Methods culated using the revised Perdew-Burke-Ernzerhof functional (RPBE) to better account for chemisorption. The electron-core interactions were described via a projector augmented wave (PAW) method. A Γ centered 5 x 5 x 1 k-point grid was used to calculate the adsorption energies. The electronic self-consistent-field (SCF) was converged up to 10 -6 eV using the Gaussian smearing scheme with a width of 0.05 eV, with the ionic geometry being converged to energetic differences below 10 -5 eV. The DFT-D3 Van-der-Waals (vdW) correction of Grimme was applied to include dispersion effects during molecular adsorption.