Hole patterns in ultrathin vanadium oxide layers on a Rh(111) surface during catalytic oxidation reactions with NO

Various oxidation reactions with NO as oxidant have been investigated on a partially VO_x covered Rh(111) surface (θ_V = 0.3 MLE) in the 10^-4 mbar range, using photoelectron emission microscopy (PEEM) as spatially resolving method. The PEEM studies are complemented by rate measurements and by low-energy electron diffraction. In catalytic methanol oxidation with NO and in the NH₃ + NO reaction, we observe that starting from a homogeneous surface with increasing temperature first a stripe pattern develops, followed by a pattern in which macroscopic holes of nearly bare metal surface are surrounded by a VO_x film. These hole patterns represent just the inverse of the VO_x distribution patterns seen if O₂ instead of NO is used as oxidant.