In this work, we study the effect of Na + doping in the electronic structure and the OER of the more stable Li That the Na + doping promotes the generation of lithium vacancies can be first checked by comparing the V Li formation energy obtained with and without Na + for the [1 100] ST-3 surface. We explore different Li + substitutional sites for Na doping (see Figure and Table in the SI material). For the more energetically stable Na-doping site, we calculate the lithium vacancy energy formation for different remaining Li + sites (see Figure and Table in the SI file). In line with the experimental observation, the formation energy in the presence of Na + for the more favorable vacancy site is 150 meV smaller than for the pristine surface (see Table in the SI file).