Heterogeneous Surface Reaction Analysis of Non-Thermal Plasma-Enhanced Spherical MOx/(Ce0.7Ti0.3)O2 Catalyst Desulfurization: Effects of Plasma and MOx Loading on Surface Oxygen Defects

Abstract

Homogeneous gas-phase plasma reactions and heterogeneous surface reactions are involved in non-thermal plasma-enhanced catalysis, along with a very complicated strengthening mechanism. In this study, we supported CuO, Co3O4, Fe2O3, or NiO on a hydrothermally synthesized spherical (Ce0.7Ti0.3)O2 catalyst, analyzed its active sites, and examined how plasma affects the catalyst surface and influences heterogeneous surface reactions. Loading CuO onto the catalyst led to increases of 5.85 and 13.51% in the proportions of surface Ce3+ and surface O vacancies, respectively. The CuO-loaded catalyst exhibited a significantly higher redox capacity than the other catalysts at 250–290 °C, which promotes SO2 desorption and surface reactions at low temperatures. Treatment with plasma led to increases in the active-to-lattice-oxygen ratio on the catalyst surface (by 19.12%), the defect-induced D-band to F2g band (ID/IF2g) ratio (by 0.443), and the D-band intensity (by a factor of 3.5). Significantly more defects that adsorb plasma-generated oxygen radicals (O* and O2*) and O3, which subsequently oxidize adsorbed pollutant molecules, are present on the catalyst surface. In general, the special surface properties of the spherical CuO/(Ce0.7Ti0.3)O2 catalyst are applicable to a broad number of non-thermal plasma-enhanced catalytic oxidation scenarios.