In situ Low‐Energy Electron Microscopy of Chemical Waves on a Composite V‐oxide/Rh(110) Surface

Abstract

Chemical wave patterns and V‐oxide redistribution in catalytic methanol oxidation on a VOx/Rh(110) surface have been investigated in the 10‐4 mbar range with low‐energy electron microscopy (LEEM) and micro spot low‐energy electron diffraction (micro‐LEED) as in situ methods. V coverages of θV = 0.2 and 0.4 MLE (monolayer equivalents) were studied. Pulses display a c(2⨯2) pattern in the reduced part and (1⨯2) and c(2⨯8) structures in the oxidized part of the surface. At θV = 0.4 MLE (1⨯2) / (1⨯4) patterns with streaks along the [001] direction at the 1/8 positions are present on the oxidized part of the surface. This phase can be assigned to V‐oxide. Annealing the surface to 990 K under reaction conditions results in a macroscopic hole pattern in which holes of low VOx coverage are surrounded by a V‐oxide layer. Chemical waves propagate inside the holes as well as on the VOx covered parts of the surface.