Abstract
The dynamic structures of a highly disordered manganese oxide catalyst (HDMO) and intermediates were thoroughly studied from precursor to working catalyst. Excellent CO oxidation activity at low temperatures (T50 = 83 °C) was performed over a HDMO in the presence of H2O and CO2. The specific reaction rate of 4.56 μmolCO·gcat−1·s−1 at 90 °C was approximately 25 times and 15 times higher than those of bixbyite-type α-Mn2O3 and cryptomelane-type α-MnO2, respectively. With X-ray photon electron spectroscopy (XPS), we reveal that more surface oxygen vacancies (Ov) and adsorbed oxygen species from the highly disordered structure could promote the redox property and oxygen release capability. In situ Raman and DRIFTS spectroscopy were used to identify a dynamic surface phase transformation during CO adsorption and oxidation. In combination with kinetic studies of CO oxidation, we conclude that there are two mixed mechanisms for CO oxidation over HDMO: the Langmuir-Hinshelwood (L-H) mechanism and the Mars-van Krevelen (MvK) mechanism.
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