In Figure , we show the three cases studied and their calculated E dis (X). We obtain Considering as a fact that Na + or K + doping promotes V Li generation, we next focus on the Na + case to study the OER for the Na-doped [1 100] ST-3 surface in the presence of one V Li as initial state. In this Section, we will only show the results obtained with HSE α=0.48. The initial state of the simulated OER process for the Na-doped surface is depicted in the inset a) of Figure . It can be observed that there are a Na surface ion (in yellow), a hole polaron at the surface dimer O 2 (in purple) and the initial lithium vacancy is indicated with a cross. As mentioned before, we remark that both the Na substitutional site and the initial lithium vacancy are the ones that resulted more energetically stable.