Methanol plasma-catalytic oxidation over CeO2 catalysts: Effect of ceria morphology and reaction mechanism

The effect of CeO2 morphology on efficient methanol oxidation and the detailed reaction mechanism were investigated in a plasma-catalytic system at room temperature. CeO2 with different morphologies (i.e. rod, particle, and cube) were prepared by a hydrothermal method and characterized by the X-ray diffraction (XRD), scanning electron microscopy (SEM), Brunauer-Emmett-Teller (BET), Raman and X-ray photoelectron spectroscopy (XPS). Among the three CeO2 morphologies, CeO2 rod catalyst had the most amount of oxygen vacancy. All the catalysts were tested for methanol oxidation in plasma, and the results showed that CeO2 rod catalyst exhibited the highest methanol conversion (94.1%), CO2 selectivity (90.1%) and ozone suppression. In situ Raman spectroscopy experiments proved that the performance of ozone decomposition was related to the amount of oxygen vacancy in CeO2. Surface oxygen vacancies in CeO2 rod catalyst acted as active sites for ozone decomposition, resulting in more reactive oxygen species that could effectively oxidize methanol and increase CO2 selectivity in the plasma-catalytic system. Finally, the evolution of adsorbed intermediate species and some key steps of methanol oxidation were discussed based on the results of plasma-catalytic in situ Fourier Transform Infrared Spectrometer (FTIR) experiments.