Revealing the significant differences of CO plasma oxidation on β-MnO2 catalyst in in- and post-plasma catalysis configurations using operando DRIFTS-MS

Abstract

The position of the catalyst in a plasma reactor has an important effect on performance of plasma driven catalytic reaction. An operando diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and mass spectrometry (MS) has been used to investigate CO oxidation on MnO2 catalyst in in-plasma catalysis (IPC) and post-plasma catalysis (PPC) configurations. It was found that the catalyst in IPC configuration has higher CO conversion and CO2 selectivity than that in PPC configuration. Operando DRIFTS-MS analysis showed that the IPC configuration generated more reactive oxygen species (MO) on the catalyst surface than the PPC configuration, where MO, M2+-O22–, and M+O2– are important reactive species promoting CO oxidation to monodentate carbonate that is easy to gasify to gaseous CO2. The physical adsorbed O3 on the catalyst in PPC configuration converts to M2+-O22– which combines with CO to form bidentate carbonates that is difficult to gasify to gaseous CO2. The mechanisms of CO oxidation on the catalyst in IPC and PPC configurations are discussed.