CO2 Reduction to Methanol on Au/CeO2 Catalysts: Mechanistic Insights from De-Activation and SSITKA Measurements

Aiming at a mechanistic understanding of the methanol (MeOH) synthesis from CO2/H2 over Au/CeO2 catalysts and the activation/deactivation of these catalysts, we have investigated these processes by a combination of kinetic measurements, time resolved in situ diffuse reflectance FTIR spectroscopy (DRIFTS) measurements and structural characterization by X-ray diffraction (XRD) and scanning transmission electron microscopy (STEM). Kinetic measurements indicated a rapid activation phase, followed by a continuous slow deactivation. The deactivation rate of CO formation (reverse water gas shift reaction) is higher than that of methanol formation, the selectivity towards MeOH increases with time on stream. The activation of the catalyst is attributed to a rapid initial reduction of the support (formation of O-vacancies). STEM imaging and XRD measurements revealed that sintering of Au nanoparticles is negligible, the later deactivation is attributed to the slow build-up of site blocking adsorbates, specifically s...