Catalytic combustion of CO over Cu-doped iron oxides: CO2 effects on activity

Abstract

This study reports the catalytic combustion application of FeCuOx thin films synthesized through a doping strategy with different Fe/Cu molar ratios via one-step synthesis route. Structure analysis of the as-prepared thin film reveals the formation of single-phase delafossite structure. A smooth hollows film surface with agglomerated grains was observed. With the introduction of Cu content, Cu+ was successfully embedded in Fe2O3 lattice to form substituted structure, whereas the ratio of OLatt/OAds tended to increase. The perceived behavior was ascribed to the progressive incorporation of Cu, which brought structural changes favoring the formation of anionic vacancies and the mobility of oxygen. The catalytic activity was investigated through the complete catalytic combustion of CO with a high GHSV of 184,500 mL·g−1·h−1, which is closer to actual engineering for the commercial application of the catalytic combustion. The addition of higher quantity of Cu transferred the conversion curvature toward lower temperatures, due to active Cu, Fe and surface oxygen species. Moreover, the effects of CO2 interaction on the reaction mixture was analyzed in order to assess the performance of thin film catalysts under realistic conditions of reaction. Although the principal inhibitor effect was associated with the CO2, the progressive introduction of CO2 in the reaction, gave rise to a decrease of the CO conversion. Furthermore, theoretical calculations based on DFT method of CO with CO2 oxidation over CuFeO2 delafossite film surface catalyst demonstrated that the existence of CO2 acted as an inhibitor in the CO adsorption process which led the reaction to higher temperature.