On the applicability of Arrhenius plot methods to determine surface energetic heterogeneity of adsorbents and catalysts surfaces from experimental TPD spectra

Recovering adsorption energy distribution from experimental data belongs to most difficult problems of adsorption science. Ln the case when thermodeso rption data are used as a source of information, that difficult problem is overcome by the common use of the Arrhenius plot methods. So, we decided to carry out an extensive model investigation to show, how reliable informati on concerning the surface energetic heterogeneity is obtained by using the Arrhenius plot methods. Like in our previous publications we have used the Statistical Rate Theory of Interfacial Transport to describe the adsorption /desorption kinetics. Our model investigations showed, that the Arrhenius p lot methods, cannot provide reliable information about the surface energeti c heterogeneity. Moreover, for strongly heterogeneous surfaces a linear rel ationship exists between the logarithm of the pre-exponential constant and the adsorption energy, for certain adsorption coverages. That kind of compe nsation effect has, so far, been ascribed to interactions between the adsor bed molecules. The failure of the popular Arrhenius plot method puts, as an urgent agenda, the development of reliable methods for recovering adsorpti on energy distribution from the thermodesorption data. (C) 2000 Elsevier Sc ience B.V. All rights reserved.