Revealing the differences in CO oxidation activity of Fe-CeO2, Fe2O3, and CeO2 using operando CO2-DRIFTS-MS: Carbonate species and desorption process

The carbonate on the catalyst surface is the key factor limiting carbon monoxide (CO) oxidation activity. However, the relationship between different carbonate species and surface oxygen species is not clear. In this paper, Fe-CeO2, Fe2O3, and CeO2 catalysts prepared by aerosol method are selected as the research target, and operando DRIFTS-MS is used as the main characterization method. Fe-CeO2 has good redox properties resulting in the best CO oxidation activity (350 degrees C) and CO2 selectivity (98 %). Operando DRIFTS-MS results indicate that surface M=O species play a crucial role in the catalyst's activity, demonstrating the ability to react with CO at low temperatures. Notably, a high concentration of M=O facilitates the formation of monodentate carbonate (vas(CO32- )) (vas(CO32- ) decomposes at 100 degrees C). With increasing temperature, Ce--O and M-O-Ce also react with CO and produce M-Ov-Ce (oxygen vacancy). CO adsorption on M2+-O22- or M sites to form vas(OCO) or vs(OCO). The decomposition temperature of vs(OCO) exceeds that of vas(CO32- ) significantly, and its presence serves as the crucial step in the oxidation of CO. The above conclusions reveal the relationship between surface carbonate and oxygen, and provide a theoretical basis for regulating the surface structure of catalysts.