Dynamic structure of highly disordered manganese oxide catalysts for low-temperature CO oxidation

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 (T-50 = 83 degrees C) was performed over a HDMO in the presence of H2O and CO2 . The specific reaction rate of 4.56 mu mol(CO).g(cat)(1).s(-1) at 90 degrees C was approximately 25 times and 15 times higher than those of bixbyitetype alpha-Mn2O3 and cryptomelane-type alpha-MnO2, respectively. With X-ray photon electron spectroscopy (XPS), we reveal that more surface oxygen vacancies (O-v) 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. (C) 2021 Elsevier Inc. All rights reserved.

Automated summary

The dynamic structures of a highly disordered manganese oxide catalyst and intermediates were thoroughly studied, showing excellent CO oxidation activity at low temperatures. The study identified two mixed mechanisms for CO oxidation over HDMO, including the Langmuir-Hinshelwood mechanism and the Mars-van Krevelen mechanism.