Enhanced plasma-catalytic decomposition of toluene over Co–Ce binary metal oxide catalysts with high energy efficiency

Abstract

In-plasma catalysis has been considered as a promising technology to degrade volatile organic compounds. Heterogeneous catalysts, especially binary metal oxide catalysts, play an important role in further advancing the catalytic performance of in-plasma catalysis. This work investigates the toluene decomposition performance over Co–Ce binary metal oxide catalysts within the in-plasma catalysis. Co–Ce catalysts with different Co/Ce molar ratios are synthesized by a citric acid method. Results show that the catalytic activity of Co–Ce catalysts is obviously superior to those of monometallic counterparts. Especially, Co_0.75Ce_0.25O_x catalyst simultaneously realizes highly efficient toluene conversion (with a decomposition efficiency of 98.5% and a carbon balance of 97.8%) and a large energy efficiency of 7.12 g kW h⁻¹, among the best performance in the state-of-art literature (0.42 to 6.11 g kW h⁻¹). The superior catalytic performance is further interpreted by the synergistic effect between Co and Ce species and the significant plasma–catalyst interaction. Specifically, the synergistic effect can decrease the catalyst crystallite size, enlarge the specific surface area and improve the amount of oxygen vacancies/mobility, providing more active sites for the adsorption of surface active oxygen species. Meanwhile, the plasma–catalyst interaction is able to generate the surface discharge and reinforce the electric field strength, thereby accelerating the plasma-catalytic reactions. In the end, the plasma-catalytic reaction mechanism and pathways of toluene conversion are demonstrated.