The exceptional high activity of oxide supported Au nanoparticles (NPs) makes them attractive catalysts for a variety of oxidation and reduction reactions.[1] Among many other reactions, supported Au NPs were found to be very active and stable catalysts for the selective CO2 hydrogenation to methanol (MeOH).[2] Au/ZrO2 and Au/ZnO catalysts, for example, have comparable activities for MeOH formation from CO2 on commercial Cu/ZnO/Al2O3 catalysts.[3] In addition, the Au/ZnO catalyst is also much more selective towards methanol formation (53% and 73% at 5 bar and 50 bar, respectively) compared to all other Au and Cu based catalysts, which predominantly catalyze CO formation via the reverse water gas shift (RWGS) reaction.[2-4] The origin of the outstanding catalytic properties of Au/ZnO catalysts is, however, not yet clear. A first step towards a deeper understanding is the identification of the surface species formed under reaction conditions, and their role in the reaction mechanism. Here we will present and discuss results of time resolved, in-situ diffuse reflectance FTIRS (DRIFTS) measurements performed during the methanol synthesis from CO2/H2 (1:3) at pressures up to 50 bar. Based on these measurements we will unravel the nature of the surface species formed upon exposure to the reaction gas mixture. From the comparison of the temporal evolution of these adsorbed species and the reaction rates recorded under identical reaction conditions, the role of reaction active species can be identified and differentiated from the reaction irrelevant side products (surface spectators).

Methanol synthesis from CO2 and H2 on Au/ZnO: Mechanistic insights from the analysis of adsorbed species formed under reaction conditions

253rd National Meeting (2017)

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