Research On The Construction Of Efficient CO Oxidation Catalyst Based On Precise Control Of CeO₂ Crystal Plane Orientatio

The CO is a toxic and harmful gas,which mainly comes from the emission of vehicle exhaust and the inadequate combustion of fossil fuels.Due to its large emissions,it is considered to be an air pollutant in urgent need of degradation.Currently,catalytic elimination of CO has been proven to be a cost-effective technological tool.Cerium-based materials are considered to be an important CO oxidation catalyst due to their excellent redox properties.The complexity of conventional powder catalyst structures makes it difficult to identify the active site,which poses difficulties in designing highly active CO oxidation catalysts.Therefore,this paper provides a theoretical basis for the design of CO oxidation catalysts by preparing CeO2 and CeO2-based catalysts with controllable exposed crystalline surfaces to investigate the conformational relationship.The main studies in this paper are as follows:1.Octahedral catalysts,cubic catalysts,particulate catalysts,spherical catalysts,and rod catalysts with exposed(111)+(110)crystal faces were synthesised by hydrothermal methods.The effect of the exposed crystalline faces on the catalytic activity was examined.The results show that the difference in catalytic activity do not originate from the specific surface area size,but is closely related to the exposed crystalline faces.The rod catalyst with exposed(111)+(110)crystal faces has excellent oxygen storage and release capacity,which facilitates the generation of surface oxygen vacancies and significantly reduces the apparent activation energy of the CO oxidation reaction by increasing the activation capacity of O2,ultimately increasing the activity of CO catalytic oxidation.2.The origin of the structural sensitivity of CuO loading on CeO2 support was investigated by loading copper on CeO2 support with different morphologies.The results show that catalysts with exposed multi-crystalline surface have higher concentrations of surface defective Ce3+and oxygen vacancies,which promote the redox cycle of Cu2++Ce3+?Cu++Ce4+.Moreover,the Cu(I)Ox species are only formed on the(110)and(100)planes,and thus the redox properties of the catalyst can be manipulated by precisely modulating the CeO2 exposed crystalline planes.3.The dependence of Pt loading on the crystal surface of CeO2 support was investigated by loading Pt on CeO2 support with different morphologies.The results show that 1Pt/CeO2 catalyst has a significant dependence on crystal surface,and only exposing(111)crystal surface is conducive to the existence of a large number of Pt4+species.When Pt4+and Pt2+species exist simultaneously,the concentration of surface defect Ce3+can be effectively increased,which provides a new idea for the design of Pt/CeO2 catalyst system.4.The effect of crystal plane effect of Pd loading on CeO2 support was investigated by loading palladium on CeO2 support with different morphologies.The results show that the content of PdxCe1-xO2-y species is positively correlated with the catalytic activity and that this species is most readily formed in spherical 1Pd/CeO2-S catalysts with exposed(111)+(100)crystal planes.The presence of this active species promotes the formation of surface defects on the catalyst,increases the oxygen vacancy concentration and enhances the metal-support interaction.Thus greatly improving the CO low-temperature catalytic oxidation activity and achieving a 100%CO conversion rate at 70℃.