Design And Preparation Based On Transition Metal Oxide Core-shell Structure And Its Research In The Field Of Catalysis

Metal oxide is an important kind of catalysts.Compared with single-component metal oxides,mixed metal oxide catalysts have better catalytic potential,which can improve the catalytic efficiency because of the synergistic effect between metal oxide active species.In this thesis,single-component and mixed metal oxide particles as well as core-shell structrured particles were prepared for the catalytic reduction of dyes and the catalytic oxidation of toluene gas.The effect of synergistic effect between metals on catalytic activity was studied and the possible reaction mechanism was discussed.The main research contents and results are as follows:By using Cu₂O cubes as templates,single-component and mixed metal oxide particle catalysts were prepared in the presence of soft alkali sodium thiosulfate and metal ions through in situ etching and precipitation.Their catalytic reduction performances toward p-nitrophenol and various dyes in the presence of sodium borohydride were studied.The results show that the one-component Mn₃O₄ catalyst exhibits excellent catalytic performance in the catalytic reduction of various dyes.The two-component catalyst Mn₃O₄/NiO,beneficial from the synergistic effect between metal oxide active species,exhibits better catalytic activity compared with the one-component catalyst in the process of catalytic reduction of p-nitrophenol,and the Mn₃O₄/NiO catalyst showed excellent stability in recycling experiments.Core-shell structured CuO@m SiO₂ was synthesized by coating a layer of mesoporous silica on the surface of Cu₂O cubes.The existence of mesoporous silica shells was beneficial to the molecular storage,separation and confinement during the catalytic process,which can improve the catalytic reaction efficiency and improve the stability of the active centers.The simultaneous etching and precipitation reactions took place by adding metal ions and the etchant Na₂S₂O₃ to CuO@m SiO₂.During the process,the core CuO in the mesoporous shell was gradually etched away,and metal hydroxide particles were formed on the surface of the shell.After calcination,CuO@NiO@m SiO₂and NiO@m SiO₂ with NiO nanoparticles on their surfaces were obtained.CuO@NiO@m SiO₂,due to the good synergistic effect between the CuO core and the NiO nanoparticles on the shell that promotes the improvement of the charge transport efficiency,exhibits more excellent catalytic activity in the catalytic reduction of p-nitrophenol and various dyes.CuO@NiO@m SiO₂showed excellent stability in cycling experiments during the catalytic reduction of p-nitrophenol.Ce-Mn bimetals have strong interaction and excellent redox ability.By a hydrothermal method,core-shell structured m Ce O₂@Mn₃O₄ carriers were synthesized through the in situ growth Mn₃O₄ nanosheets on mesoporous Ce O₂ nanorods.Various characterization results demonstrate the presence of more O vacancies in the Mn-modified m Ce O₂@Mn₃O₄ oxide support,which was crucial for enhancing the catalytic activity of the catalyst.The active centers platinum nanoparticles were loaded on the m Ce O₂@Mn₃O₄ by impregnation and reduction to obtain Pt/m Ce O₂@Mn₃O₄ with different Mn and Pt loading contents.The 0.45Pt/m Ce O₂@2.1Mn₃O₄ catalyst with platinum loading of 0.45%and manganese oxide loading of 2.1%exhibited the highest catalytic activity(T₉₅=165℃)for the oxidation of toluene while maintaining the excellent catalytic stability.