Microkinetic modelling of heterogeneous catalysis revisited: Adsorption energies can triumph over activation barriers

Abstract

In mechanistic studies of heterogeneous catalysis, emphasis is usually placed on the reaction barriers of individual reaction steps despite a long-standing empirical understanding of the importance of adsorption interactions. We construct a few archetypal reaction mechanisms and show the contribution of the adsorption interactions to the overall reaction rate. We investigated the degree of rate control and the reaction rate as the function of the adsorption interactions. The results show that even when leaving the reaction barriers intact, changes in the adsorption interaction have profound effects on the overall turn-over frequencies. This was also shown on a real-life example of ethane dehydrogenation. We re-confirm that although finding the rate-determining step is important in catalyst optimisation, improving the adsorption is at least equally important.