Dynamic Monte Carlo simulation of the [formula omitted] reaction on Pt(100): TPR spectra

Abstract

The catalytic reduction of nitric oxide by hydrogen over a Pt surface is studied using a dynamic Monte Carlo (MC) method on a square lattice under low pressure conditions. Using a Langmuir–Hinshelwood reaction mechanism, a simplified model with only four adsorbed species (NO, H, O, and N) is constructed. The effect on the NO dissociation rate, the limiting step in the whole reaction, is inhibited by co-adsorbed NO and H2 molecules and is enhanced both by the presence of empty sites and adsorbed N atoms at nearest neighbors. In these simulations, several experimental parameter values are included, such as: adsorption, desorption and diffusion of the reactants. The phenomenon is studied while varying the temperature over the 300–550 K range. The model reproduces well-observed TPD and TPR experimental results. For the whole NO+H2 reaction, the phenomena of “surface explosion” is observed and can be explained as the result of the abrupt production of N2 due to both the autocatalytic NO decomposition favored by the presence of vacant sites and the development of inhomogeneous fluctuations. MA simulations also allow a visualization of the spatial development of the surface explosion as heating proceeds.