Pattern Formation in Catalytic H 2 Oxidation on Rh: Zooming in by Correlative Microscopy.

Spatio-temporal nonuniformities in H 2 oxidation on individual Rh( h   k   l ) domains of a polycrystalline Rh foil were studied in the 10 -6 mbar pressure range by photoemission electron microscopy (PEEM), X-ray photoemission electron microscopy (XPEEM), and low-energy electron microscopy (LEEM). The latter two were used for in situ correlative microscopy to zoom in with significantly higher lateral resolution, allowing detection of an unusual island-mediated oxygen front propagation during kinetic transitions. The origin of the island-mediated front propagation was rationalized by model calculations based on a hybrid approach of microkinetic modeling and Monte Carlo simulations.