Arrangement of acid sites on the surfaces of anatase titanium dioxide nanoparticles according to cluster models

Computer-implemented cluster models have been devised for ∼2-nm anatase nanoparticles with exposed (001) and (100) faces. The Lewis acid sites occurring in these faces have been characterized by calculating the enthalpy of CO adsorption. In the Ti₁₁₄O₂₂₈ and Ti₁₈₇O ₃₇₆H₄ clusters, the corner oxygen atoms compensating the electric charge are bound to titanium atoms by double bonds with a length of approximately 1.7 Å, which is in agreement with experimental data. The average enthalpy of CO adsorption on the (001) and (100) faces at a zero coverage is -87.62 and -135.31 kJ/mol, respectively. The deviation from the average value is 20.2 and 8.8%, respectively. The average enthalpy of CO adsorption for the Ti₁₁₄O₂₂₈ cluster is -129.40 kJ/mol, and that for the Ti₁₈₇O₃₇₆H₄ cluster is -119.79 kJ/mol.