Investigating the differences of active oxygen species and carbonate species on the surface of Ce0.95M (M = Mn and Zr)0.05O2−δ catalysts prepared by the aerosol method during CO oxidation using operando TPR-DRIFTS-MS†

Abstract

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−δ catalysts are selected as the research target and operando 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−δ catalyst has the best CO conversion (145 °C) and CO₂ selectivity (99%). Operando DRIFTS-MS results show that MO plays a key role on the catalyst surface and can react with CO at low temperatures. Importantly, the high content of MO is conducive to the formation of monodentate carbonate (M–O–CO₂) (M–O–CO₂ decomposes at 50 °C). As the temperature increases, CeO 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⁺–O₂²⁻) 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.