Chapter 12 - Multisite Occupancy Adsorption on Heterogeneous Solid Surfaces

Abstract

This chapter describes heterogeneous solid surfaces in terms of multisite occupancy adsorption. Studies were done considering the problem of evaluating the dispersion of ɛ n values, as the dispersion of e ˆ was known. The result depends on whether the heterogeneous solid surface is characterized by a random or a patchwise surface topography. With an increasing number of alkyl segments (mers) in the adsorbate molecule, the adsorption energy distribution becomes steadily flatter. In a study described in the chapter, it was found that the numerical method of evaluating θ t can be applied only with a discrete distribution of adsorption energies. This proposal does not possess a compact analytical form and is only suitable for further thermodynamic analysis. In another study described in the chapter, the surface activity coefficients for a given patch i were assumed to be functions of the local concentration on this patch, θ I , in terms of patchwise topography. In the case of multisite occupancy adsorption of molecules composed of identical segments, the surface topography manifests itself by the additional entropic term θ t (n-1) by which pressure is multiplied in the case of random surface topography.