We will present a very general and physically transparent framework, grounded in DFT calculations, to analyze adsorbate-adsorbate interactions on surfaces. This framework allows us to distinguish between electrostatic and electronic mechanisms of adsorbate-adsorbate interactions on surface. A fairly simple procedure was developed to calculate independently the different contributions to the adsorbate-adsorbate interaction energies.

This model was utilized to examine the effect of Cs adsorbates on the O2 dissociation reaction on Ag(111). The studies revealed that the main mode by which Cs affects the dissociation of O2 on Ag(111) is a long-range electrostatic interaction between the Cs-induced electric field and the dipole moment of relevant reaction intermediates. This electrostatic interaction stabilizes the transition state involved in the dissociation of O2, therefore lowering the activation barrier. The mechanisms can be generalized to systems involving electronegative and electropositive adsorbates on metal surfaces.

Ab intio thermodynamic simulations were employed to study how a working state of an alkali promoter and of the promoted catalytic material changes as a function of external conditions, i.e., pressure and temperature of reactants. In this context we have examined possible formation of Cs-oxide complexes and Ag-oxides as a function of the chemical potential of gas-phase O2 (pressure and temperature). We have also examined the effect of these oxygen-rich structures on surface chemical reactions.