Study On Surface Structure Modulation And Photocatalytic Performance Of Bismuth Oxychloride

Aiming to address energy shortages and environmental pollution,researchers have found that the photocatalytic technology has the potential to achieve wastewater purification and energy conversion.The key point to enhance the efficiency of photocatalysis is to explore efficient photocatalytic materials.Among the semiconductor photocatalytic materials,bismuth oxychloride(BiOCl)has become a favored material by virtue of its exceptional layered electronic structure and indirect band gap.Nevertheless,the lack of visible light response and the high photogenerated carriers recombination rate of BiOCl lead to low utilization of sunlight and weak redox properties.Therefore,there is an urgent demand to modify BiOCl according to its characteristics for improving the visible light response and enhancing the photooxidation capacity.In this thesis,in terms of surface atomic structure modulation of BiOCl,surface modification by polyhydroxylated disaccharides molecules accelerates charge transfer and increases surface reactive sites,and the construction of vacancies and the solid solution is employed to expand the light absorption range.To begin with,the surface atomic structure of BiOCl was modified with polyhydroxylated disaccharides(maltose,sucrose and lactose)under stirring conditions at room temperature.The disaccharides not only act as capping agents to regulate the growth of BiOCl and make its morphological dimensions favorable for the photoreaction,but also reconstruct the surface atomic structure of BiOCl.The hydroxyl groups with empty orbitals in the disaccharides molecules will combine with chloride ions containing lone pairs of electrons during the formation of BiOCl to create hydroxyl-rich surface active zones on the surface.Compared to BiOCl fabricated from monosaccharides,alcohols and aqueous solvents,the polyhydroxylated disaccharides modified BiOCl not only showed a dramatic reduction in the recombination rate of photogenerated carriers,but also exhibited a rapid degradation of high concentrations of organic pollutants.In order to improve the response of BiOCl to visible light,iodine ions were introduced to form BiOCl1-xIx solid solution.During the solvothermal process,the hydroxyl groups in the glycerol solvent will bind to the iodine ions and finally form halogen-vacancy BiOCl1-xInsolid solution,as the bond energy of Bi-I is smaller than that of Bi-Cl.The formation of solid solution causes the catalyst to be sensitive to the visible light response.The construction of halogen vacancies enables effective modulation of the surface structure and captures photogenerated electrons,effectively reducing the recombination rate of photogenerated electrons and holes in photochemical reactions.In addition,the halogen-vacancy BiOCl1-xIn exhibited a greatly enhanced capacity for photoreduction of Cr(Ⅵ)and oxidative degradation of phenol under both visible and full spectrum irradiation.At last,to further increase the response range to visible light,the Br atoms were introduced into the BiOCl1-xIn solid solution to replace part of the Cl atoms,and the iodine-vacancy BiO(ClBr)(1-x)/2Ix-n solid solution was constructed by glycerol solvothermal treatment,taking advantage of the difference in bonding energy between Bi-Cl,Bi-Br and Bi-I.In synergistic effect with iodine vacancies and ternary halogen solid solutions,the iodine-vacancy BiO(ClBr)(1-x)/2Ix-n not only possessed a wide range of light absorption but also presented outstanding photooxidation activity.