3） in the solution of water with adding different molars ratio ofX–（X–=Cl–, Br–, I–） under atmospheric pressure. All of the obtained BiOM_xN_1-xsamples were three-dimensional （3D） microspheres self-assembled by nanoplates. Thesamples with different x values exhibited different surface structures constitution andcomposition-dependent absorption properties in the UV and visible light region.Meanwhile, both PVP and citric acid play important role in the formation of theBiOM_xN_1-xhollow and solid microstructure. All the as-prepared BiOM_xN_1-x（M, N=Cl,Br, I） compound exhibited much higher photocatalytic activity for the degradation ofRhodamine-B （RhB） dye under visible-light irradiation than pure ones （BiOX （X=Cl,Br, I））. Specially, the3D hierarchical BiOM_xN_1-x（M, N=Cl, Br, I） hollowmicrospheres （HMSs） compounds show the highest catalytic performance because ofthe synergetic effect, including higher surface area, porous structure, enhancement oflight absorbance and the lower the recombination of photo-induced electron-holepairs.