Study of plasma-surface interactions of CO2-CH4 plasma on CeO2 using in situ Infrared Transmission experiments *

Increase in global temperature is mainly attributed to the greenhouse gas effect specially from carbon dioxide (CO2) and methane (CH4) emissions. Dry reforming of methane (DRM) is one the processes proposed for CO2 utilization leading to the conversion into valuable chemicals. Non-thermal plasmas (NTP) can provide the highly energetic environment needed for CO2 conversion. However, a plasma-catalysis approach could offer a significant advantage by improving conversion, selectivity and energy efficiency. Further development and optimization can be expected through greater understanding of the underlying mechanisms on a catalytic surface. In this study, we present evidence of the plasma-surface interaction of the intermediates present in CeO2 by in situ IR transmission experiments using low pressure glow discharge plasma reactor. Experimental results show the adsorption of CO2 as carbonates at room temperature further reacting with H active species generating formates under plasma conditions. Evolution of formates species is followed as function of time. Evidence of derivates of methane decomposition is observed on the surface. The CeO2 pellets used were subsequently characterized by X-Ray Diffraction (XRD), Diffuse Reflectance infrared Fourier transformed spectroscopy (DRIFTS) and Thermal Programmed Desorption (TPD) exhibiting a change in the oxidation state of ceria ions. The plasma-catalyst interactions were investigated under different concentrations and varying configurations: plasma in situ and downstream gas from plasma reaction. The elucidation of adsorbed intermediates of DRM reaction is crucial in the understanding of the mechanistic insight in CO2 conversion by plasma catalysis.