Dresden 2017 – scientific programme

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O: Fachverband Oberflächenphysik

O 93: Heterogeneous Catalysis: Experiment

O 93.6: Talk

Thursday, March 23, 2017, 16:45–17:00, TRE Phy

Electronic properties of Au nanoparticles on CeO₂ in the water-gas shift (WGS) reaction using operando X-ray absorption spectroscopy — •Joachim Bansmann, Gabriela Kucerova, Ali Abdel-Mageed, and R. Jürgen Behm — Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany

Small Au nanoparticles (NPs) on ceria surfaces are important catalysts in the CO oxidation and water-gas shift (WGS) reaction. The activity and deactivation during time on stream (TOS) of those catalysts strongly depends on the nature (oxidic and/or reductive) of pre-treatments. Here, we will concentrate on the oxidation state and the size of the Au nanoparticles after different pretreatments and during reaction using ex-situ characterization techniques (e.g. XPS) as well as operando methods such as XANES/EXAFS and diffuse IR spectroscopy (DRIFTS). Reductive pretreatments lead to metallic Au particles, whereas oxidic pretreatments results in partially oxidized Au NPs (depending on the temperature).

Employing operando X-ray absorption spectroscopy, we followed the changes in chemical state and size of the Au particle during the water-gas shift reaction at 180^∘C. The results are discussed in comparison with the activity and deactivation of these catalysts considering also effects such as blocking of active sites by formation of carbonates and formates. Finally, we compare our findings with results obtained in the CO oxidation [1] using similar Au/CeO₂ catalysts.

[1] A. Abd El-Moemen et al., J. Catal. 341 (2016) 160