Enhanced plasma-catalytic decomposition of ethyl acetate with ordered three-dimensional multi-mesoporous bimetallic cobalt oxides

Plasma-assisted catalysis for efficient and deep decomposition of volatile organic compounds (VOCs) has been a highly discussed topic. A series of Co3O4-based catalysts doped with Mn, Ce, Cu, Ni, and Fe were prepared by templating with KIT-6 for plasma-catalytic decomposition of ethyl acetate (EA). Through sample characterization, these doped catalysts were found to contain ordered mesoporous structures with multilevel pore sizes, which were larger than that of original meso-Co3O4. Metal ion doping increased the proportion of surface Oads + OOH–, redox ability, and specific surface areas, which correspondingly enhanced activity in this plasma-catalytic system. Mn doping increased the specific surface area from 123.61 m2·g−1 for meso-Co3O4 to 342.12 m2·g−1 for Meso-Mn/Co3O4 and increased the Oads + OOH– proportion from 39.10 % for meso-Co3O4 to 53.69 % for Meso-Mn/Co3O4. Accordingly, the EA decomposition efficiency on meso-Mn/Co3O4 was about 30 % higher than on meso-Co3O4 at 350 J/L and 100 °C, and achieved 99.4 % removal efficiency of EA at 750 J/L and 300 °C. Based on density functional theory (DFT) calculations, Mn was confirmed to be preferentially doped into Co3O4 by substitution of Co3+. Mn doping and surface-adsorbed oxygen significantly enhanced EA chemisorption. A reaction mechanism was finally proposed based on the analysis of the reaction intermediates and byproducts. O3 oxidation can effectively remove ethanol, CH3CH2* and CH3* species, while the preposed plasma process is essential for the decomposition of acetic acid, acetaldehyde, formic acid and methanol. This article paves the way for utilization of ordered mesoporous composite metal oxides in plasma-catalytic system for VOCs decomposition.