Kinetics of Multisite-Occupancy Adsorption on Heterogeneous Solid Surfaces: A Statistical Rate Theory Approach

The theoretical approach to kinetics of adsorption on heterogeneous surfaces, developed recently by using the statistical rate theory (Rudzinski, W.; Panczyk, T. J. Phys. Chem. B 2000, 104, 9149) is generalized here for the case of multisite-occupancy adsorption. Theoretical kinetic isotherms are developed for the systems with quasi-Gaussian distribution of adsorption energies and when all of the segments (mers) of the adsorbing molecule are identical. The two extreme cases of surface topography, that is, patchwise and random topography, are considered. The obtained theoretical equations are used to correlate successfully experimental data for kinetics of oxygen adsorption on polycrystalline tungsten. Six experimental isotherms, measured at different pressures, can be successfully fitted by appropriate choice of only three parameters. The analysis of the estimated best-fit parameters makes drawing certain conclusions possible, concerning the energetic topography of the polycrystalline tungsten surface.