Application of statistical rate theory of interfacial transport to study solid surface heterogeneity from controlled-rate thermal desorption

Controlled-rate thermodesorption (CRTD) spectra are obtained by adjusting t he heating rate in such a way that the rate of desorption can be constant. A quantitative analysis of the obtained spectra is presented, based on appl ication of the statistical rate theory of interfacial transport (SRTIT) to describe both adsorption and desorption kinetics. The SRTIT approach relate s the rates of adsorption and desorption to the chemical potentials of the adsorbate in the gaseous and in the adsorbed phases. This quantitative anal ysis of the CRTD spectra yields the condensation approximation for the actu al adsorption energy distribution. For the purpose of illustration, an anal ysis is made of water desorption from a synthetic apatite mineral under CRT D and classical TPD conditions. The influence of the adsorption and desorpt ion rates is also discussed.