Synergistic Effect Of Copper-cerium Catalysts Promoted By Reduced Graphene Oxide On Catalytic Performance For Preferential CO Oxidation

The development of modern industrial technology provides an unprecedented high quality of life for us,but the severe environmental pollution and frequent energy crisis cast a lingering shadow.Hydrogen as a renewable clean energy source has got much attention,especially in the form of proton exchange membrane fuel cells(PEMFCs).However,the industrial hydrogen,which was produced by reforming hydrocarbons and water-gas shift reactions,still typically contains significant quantities of CO(1%).This amount of unconverted CO could poison the current anode materials,which must be removed below 10 ppm for hydrogen fuel-cell applications.The preferential oxidation of carbon monoxide(CO-PROX)has been considered as the most effective and straightforward method to eliminate CO in excess hydrogen.Although traditional copper-cerium catalysts have a good catalytic activity and wide total CO conversion window at the high temperature,they present a poor performance of CO oxidation at the low temperature due to its small specific surface area and low concentration of oxygen vacancies.Graphene with the two-dimensional lamellar structure has the advantages of high mechanical strength,good electrical and thermal conductivity,large specific surface area and excellent reduction ability and so on.Therefore,we except to develop the strategy of introducing graphene in copper-cerium oxides to obtain nano-composite catalysts with the better catalytic performance at the low temperature.The main contents of the work are as follows:A series of the RGO/CuxO-CeO2,RGO/CuxO and RGO/CeO2 nano-composite catalysts with the different copper/cerium molar ratio and the structure of sheet-on-sheet were synthesized by a facile hydrothermal procedure.It is found that there is a large amount of reduced copper species in the RGO/CuxO-CeO2 catalysts.The spherical nanoparticles of copper species can be served as spacers to prevent the stacking of RGO.Moreover,RGO/CuxO-CeO2-B catalyst has a good resistance to H2O and CO2.The RGO/MWCNTs/CuXO-CeO2 catalysts with the structure of three-dimensional framework were synthesized by the precipitation and hydrothermal method,respectively.It is found that the introduction of RGO and MWCNTs improves the dispersion,reduction ability of CuxO and CeO2 and enhances the concentration of oxygen vacancies.However,the excessive reduction of copper species has a negative impact on catalytic performance at higher temperature.A series of RGO/CuxO-CeO2 nano-composite catalysts with different copper-cerium mole ratio and the structure of CeO2 nanorod were prepared by hydrothermal method.It is found that CeO2 nanorods can effectively prevent the reunion of graphene when Cu/Ce mole ratio is 3:7,and the RGO/CuxO-CeO2-A catalyst has the largest surface area and the best catalytic performance for the CO-PROX reaction compared with other catalysts.