Surface Morphology Control Of SmMn₂O₅ Nanocrystals And Catalytic Performance For NO Oxidation

It is great significant to oxidize NO to NO₂ for NO_x removal in diesel vehicle.Mullite SmMn₂O₅ oxide has been reported to be a promising catalyst for NO oxidation.However,the effect of size and surface morphology of SmMn₂O₅ on NO oxidation performance remains unclear.In this paper,the orthorhombic SmMn₂O₅ nanocrystals are successfully synthesized through a simple and tunable hydrothermal route.Three typical size and morphologies of the SmMn₂O₅ nanocrystals are chosen to further investigate the relationship between surface morphology and NO catalytic oxidation.The composite materials are synthesized on the basis of rare earth manganese oxide.This work not only explores the different between the composite materials and pure SmMn₂O₅ for NO catalytic oxidation,but also provides experimental reference for further commercial application.The main works are as follows:Firstly,a control variable method is adopted to synthesize SmMn₂O₅ nanocrystals via changing the condition of the reaction temperature,the reaction time and the pH value of the precursor solution.Among them,the nanoparticles exhibit a better catalytic activity for NO oxidation than the nanorods,as it can efficiently convert NO at the rang of 200°C-300°C.This result due to the nanoparticles are more helpful to surface oxygen adsorption,and nanoparticles have more?020?crystal planes been exposured which include Mn⁴⁺-Mn⁴⁺active sites.This work paves a new way for the crystal planes modification of SmMn₂O₅nanocrystals as NO oxidation catalyst to achieve an enhanced performance for environmental applications.Secondly,this thesis explores the different between three composite materials and pure SmMn₂O₅ for NO catalytic oxidation by carbon nanotubes,graphene oxide,carbon quantum dots as the carriers.Among them,SmMn₂O₅/CNTs composite materials can reduce T_50%.This result due to the thermal conductivity of the carbon nanotubes is superior and SmMn₂O₅/CNTs composites are more advantageous to the surface oxygen activation.Finally,this thesis explores the different between composite materials of cerium oxide content and pure SmMn₂O₅ for NO catalytic oxidation by CeO₂ nanoparticles as the promoter.Among them,SmMn₂O₅-0.005MCeO₂ composites have better catalytic activity.This result due to composite materials of oxygen storage capacity increase at the same time does not reduce the active component.