Effect of support carbon materials on Ag catalysts used for CO oxidation in the presence and absence of H2

Effects of the support carbon materials on Ag-catalyzed CO oxidation at low temperature and CO preferential oxidation (PROX) in the presence of excess hydrogen were studied for the catalyst systems of Ag/AC (activated carbon), Ag/CB (carbon black) and Ag/CNT (carbon nanotube). By comparison, Ag/CNT exhibited a higher CO conversion with high CO2 selectivity, especially pretreated in H2 for 2 h at 300 °C. On the basis of XPS and N2-sorption analysis, the CNT surface gave rise to high extent of the surface defectiveness and thermal-stable oxygen state, which is necessary for the high dispersion of active species. XRD results revealed that the active species Ag partly transfers from surface into CNTs, increasing the interface between the Ag particles and CNTs. Thus, Ag particles can be protected by CNT coating against sintering and supply more adsorption sites.