Quantum-chemical calculations of thermodynamic characteristics of some heterogeneous catalytic processes with the use of multilayer cluster models

Abstract

The approaches to estimating the changes in enthalpy, entropy, and Gibbs energy of adsorption processes and heterogeneous catalytic reactions on the basis of the quantum chemical calculation data were studied. By comparing with the experimental data on CO adsorption on the anatase (TiO2) surface, the applicability of the developed multilayer cluster model for calculation of the adsorption energy (enthalpy) was shown. The data on the calculation methods of the entropy change in heterogeneous processes were analyzed. The use of the theories of an ideal two-dimensional gas and an ideal two-dimensional lattice gas for estimating a configuration contribution to the entropy of a heterogeneous process was studied. The density of adsorption centers on the (101) anatase surface and the population corresponding to the standard state of an ideal two-dimensional gas were calculated. The consistency of the studied models at low populations was shown, and the limits of their applicability were established.