Design And Synthesis Of Bismuth Oxychloride Crystal Facet And Its Photocatalytic Performance

Semiconductor photocatalytic technology is favored by researchers because it can effectively solve environmental pollution and energy depletion.Among them,crystal-facet engineering can effectively regulate the growth of different crystal facets and improve the photocatalytic activity,so it has become one of the main research hotspots.At present,there are four reasons for the influence of crystal on the photocatalytic activity:surface atomic structure;surface electronic structure;surface defects and internal electric field.The reason for the different views is that researchers study the problem from a certain perspective that affects photocatalytic activity;in addition,the degree of exposure of the targeted crystal facet is low.Therefore,to explore the source of facet-dependent photocatalytic performance,it is necessary to obtain a crystal facet with a high exposure ratio,and all factors affecting photocatalytic activity should be fully considered.In this paper,the design and synthesis of bismuth oxychloride crystal facet and its photocatalytic properties are studied,The details are as follows:1.The BiOCl microrod exposed?110?crystal facet was synthesized by hydrothermal method using Bi?NO₃?₃·5H₂O and KCl as the materials and sodium citrate as the additive.The optimal synthesis conditions were explored by controlling variables such as reaction time,reaction temperature,and reactant concentration.The possible formation mechanism of microrod was studied based on the growth process.The experimental results show that microrod has stronger ability to reduce high concentration of Cr?VI?than BiOCl nanosheets.In acidic and neutral solutions,30 mg/L Cr?VI?was completely photoreduced in 4 min and 10 min,respectively.The enhanced photoreduction performance is due to the more negative CB position of BiOCl microrod,which enhances the photoelectron reduction ability.This work provides new ideas for the synthesis of high proportions of exposure to specific crystal facets.2.On the basis of the first chapter,the amount of sodium citrate was changed and a new one-dimensional BiOCl layered structure was synthesized.The BiOCl layered structure consists of many small nanosheets,and HRTEM shows that the nanosheets were exposed?001?crystal facet?front?and?110?crystal facet?side?.The size and thickness of the nanosheets increase as the amount of sodium citrate increases,so the ratio of?110?/?001?gradually increases,and the diameter of the layered BiOCl microrods becomes smaller and smaller.The BiOCl layered structure exhibits superior photocatalytic activity than nanosheets.Under sunlight,MO and RhB were completely degraded within 4and 3 min,respectively.The enhanced photocatalytic activity is due to the rapid separation and transfer of photogenerated electron-hole pairs,as well as the large BET surface area.This work provides a viable solution for the design of a layered structure of bismuth oxychloride.3.Polyethylene glycol?PEG?was used as an additive to synthesize BiOCl nanosheets exposed?001?crystal facet,BiOCl nanoring with co-exposed?110?/?001?facets was first synthesized by selectively etching?001?facets of BiOCl nanosheets in acid solution.By changing the etching time,the diameter of the nanorings gradually increases,and the exposure ratio of the side?110?crystal facet also increases.The unique BiOCl nanoring structure exhibits excellent photocatalytic activity.Under sunlight,97%of MO and 100%of RhB were completely degraded in 2 min and 4 min,respectively.The origin of this facet-dependent photocatalytic performance is ascribed to the formation of II-type facet junctions between?001?and?110?facets in BiOCl nanorings.This work is instructive for the design of bismuth oxychloride photocatalysts.4.Ultrathin Bi₁₂O₁₇Cl₂ nanobelts exposed?001?crystal facet were synthesized by hydrothermal method without any surfactant.Salicylic acid and bisphenol A were degraded under sunlight and visible light respectively.Although the results show that the photocatalytic activity of Bi₁₂O₁₇Cl₂ nanobelts is not as good as that of Bi₁₂O₁₇Cl₂nanosheets,we have analyzed through a series of test characterizations.The fundamental reason for the surface-dependent photocatalytic activity is the enhancement of h⁺oxidation ability and the efficient separation efficiency of electron-hole pairs.This work provides an idea for a comprehensive analysis of the underlying causes of photocatalytic activity.