Ab Initio Density Functional Theory Studies of Hydrogen Adsorption at the V2O5(010) Surface

The adsorption of hydrogen at the V2O5(010) surface is studied by ab initio density functional methods in FP-LAPW calculations for V2O5(010) + H single layer slabs as well as in ab initio studies on size converged V2O5(010) + H surface clusters using the deMon method. Both theoretical approaches arrive at the same qualitative results. They confirm that hydrogen can adsorb at any of the five different surface oxygen sites forming a stable surface OH group. Hydrogen binding is found to be strongest at the vanadyl O(a) and the twofold bridging O(c) sites with differences close to the accuracy limit of the calculations. The OH group being formed at the O(c) site can relax outwards by an appreciable amount which is combined with an energy gain suggesting increased reactivity of this site. Computed excitation energies for hydrogen vibrations perpendicular to the V2O5(010) surface yield values for the most strongly binding O(a) and O(c) sites which lie in the range of typical experimental data for OH vibrations.