[Back]

A. Nagl, K. Hradil, J. Terzan, M. Zabilskiy, A. Pintar, S. Mostrou-Moser, J. Bokhoven van, K. Föttinger:
"Operando Studies on Supported Bimetallic Gold Catalysts";
Talk: OperandoVI - 6th International Congress on Operando Spectroscopy, Estepona, Malaga; 2018-04-15 - 2018-04-19; in: "Operando VI 6th International Congress on Operando Spectroscopy", (2018), 44.

Bimetallic catalysts have gained much interest as they offer a wide range of possibilities to tune catalytic properties by the choice of the second metal component. We study bimetallic Au catalysts supported on rutile powder with Ag and Ru as the promoter, both of which are known for their high affinity towards O2[1-3]. Especially of interest are the synergistic effects imposed by the second metal component for the selective oxidation of ethanol to acetaldehyde/acetic acid in gas phase.
In this contribution, we focus on in-situ and operando studies performed under both pre-treatment (heating under oxidative and reductive atmosphere) and reaction conditions. The evolution of the plasmon bands of the bimetallic nanoparticles was investigated using operando DR-UV-Vis spectroscopy and correlated with preliminary XAS measurements as well as information obtained by ex-situ material characterization (HR-TEM, STEM-EDX/HAADF, XPS and XRD): We observe alloy formation and find evidence for the oxidation of Ag and Ru. For AuRu, we show deactivation effects due to Ru(IV) formation. In addition, operando total scattering experiments were performed: Formation of the active nanoparticles as well as the dynamics of oxygen vacancies of TiO2 can be observed in the Pair Distribution Function (PDF).
Reactive species on the catalyst surface were monitored using operando DRIFTS, thus giving insight into the reaction mechanism: The Concentration Modulation Approach (CMA) involving periodic variation of the feed was employed with phase-sensitive detection (PSD), identifying relevant active species.


Acknowledgements
This project was financially supported by the Austrian Science Fund (FWF) by project [I2158-N28]. We acknowledge Diamond Light Source for time on Beamline/Lab I11 and I15 under Proposal [EE13826] and [EE13827]. We thank Dr. Sauer for the XPS measurements and Dr. Bernardi for the support with the TEM.

bimetallic catalysts, UV-Vis, DRIFTS, Pair Distribution Function Analysis