Modulation Morphology On Metal Oxides By Chemical Etching And Its Photodegradation Performance Research

With the rapid development of industry in the world,it has brought great convenience to human beings,but the resulting environmental pollution has seriously affected people’s production and life.Among them,water pollution is one of the main concerns of the society.The pollutants mainly include organic dyes discharged from textile factories,antibiotics abused by the medical industry,and waste liquids discharged from factories.Organic pollutants are difficult to be completely eliminated by traditional processes,and new green photocatalytic degradation technologies are required.Metal oxide semiconductors are commonly used catalysts for photocatalytic degradation.They have the characteristics of stable structure and tunable morphology.During the photodegradation process,they can be excited by photons with sufficient energy to generate photogenerated carriers.Radicals generated by photogenerated carriers are the main active species in the photocatalytic process.Therefore,in order to improve the utilization rate of metal oxide carriers,the surface morphology of metal oxides can be modulated by chemical etching,and a hierarchical structure can be constructed on the crystal surface to prepare catalysts with the best photocatalytic performance.Based on this,this paper mainly focuses on the following three aspects:（1）The morphology of transition metal oxide iron oxide（α-Fe₂O₃）was modulated to improve its photodegradation performance of Rhodamine B.The symmetric hexagonal bipyramidα-Fe₂O₃was synthesized by hydrothermal method,And explore the optimal synthesis reaction conditions ofα-Fe₂O₃symmetrical structure and observe the growth process of crystal from FeOOH toα-Fe₂O₃Based on the chemical etching method to adjust the crystal morphology,oxalic acid was used to etch the symmetrical hexagonal bipyramid,the regular symmetrical crystal structure was changed into an asymmetrical hexagonal pyramidal structure,and the etching mechanism was explored.The degradation effect of the hexagonal pyramid was not expected,but the morphology evolution process of the asymmetric structure has certain reference significance for exploring the chemical etching of crystals.（2）The morphology of rare earth oxide cerium oxide（CeO₂）was modulated to improve its photocatalytic performance of ciprofloxacin.Octahedral CeO₂was synthesized by hydrothermal method,and the changes of CeO₂crystal morphology were observed by scanning electron microscope（SEM）.After that,the octahedral CeO₂was chemically etched by introducing hydrogen peroxide and nitric acid.The morphology changes of the octahedral etching process were observed by SEM,and the etching conditions were optimized to produce a uniform porous structure on the surface.Using the color reaction,it can be concluded that the reductive dissolution of cerium oxide in hydrogen peroxide and nitric acid solution occurs.The photodegradation performance of the samples before and after etching was evaluated,and the etched samples showed better degradation activity than the parent crystal.Among them,the samples with photolithography for 1 h had the best performance,and the surface porous structure had a positive effect on the photocatalytic performance.（3）The morphology of the composite metal oxide zinc ferrite（ZnFe₂O₄）was modulated to explore the effect of morphology on the photocatalytic performance of methylene blue.The octahedral ZnFe₂O₄was synthesized by hydrothermal method,and the optimal conditions for the synthesis of octahedral crystals were investigated by single factor experiments.Hydrochloric acid was used to etch the ZnFe₂O₄parent crystal.According to the SEM characterization results,the samples obtained under different etching time conditions showed different etching degrees.Comparing the photodegradation MB performance of the samples before and after etching,the sample etched for 24h has the best activity,and the degradation rate is 1.4 times that of the parent crystal.The etched sample still retains the magnetic properties and is easy to recover..