Catalysis on microstructured surfaces
Abstract
Employing photoelectron emission microscopy (PEEM) as a spatially resolving method the catalytic reduction of NO with CO and H2 has been investigated on microstructured composite surfaces in the 10–6 and 10–5 mbar range. By deposition of Ti and Rh onto a Pt(100) surface, domains of varying size and geometry are created in which the Pt is either surrounded by an inert Ti/TiO2 layer or by a reactive Rh layer. For the NO + CO reaction the behaviour of pulses in circular and ring-shaped geometries is studied. It is shown that the pattern forming properties of the Pt(100) substrate are significantly altered by size restrictions. In the NO + H2 reaction, which was investigated on Pt(100)/Rh microstructures, a strong diffusional coupling between the two metallic substrates occurs. This strong coupling presumably originates from highly mobile adsorbed hydrogen. Pattern formation and front nucleation take place preferentially at the Pt/Rh interface thus suggesting that this region exhibits a particularly high catalytic activity.