Influence of dipole interactions on surface reactions

Abstract

Electrostatic interactions between dipoles of adsorbed molecules can influence reaction mechanism and kinetics. Repulsive interactions can increase the rate of surface reactions, whereas attractive interactions can decrease the rate of reaction because of an increased stability of the adsorbed species. With formic acid decomposition on Ni surfaces attractive dipole interactions resulted in the formation of a condensed surface phase, which decomposed with autocatalytic kinetics. The formation of the condensed phase was affected by both crystallographic structure as well as adsorption temperature by affecting the approach to an equilibrium configuration.

Attractive dipole interactions also affect the orientation of molecules on a surface, thus facilitating reactions that might not otherwise occur. The formation of methyl formate from formaldehyde on a W(100)–(5 × 1)C surface has been attributed to the favourable alignment of formaldehyde molecules stemming from attractive dipole interactions.