The Preparation Of Ceria Nanomaterials And Their Cataclytic Performance For CO Oxidation

With the rapid increase in the number of cars,CO in automobile exhaust has become one of the sources of air pollution.CO not only endangers human health,but also has a far-reaching impact on the environment.At present,the best solution is using catalysts to oxidize toxic CO into non-toxic CO2.Ceria has been widely used in CO catalytic oxidation due to its unique electronic structure and oxygen storage/release property.As people pay more attention on health and environmental protection,traditional ceria nanomaterials are difficult to meet the practical application requirement.At present,there are two common strategies to enhance the catalytic activity of ceria:?1?modify ceria with noble metals or transition metals;?2?control morphology of ceria to expose more active crystal planes.Based on the above strategies,this paper mainly does the following three research work:1.Modification of amino functional groups of CeO₂ nanorods and preparation of Pd/CeO₂ nanocatalystsIn order to improve the catalytic activity of ceria,palladium was selected to modify it.CeO₂ nanorods were choosed as the support,because the oxygen vacancy formation energy on?110?surface is the lowest,and it has a stabilizing effect on metals.However,the agglomeration of nanorods prepared by traditional hydrothermal method is serious,so the first step is to improve the dispersion of ceria nanorods.Dopamine hydrochloride was selected to modify nanorods with amino groups.When hydrochloric acid was added,amino group was changed into-NH3 + cation.The surface of ceria was positively charged and remained monodisperse due to electrostatic repulsion in aqueous solution.Using ionized nanorods as support,Pd/CeO₂ nanocatalysts with high catalytic activity were successfully prepared through the amino reduction of palladium acetate.2.Modification of carboxyl functional groups of CeO₂ nanorods and preparation of Cu/CeO₂ nanocatalysts and Pd?Cu/CeO₂ nanocatalystsCeO₂ nanorods were modified by 3,4-DHCA to carry carboxyl groups.After adding NaOH,the carboxyl group was changed into-COO-anion.The surface of ceria nanorods was negatively charged,and remained monodisperse due to electrostatic repulsion in aqueous solution.The ionzed nanorods were used as substrates to form stable complexes with copper by using the chelating ability of carboxyl groups.It is noteworthy that the copper species located on the surface are in the form of super-small copper nanoclusters,which greatly improves the catalytic activity.In addition,copper ions on the surface of Cu/CeO₂ can be used as adsorption sites to attract PdCl42-anions,thus realizing the co-loading of copper and palladium bimetals.The new Pd-Cu/CeO₂ catalyst not only has excellent catalytic effect,but also has good cyclic stability.3.Preparation of Fe-Ce solid solutions with different morphologies and the effect of doping species on the crystal plane effectFe-Ce solid solution with nanorod morphology and nanocube morphology was successfully prepared by traditional hydrothermal method.For pure ceria,the catalytic activity of nanorods is higher than that of nanocubes.However,when iron ions were doped into ceria lattice,the catalytic activity of nanocube exceeded that of nanorod after oxygen activation.This is because the?100?crystal surface exposed by ceria nanocube has higher surface energy.In the process of oxygen calcination,partial lattice iron ions migrate to the surface to form more active adsorption sites,which accelerates the catalytic reaction process.The study about crystal plane effect of Ce-based composite nanomaterials provides more possibilities to design excellent catalysts.