| Oxide morphology had significant eff-ects on the catalytic activity of the catalyst.Catalytic oxidation of HCHO was used as the model reaction to study the catalytic performance of MnCo mixed oxide with different morphologies and Pt/CeO2 catalysts with different CeO2 morphologies.MnCo mixed metal oxide catalyst with line morphology prepared by the hydrothermal method is active for the oxidation of HCHO.This catalyst is of manganese oxide structure of cryptomelaneand,high specific surface area and low temperature reduction activity.The activity of the catalyst is closely related to the doping amount of Co,and the catalyst with Mn/Co ratio of 4:1 showed the highest catalytic activity.800 ppm formaldehyde can be completely oxidized at 120℃ over this catalyst.The synergistic effect between Mn and Co species led to improved redox property of the catalyst,thereby enhancing the catalytic activity of the catalyst for the oxidation of HCHO.The effect of the morphology of CeO2 on the activity Pt/CeO2 catalyst was also investigated for the catalytic oxidation of HCHO.Three different morphologies(nano-sphere,nano-cube and nano-wires)CeO2 were prepared and used as the support of noble metal Pt.Pt/CeO2 was prepared by the sodium borohydride reduction method.It was found that CeO2 with three different morphologies is of the same fluorite type structure,but the special hole structure and larger specific surface area of CeO2 nano-sphere resulted in more metalic Pt and more surface adsorbed oxygen,both of which contributed to improving the catalytic activity for the oxidation of HCHO.HCHO can be totally oxidized at 50℃ over Pt supported on CeO2 nano-sphere catalyst.The above research showed that the different morphologies of metal oxides,with different specific surface area,active sites,adsorption oxygen species and redox ability,exerted significant effect on the performance of the catalyst for the catalytic oxidation of HCHO. |
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