Dynamics of Ultrathin V-Oxide Layers on Rh(111) and Rh(110) during Catalytic Reactions

by Prof. R. Imbihl (Institut für Physikalische Chemie und Elektrochemie, Leibniz-Universität Hannover)

Wednesday 22 Feb 2017, 10:00 → 11:00 UTC

Marie Curie Meeting room (ALBA Synchrotron)

We use photoemission electron microscopy (PEEM) and spectroscopic LEEM to study the dynamics of ultrathin V-oxide layers supported on Rh(111) and Rh(110) surfaces during catalytic methanol oxidation in the 10-4 mbar range. The spatially uniform VOx film obtained after preparation on Rh(111) condenses under reaction conditions upon heating in a macroscopic stripe pattern which at elevated temperatures (900 – 1000 K) transform into a spot pattern of circular VOx islands of 100 – 200 µm diameter. Within a critical distance of about 100 µm the islands move towards each other and coalesce. The coalescence process can be explained by a chemical polymerization/depolymerization equilibrium in which oxygen is required to detach small V6O12 clusters from a macroscopic VOx island. On Rh(110)/VOx catalytic methanol oxidation exhibits a quite different and much more complex behavior. We observe traveling interface modulations, dendritic growth of a VOx layer and unusual chemical wave patterns including wave fragments traveling along certain crystallographic directions.

References

[1] M. Hesse et al, Phys. Rev. Lett. 115 (2015) 136102.

[2] B. von Boehn, A. Preiss, R. Imbihl, PCCP 18 (2016) 19713.