Modeling of surface explosion of NO+H2NO+H2 reaction on Pt(1 0 0): Mean-field analysis and dynamic Monte Carlo simulations

Surface explosions which occur, for example, in field ion microscopy experiments on catalytic reduction of nitric oxide by H2H2 over Pt surfaces are studied as a function of partial pressures and initial species covering. Using a Langmuir-Hinshelwood mechanism of reaction a simplified model with only four adsorbed species NO,H,O,N is constructed. This minimal model, in the mean field approximation (MF), shows a bistability, which is associated to the explosive phenomena. Near the transition point between these states there exist a peak in the production rates which is associated to an abrupt growing of the empty sites, far from the transition point the production rates only attains a stationary value. Dynamic Monte Carlo simulations were performed and compared with the MF results. Dynamic Monte Carlo simulations allow to study the spatial development of explosions. It is shown that at the peak of the production rates there is an island formation of adsorbed NO surrounded by empty sites which provokes the rapid decomposition of NO into adsorbed N and O and, consequently, a large production of N2N2 and H2OH2O.

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