| Automobile exhaust contains a lot of CO,which has become one of the main sources of air pollution.Using catalyst to convert CO into CO2 is a simple and energy-saving way to remove CO.Research indicates that adding cerium oxide(CeO2)can greatly improve the activity and intensity of catalysts,cerium-based composite materials especially CeO2 as support has attracted widespread attention to CO oxidation.Therefore,we synthesized a series of M/CeO2(M = Au,Cu,Co)nano-catalysts,and explored the influence of pretreatment on M-CeO2 interaction and CO catalytic performance.The conclusions are as follows:?1.The preparation of Au/CeO2 nanocatalysts and pretreatment effects on their catalytic performance for CO oxidation.The encapsulated Au/CeO2 hollow composite shows different pretreatment effects on CO oxidation:O2 pretreatment(T100 = 74 ?)>N2 pretreatment(T100=142?)>CO pretreatment(T100=167 ?).Thanks to well confinement of uniform pores of as prepared Ceo2,the size of deposited Au NPs is well controlled,embedded in the pores of Ceo2.Pretreated Au/Ceo2 catalysts process good stability with no obvious deactivation even after 70 h test.A systematic characterization was performed by employing various techniques(XRD,H2-TPR,STEM-EDS,Raman,XPS and in-situ DRIFTS)in order to understand the importance of Au-Ceo2 interaction,which reveals that the o2 pretreatment may results in(a)the migration of lattice oxygen to surface region as well as obviously increased oxygen vacancies in Ceo2;(b)increasing of Au-Ox and Au-Ox-Ce;(c)the creation of electron holes in Ceo2 substrate and electron deficiency of Au NPs as well as strong Au-Ceo2 interaction;(d)more surface bicarbonates and Au?+-CO were produced during CO oxidation.All these features are responsible for an overall enhanced activity of CO oxidation and better durability of the Au/CeO2 hollow composite.2.The preparation of Cu/CeO2 and Co/CeO2 nanocatalysts and their catalytic performance for CO oxidation.By using precipitation-deposition method,the active component CuOx and CoOx were loaded onto the CeO2 nanorods to explore the influence of different Cu and Co contents on CO catalytic performance.After a series of characterization,such as TEM,XRD,H2-TPR)and CO catalytic performance tests,founded that the CuCeO catalyst with best catalytic activity has more CuOx clusters.For CoCeO catalyst,with the increase of Co contents,the catalytic activity increased,but the individual CoOx phase,in order to better research Co-CeO2 interaction,we choose 5CoCeO for subsequent research.3.Pretreatment effects on the morphology and catalytic performance for CO oxidation of Cu/CeO2 and Co/CeO2 nanocatalysts.The effects of a series of representations such as STEM-mapping,H2-TPR,XPS and in-situ DRIFTS on the treatment of nano-catalysts were explained.When CuCeO and CoCeO nano-catalyst were pretreated at the high temperature of flowing O2:(a)the morphology was still the nanorod,the active component CuOx and CoOx were highly dispersed on the carrier surface;(b)the active sites exposed by CuCeO are CuOx and Cu-[Ox]-Ce structure with highly dispersed surface,with high activity,and high activity sites of various active sites exposed by CoCeO.(c)CuCeO produces more Cu+-CO and surface carbonates in CO oxidation process,which is beneficial to the adsorption of CO and desorption of CO2.All these factors contribute to the acceleration of CO oxidation. |
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