Figure : TheoreUcal criteria for a successful mediator of electrochemical NH3 synthesis, adapted with permission from Ref. . Criteria include stability of a N vacancy at the SEI and the ability to dissociate N2 at a reasonable rate under ambient condiUons. The temperature to achieve N2 dissociaUon turnover frequency of 1 s-1 was calculated by assuming a transiUon metal BEP scaling from Ref. . Here, we idenUfy both Ca and Mg as feasible mediators for the process, in addiUon to Li.