Investigation of the nature of silver species on different Ag-containing NOx reduction catalysts: On the effect of the support

Silver species present in four different Ag-based catalysts, with different supports (Al2O3, ceria–zirconia, sulphated ceria–zirconia and MFI zeolite), were identified by a combination of different characterization techniques (Powder XRD, Raman Spectroscopy, TEM, H2-TPR, DRS UV–Vis Spectroscopy, CO adsorption followed by DRIFTS and pyridine adsorption followed by FTIR), each one allowing to obtain information on specific Ag species. While Powder XRD and Raman gave structural information on the Ag species present on the catalysts, complementary information on their relative reducibility and electronic state was obtained by H2-TPR, DRS UV–Vis and CO adsorption followed by DRIFTS. The possibility of different redox cycles occurring during the NOx SCR reaction between the silver species present in each catalyst was discussed.