Dipole corrections are applied to reduce the asymmetry imparted by adsorption at one side of the slab. Gaussian smearing of 0.2 eV is applied, and the energies were extrapolated to zero electronic temperature. The implicit solvation model is applied by using VASPsol with a dielectric constant of 78.4 for water solvent. The explicit model (details given in the solvent model section) has also been used to mimic the solvent-intermediate interactions. Brillouin zone sampling of the slab model is achieved using 3x3 x1 k-point and a Gamma point is used for molecules in a cubic box of dimension 12 Å. The k-point mesh, plane wave energy cutoff and number of atomic layers are verified for convergence. Spin-polarized calculations are carried out for studies involving molecular oxygen. The activation barriers are calculated using Climbing-Image Nudged elastic band method (CI-NEB). 55