In-situ Modified The Perovskite Catalyst LaCo_xPt_1-xO₃ For Soot Oxidation

Perovskite oxides is widely applied to soot oxidation due to low cost,high stability and flexible structure.In the present thesis,we study the effect of partial substitution（in B-sites（active sites）of perovskite）on the activity of catalyst for soot oxidation.Besides,the influence of the in-situ modification and the in-situ exsolution is investigated.And the characteristic of all catalysts is studied by SEM,XRD,TEM,XPS,etc.The detail content is as follows:1.In-situ modification is studied in this work on LaCo_1-xPt_xO₃ for soot oxidation.A series of perovskite catalysts LaCo_1-xPt_xO₃（by sol-gel method）are modified with 30%H₂O₂.XRD,TEM,SEM,BET,XPS,Raman,in-situ DRIFTS,H₂-TPR and TGA are used to investigate physicochemical properties of catalysts.TGA results show that all doped catalysts have a lower temperature of soot conversion,especially LaCo_0.94Pt_0.06O₃(T₅₀=437°C).The T₅₀ of the catalyst with modification by H₂O₂solution decreases at least 20°C than doped catalysts.A highly symmetrical structure and an obvious amorphous phenomenon about 3-5nm are observed in the modified catalysts.According to the XPS study,the symmetrical structure benefits to the movement of oxygen vacancy thus catalyst captures more adsorbed oxygen（about95%）.And the amorphous surface could adsorb more oxygen species.In addition,all catalysts show excellent aging resistance performance.The reaction mechanism of catalyst for soot oxidation is presented in the end.2.The LaCo_0.94Pt_0.06O₃ catalyst is exsolved under 5%H₂/Ar in different temperature and the activity of the exsolved catalysts for soot oxidation is investigated.XRD,TEM,SEM,BET,XPS,H₂-TPR and TGA are used to study the physicochemical properties of catalysts.SEM and TEM results indicate that Pt nanoparticles（<10nm）grow homogeneously on the surface of catalyst after in-situ exsolution.And XRD shows that the exsolved catalysts have a high symmetrical structure.TGA results indicate that all exsolved catalysts exhibit the excellent activity,especially the exsolved catalyst at 350°C(T₁₀=338°C,T₅₀=393°C,T₉₀=427°C).According to XPS study,the high symmetrical structure benefits to the mobility of oxygen vacancy and Pt nanoparticles induce that the oxygen vacancy moves to its adjacent situation,resulting in more adsorbed oxygen on the surface of the exsolved catalyst.The mechanism of reaction is presented in the end.