Non-Arrhenius behavior in the initial rate of a catalytic-surface reaction: Theory and Monte Carlo simulation

We have identified the factors contributing to the compensation effect in the initial rate of a bimolecular surface reaction, the kinetics of which are influenced by adsorbate lateral interactions. A simple theory, based on the quasichemical approximation, can predict the temperature ranges over which compensation is the most pronounced in Monte Carlo simulations of the initial rate. Both the simulations and the theory reveal an interesting phenomenon - apparent negative activation energies, which occur when the activation energy for reaction increases with increasing temperature faster than k_BT. This phenomenon could contribute to experimentally observed decreases seen in the rate of the CO oxidation reaction on several single-crystal metal surfaces.