CO₂/CH₄ Glow Discharge Plasma. Part II: Study of Plasma Catalysis Interaction Mechanisms on CeO₂

In situ FTIR transmission experiments for CO₂ and CO₂–CH₄ plasma were performed for a fundamental study of surface plasma interaction with cerium oxide (CeO₂) as catalytic surface. Utilizing a DC glow discharge plasma reactor at low pressure, it was observed that CO₂ gas adsorbs in the surface forming tridentate carbonates and hydrogen carbonates. When CO₂–CH₄ plasma is ignited, formate species were formed while carbonate species disappeared from the surface. The CeO₂ pellet has also been placed downstream the plasma in order to observe the role of the gas composition at the exit of CO₂–CH₄ plasma on CeO₂ without any heating or strong electric field. In addition, the effect of water was investigated in several surface phenomena. OH groups play an important role in the reaction with tridentate carbonates to generate formates under plasma. The gas phase chemistry of the CO₂–CH₄ plasma used here has been described in details in the part I of this work. The conclusions drawn on the gas phase contribute to the understanding of the observed phenomena on CeO₂. These results enlighten the complex mechanisms occurring during CO₂–CH₄ plasma reactions on surfaces that could help in the improvement of CO₂ recycling.