Weak binding mode of CH4 on rutile crystallites from density functional theory calculations

Abstract

In the recent years, the surfaces of oxides and fluorides have received considerable attention due to their suitability for emerging technologies such as fuel cells. Among these substances, well-known rutile TiO2, and rutile-like SnO2, MgF2 and ZnF2 are of particular interest owing to their utilization in a wide range of applications such as heterogeneous catalysis. In order to probe these materials for their catalytic activity, physisorption of small organic molecules, such as methane, on their respective dominant surfaces is of potential value. However, the lack of adequate experimental results on the adsorption energetics and geometries of binding particles, has stimulated a large number of computational studies. In this work, the van der Waals-driven sorption of CH4 on (110) face of all of the abovementioned structures has been examined computationally. A manifold of dispersion-corrected DFT methods was applied to evaluate the binding and surface energies as well as surface-induced atomic displacements. Only the most energetically favored configuration of the adsorption, has been examined. The calculated values were compared to the pertinent literature data, either theoretical or experimental, when available. Whilst optB86b-vdW produces the most consistent atomic displacements, despite its confinements, revPBE-D3 results in the most accurate adsorption energies for CH4-TiO2(110). Calculated surface energies were in agreement with the prior studies if available.