Recent progress in determination of energetic heterogeneity of solids from adsorption data

This review gives a brief outline of the theory of gas adsorption on heterogeneous solid surfaces in order to present recent progress in determination of adsorbent heterogeneity from adsorption data. First, the concept of adsorbent heterogeneity is presented with special emphasis on the introduction of the distribution function of adsorption energy, which is generally accepted as a quantitative characteristic of adsorbent heterogeneity. This function is usually obtained by inverting the fundamental integral equation, which represents the overall adsorption isotherm. Analytical and numerical methods for solving this integral equation with respect to the energy distribution function are reviewed from the viewpoint of their utility for characterizing the energetic heterogeneity of solid surfaces. Special consideration is given to numerical methods for evaluating energy distribution from adsorption data because they do not require an additional assumption about the shape of this distribution. The theoretical and numerical aspects of determination of the energy distribution from adsorption data are also discussed in order to recommend the best methods for its evaluation. To illustrate the utility of these methods for determining adsorbent heterogeneity, the energy distributions are calculated from adsorption data available in the literature.