Effects of precursors on the surface Mn species and the activities for NO reduction over MnOx/TiO2 catalysts

TiO2-supported manganese oxide catalysts were prepared from two different precursors, manganese nitrate (MN) and manganese acetate (MA), and these samples were characterized by BET, XRD, TG/DTA, XPS and FT–IR. The characterization results showed that the MN precursor resulted primarily in MnO2, accompanied with some Mn-nitrate, while the MA precursor caused mainly Mn2O3 species. These two different precursors also led to different surface Mn atom concentrations indicated by XPS and NH3 adsorption. Consequently, the higher low-temperature activity of MnOx/TiO2 from MA precursor was attributed to higher surface Mn concentration and the surface Mn2O3 species.