Regulation Of Ceria Based Oxides Surface Oxygen Vacancies And The Catalytic Performance For Diesel Soot Oxidation

Diesel engine has become the main driving force of motor vehicles because of its high thermal efficiency,low fuel consumption and wide power coverage.However,soot emission is one of the important factors that restrict the development and application of diesel engine,and it is also one of the main culprits of air pollution.The results show that the CeO₂ catalyst exhibits good catalytic activity for soot particles and it is one of the most promising catalysts for the future replacement of noble metal catalysts.The catalytic activity of Ce based catalysts is related to the oxygen vacancies in the CeO₂lattice,we investigate the catalytic properties of CeO₂ from the following two aspects:?1?We used laser etching and NaBH₄ hydrothermal reduction to improve concentration of surface oxygen vacancies of CeO₂,the influences of preparation process on the microstructure of CeO₂ and influences of catalytic activity in the oxidation of the soot particles,and the micro reaction mechanism is discussed.?2?Ag/CeO₂ and Fe₂O₃/CeO₂ sample were prepared by laser etching and sol-gelmethod,the phase structure,surface morphology,surface micro structure,pore structure and the carbon particle catalytic activity and other aspects of the material characterization were researched,the effecting of material structure on the catalytic activity has been researched.The physicochemical properties and catalytic activity of the catalysts were characterized by means of XRD,SEM,TEM,XPS,H₂-TPR,BET and the following conclusions were obtained by analysis and comparison:?1?Laser etching and NaBH₄ hydrothermal reduction does not affect the crystal structure of CeO₂;XPS analysis shows that the surface oxygen concentration has been greatly improved;catalytic performance of CeO₂ for soot oxidation has been greatly improved after laser etching and NaBH₄ hydrothermal reduction treatment;NaBH₄hydrothermal reduction CeO₂ with more Ce³⁺,which has more active oxygen and better catalytic activity?2?We found that both Ag/CeO₂ and Fe₂O₃/CeO₂ were synthesized by sol-gel method and laser method.The catalytic activity of the catalyst has been greatly improved through TEM and XRD analysis by introducing Ag and Fe2O3.The characteristic temperature Tm in the TG test has been greatly reduced,the specific surface area has increased,and the surface adsorption sample of the sample has been greatly improved.Compared with pure ceria,Ag/CeO₂ and Fe₂O₃/CeO₂ samples have larger specific surface area and better catalytic performance.In the process of the catalytic soot,the process can be divided into three steps:first,the oxygen vacancy adsorbed oxygen atom to transform reactive oxygen,and active oxygen then transfer onto the surface of the catalyst,Last but not least,the active oxygen and soot oxidation.The concentration of oxygen vacancies plays a decisive role in the catalytic process of Fe₂O₃/CeO₂.At the same time,the transport of reactive oxygen species plays a decisive role in the Ag/CeO₂system.By comparison,the catalytic activity of 1:1 Ag/CeO₂ etched by laser is the best among all samples.