Kinetics of adsorption on energetically heterogeneous surfaces

Abstract

Rate models for adsorption and desorption on a non-uniform surface are derived using the “Extent of Reaction Effect” which describes the behaviour of large systems of parallel reactions. When the rate models and the resulting isotherm are fitted to data taken from the literature, very good agreement is found between the fitted model and the data. The new isotherm also provides an explanation for cases where physisorption is observed to follow Langmuir's dissociative chemisorption isotherm. Extensions of our rate model are presented for the case where a precursor state exists. This approach leads to two well-established isotherms: the Freundlich isotherm and the “generalized Freundlich” isotherm proposed by Sips.