Taking into Account Energetic Topography in Adsorption on Heterogeneous Surfaces

F. BULNES; M. NAZZARRO; J. L. RICCARDO; G. ZGRABLICH; RAMIREZ PASTOR A. J,

ADSORPTION SCIENCE & TECHNOLOGY

MULTI SCIENCE PUBL CO LTD

Año: 2007 vol. 25 p. 365 - 384

0263-6174

Adsorption of gases on heterogeneous surfaces is reviewed highlighting models that are able to take into account energetic topography effects. The basic ideas are contained in the fundamental Generalized Gaussian Model, developed to represent mobile adsorption on heterogeneous surfaces at low coverage, where the energetic topography is considered through an adsorptive energy distribution with a spatial correlation function. Adsorbate molecules interact among them via Lennard-Jones interactions. Model predictions are compared to Monte Carlo simulations of adsorption on heterogeneous solids obtained by doping a pure crystalline solid with different concentrations of impurities. Energetic topography effects are shown to be important and they are correctly predicted by the model at low coverage. In addition, a simplified patchwise model is also considered. Adsorption of particles with nearest-neighbor attractive and repulsive interactions is studied through Monte Carlo simulation on bivariate surfaces characterized by patches of weak and strong adsorbing sites of size l. Patches are considered to have either a square or a strip geometry and they can be either arranged in a deterministic ordered structure or in a random way. Quantities are identified which scale obeying power laws as a function of the scale length l. Consequences of this finding are discussed for the determination of the energetic topography of the surface from adsorption measurements.