Theoretical study of pattern formation during the catalytic oxidation of CO on Pt{100} at low pressures

Abstract

Theoretical studies have thus far been unable to model pattern formation during the reaction in this system on physically feasible length and time scales. In this paper, we derive a computational reaction-diffusion model for this system in which most of the input parameters have been determined experimentally. We model the surface on a mesoscopic scale intermediate between the microscopic size of CO islands and the macroscopic length scale of pattern formation. In agreement with experimental investigations ͓M. Eiswirth et al., Z. Phys. Chem., Neue Folge 144, 59 ͑1985͔͒, the results from our model divide the CO and O 2 partial pressure parameter space into three regions defined by the level of CO coverage or the presence of sustained oscillations. We see CO fronts moving into oxygen-covered regions, with the 1 ϫ 1 to hex phase change occurring at the leading edge. There are also traveling waves consisting of successive oxygen and CO fronts that move into areas of relatively high CO coverage, and in this case, the phase change is more gradual and of lower amplitude. The propagation speed of these reaction waves is similar to those observed experimentally for CO and oxygen fronts ͓H. H. Rotermund et al., J. Chem. Phys. 91, 4942 ͑1989͒; H. H. Rotermund et al., Nature ͑London͒ 343, 355 ͑1990͒; J. Lauterbach and H. H. Rotermund, Surf. Sci. 311, 231 ͑1994͔͒. In the two-dimensional version of our model, the traveling waves take the form of target patterns emitted from surface inhomogeneities.

Segregation and Selective Oxidation of Ni Atoms in Pt3Ni(111) in a Low-Pressure Oxygen Environment

“…Platinum is a precious and expensive noble metal commonly used as a catalyst in numerous chemical reactions. − For example, Pt is the most efficient catalyst in hydrogen-fuel cells and in CO oxidation. − Hence, lowering the amounts of Pt at the catalytic surface is a critical mission for technology transfer. Indeed, generally it has been reported that bimetallic alloys have superior catalytic properties with respect to the pure metal. − As an example, Stamenkovic and co-workers have reported that the Pt 3 Ni(111) surface is more active than Pt(111) and current state-of-the-art Pt/C catalysts for the oxygen reduction reaction in fuel cells .…”

Lifting of Ir{100} reconstruction by CO adsorption: An ab initio study

“…There can also be the formation of spatial patterns on the catalyst surface 31 , and these have been modelled recently within a sophisticated reaction-diffusion scheme32 . Although we are not aware of any literature concerning oscillatory reactions on Ir{100}, the experimental findings by Ali et al suggest that such oscillatory behavior may be present at temperatures above 900 K.…”

Spatiotemporal patterns in the Bär model induced by concentration-dependent diffusivities

“…Intermolecular forces, substratemediated interactions, and even blocking of adjacent sites by adsorbates are all factors that may cause the surface diffusion coefficients to vary with coverage [5,6]. Other nontrivial coupling modes have also been invoked [7,8].…”