Heterogeneous Surface Reaction Analysis of Non-Thermal Plasma-Enhanced Spherical MO_x/(Ce_0.7Ti_0.3)O₂ Catalyst Desulfurization: Effects of Plasma and MO_x 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, Co 3 O 4 , Fe 2 O 3 , or NiO on a hydrothermally synthesized spherical (Ce 0.7 Ti 0.3 )O 2 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 Ce 3+ 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 SO 2 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 F 2g band (I D /I F 2g ) 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 O 2 *) and O 3 , which subsequently oxidize adsorbed pollutant molecules, are present on the catalyst surface. In general, the special surface properties of the spherical CuO/(Ce 0.7 Ti 0.3 )O 2 catalyst are applicable to a broad number of non-thermal plasma-enhanced catalytic oxidation scenarios.