Theory of thermodesorption from energetically heterogeneous surfaces: Combined effects of surface heterogeneity, readsorption, and interactions between the adsorbed molecules
W. Rudzinski et al., Theory of thermodesorption from energetically heterogeneous surfaces: Combined effects of surface heterogeneity, readsorption, and interactions between the adsorbed molecules, LANGMUIR, 16(21), 2000, pp. 8037-8049
Theoretical analysis of thermodesorption from energetically heterogeneous s
olid surfaces is commonly based on the absolute rate theory in the form of
the Wigner-Polanyi (W-P) equation, which neglects readsorption. As a conseq
uence, the results of such analyses contain errors of unknown type and magn
itude. Here we show that the application of the statistical rate theory of
interfacial transport, instead of the W-P equations, leads to adsorption/de
sorption rate equations which simplify taking readsorption effects into acc
ount. An extensive model investigation is presented to show how neglecting
readsorption can affect the theoretical analysis of experimental TPD peaks.
Our investigation shows that readsorption can mimic effects which are actu
ally due to surface energetic heterogeneity and/or to interactions between
the adsorbed molecules. In addition to illustrative model calculations, the
role of readsorption is also demonstrated by a quantitative analysis of sp
ectra of hydrogen thermodesorption from a nickel catalyst.