Insights into the Role of Nanorod-Shaped MnO 2 and CeO 2 in a Plasma Catalysis System for Methanol Oxidation.

Published papers highlight the roles of the catalysts in plasma catalysis systems, and it is essential to provide deep insight into the mechanism of the reaction. In this work, a coaxial dielectric barrier discharge (DBD) reactor packed with γ-MnO 2 and CeO 2 with similar nanorod morphologies and particle sizes was used for methanol oxidation at atmospheric pressure and room temperature. The experimental results showed that both γ-MnO 2 and CeO 2 exhibited good performance in methanol conversion (up to 100%), but the CO 2 selectivity of CeO 2 (up to 59.3%) was much higher than that of γ-MnO 2 (up to 28.6%). Catalyst characterization results indicated that CeO 2 contained more surface-active oxygen species, adsorbed more methanol and utilized more plasma-induced active species than γ-MnO 2 . In addition, in situ Raman spectroscopy and Fourier transform infrared spectroscopy (FT-IR) were applied with a novel in situ cell to reveal the major factors affecting the catalytic performance in methanol oxidation. More reactive oxygen species (O 2 2- , O 2- ) from ozone decomposition were produced on CeO 2 compared with γ-MnO 2 , and less of the intermediate product formate accumulated on the CeO 2 . The combined results showed that CeO 2 was a more effective catalyst than γ-MnO 2 for methanol oxidation in the plasma catalysis system.