Preparation, Structures And Performance Of Highly-Dispersed CuO-CeO₂Catalysts Used For CO Preferential Oxidation

The application of proton-exchange membrane fuel cells （PEMFC） using N₂asfuel is an important way for clean energy usage. At present, the N₂is mainly comingfrom the reforming of fossil fuels, however, in the reforming products, there is still0.5-2%CO present, which is a serious poison to Pt-based PEMFC anode catalysts. So,it is necessary to purify the CO before the N₂is introduced to fuel cells. Now, COpreferential oxidation （PROX） is considered as one of the most straightforward andcost effective methods to remove CO. The exploration of highly active and highlyselective catalysts for CO PROX is apparently significant. In this thesis, the supportedCuO-CeO₂catalyst （Cu/Cu+Ce=15） was prepared via a novel route calledchemisorption-hydrolysis, and employed for the preferential oxidation of CO inN₂-rich stream. For comparison, several other conventional methods, such asimpreganation, deposition-precipitation and co-precipitation （IM, DP and CP） werealso employed for the synthesis of CuO-CeO₂catalysts. To increase the specificsurface area of the catalysts, surfactant was used for the preparation of the support.The activity, thermal stability and resisting ability to H₂O and CO₂of the catalystswere evaluated. The results show that the catalyst prepared bychemisorption-hydrolysis method exhibits not only much better catalytic activity andselectivity, but also stronger resisting to H₂O and CO₂.The techniques of BET, XRD, N₂-TPR, N₂O chemisorption, in-situ DRIFTS andEXAFS were employed for catalyst characterization. BET results show that thesample CuO-CeO₂（CH） possesses the largest specific surface area, which canimprove the dispersion of Cu on the support, as confirmed by XRD and N₂Ochemisorption results. The stronger interaction between Cu and support was alsoobserved over this sample as indicated by N₂-TPR results. Besides, the highdispersion of Cu species is favorable to CO adsorption and the formation of stableCu+-CO species, effectively preventing dissociative adsorption of N₂. The surface areaof the support and catalyst can be further increased by using surfactant-assistedmethod; as a result, the Cu dispersion, CO adsorption and the interaction betweencopper oxide and ceria were also promoted. Additionally, the resisting ability to H₂Oand CO₂for the optimal catalyst prepared by different methods was evaluated. Although the presence of H₂O and CO₂leads to a decrease in the catalytic activity, thecatalyst with the support synthesized by using surfactant-assisted method stillpossesses the stronger ability of H₂O and CO₂resistance.