Non-thermal plasma assisted preparation of MnCeOx, MnOx and CeO2 catalysts for enhancement of surface active oxygen and no oxidation activity

Abstract

Non-thermal plasma was used to enhance the synthesis of nanostructured manganese oxide, cerium oxides and MnCeOx composite oxide catalysts via the decomposition of organics and nitrates in an integrated network gel. Pure oxides prepared with plasma formed larger crystallites and exhibited more crystallization. The active oxygen species in the plasma were adsorbed through interaction with ions on the catalyst surface; compared to calcined catalysts, the percentage of active oxygen was 33%, 7% and 20% higher for the plasma-treated MnOx, CeO2 and MnCeOx, respectively. The percentage of unsaturated Ce3+ was also 10% higher on the plasma-treated MnCeOx. Furthermore, the NO oxidation efficiency at 275°C for plasma-treated MnOx and MnCeOx was 28% and 21% higher, respectively, than for their calcined counterparts. Due to the lack of significant thermal effects during preparation, the plasma-treated catalysts better retained the structures of their precursors, the even mixtures of manganese oxides and ceria in gel. Additionally, the plasma-treated MnOx and MnCeOx displayed higher formation and decomposition rates for nitrates. The continuous and rapid transformation of NO into nitrates and of nitrates into NO2 contributes to the excellent oxidation efficiency of these catalysts.