Investigating the differences of active oxygen species and carbonate species on the surface of Ce_0.95M (M = Mn and Zr)_0.05O_{2−<i>δ</i>} catalysts prepared by the aerosol method during CO oxidation using <i>operando</i>

Surface oxygen species and carbonate species play an important role in CO oxidation. However, their essential relationsh with CO oxidation activity remains unclear. In this paper, Ce_0.95M (M = Mn and Zr)_0.05O_2-<i>δ</i> catalysts are selected as the research target and <i>operando</i> TPR-DRIFTS-MS is used to investigate the changes of oxygen species and carbonate species on the catalyst surface. The Ce_0.95Mn_0.05O_2-<i>δ</i> catalyst has the best CO conversion (145 °C) and CO₂ selectivity (99%). <i>Operando</i> DRIFTS-MS results show that MO plays a key role on the catalyst surface and can react with CO at low temperatures. Importantly, the high content of MO is conducive to the formation of monodentate carbonate (M-O-CO₂) (M-O-CO₂ decomposes at 50 °C). As the temperature increases, CeO and M-O-Ce also react with CO and produce M-O_v-Ce (oxygen vacancies). CO can combine with O₂ adsorbed on the M-O_v-Ce (M²⁺-O₂^2-) to form bidentate carbonate (M-O₂-CO). The decomposition temperature of M-O₂-CO is much higher than that of M-O-CO₂, and its existence is the decisive step of CO oxidation. The above results provide a new way to regulate the surface oxygen species and carbonate species of Ce based catalysts in the later stages.