Density functional theory study of rutile VO2 surfaces

TL;DR

This study uses density functional theory to analyze rutile VO2 surfaces, revealing the most stable surface orientation, particle morphology, and oxidation behavior, with implications for redox properties and surface chemistry.

Contribution

It provides new insights into the surface energies, morphology, and oxidation states of rutile VO2 surfaces using DFT calculations.

Findings

(110) is the most stable surface orientation.

VO2(110) surface is oxidized under various conditions.

Surface vanadyl species are more favorable than peroxo species.

Abstract

We present the results of a density functional theory (DFT) investigation of the surfaces of rutile-like vanadium dioxide, VO2(R). We calculate the surface energies of low Miller index planes, and find that the most stable surface orientation is the (110). The equilibrium morphology of a VO2(R) particle has an acicular shape, laterally confined by (110) planes and topped by (011) planes. The redox properties of the (110) surface are investigated by calculating the relative surface free energies of the non-stoichiometric compositions as a function of oxygen chemical potential. It is found that the VO2(110) surface is oxidized with respect to the stoichiometric composition, not only at ambient conditions but also at the more reducing conditions under which bulk VO2 is stable in comparison with bulk V2O5. The adsorbed oxygen forms surface vanadyl species much more favorably than surface peroxo species.