Plasma-catalytic conversion of CO2 to CO over binary metal oxide catalysts at low temperatures

Abstract

Non-thermal plasma (NTP) technology is gaining increasing interest for CO2 conversion due to its potential to convert inert and stable CO2 to value-added fuels and chemicals at ambient conditions. Combining catalysts with plasma can enhance conversion and energy efficiency simultaneously, overcoming the trade-off barrier commonly present in plasma processes. This work reports the influence of various ceria-promoted iron oxide catalysts on the decomposition of CO2 to carbon monoxide and oxygen in a packed bed, dielectric barrier discharge (DBD) reactor at low temperatures and ambient pressure. As ceria is an expensive rare earth metal, its combination with a cheap, abundant metal such as iron can make the process far more economical. The optimum CO2 conversion (24.5%) and energy efficiency (13.6%) were achieved using γ-Al2O3 supported 5Fe5Ce, almost twice the conversion attained using 10Fe (13.3%). Catalysts were characterized using N2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, H2-temperature programmed reduction (H2-TPR), X-ray photoelectron spectroscopy (XPS) and X-ray absorption near edge structure (XANES) analysis. A solid solution formed from the mixture of iron oxide and ceria. A critical concentration of iron oxide is required to increase the number of oxygen vacancy sites in the solid solution. The synergy between Fe and Ce, and thus the oxygen vacancy sites, can also be optimized via the synthesis method. A reaction mechanism has been proposed for CO2 conversion at the catalyst surfaces.