The electrolyte, in which our NITRR

The electrolyte, in which our NITRR worked best, is a mixture of 1 M KOH and 1 M KNO3 (Figures S10-12). This electrolyte is beneficial for NO3- transfer, adsorption, and activation. In addition, the highly alkaline media can also suppress HER.56 Under such optimal conditions, our Ru-based electrocatalysts performed NITRR with H2 and ammonia as the only two products. Other side products including NO2-, NO, N2O, and N2 were undetectable (Figure S13). The experimental observations that non-electrocatalysis in KOH/KNO3 and electrocatalysis in KOH both yielded no ammonia and that 15NH4+ was tracked when 15NO3- was employed confirm that the detected ammonia is derived from the nitrate feedstock (Figures S14 and S15). The tensile strain inhibits HER, which is the only side-reaction of NITRR over Ru-ST-0.6, Ru-ST-5, and Ru-ST-12. This inhibition was more pronounced with catalysts having higher strain (Figure 2a). As a result, the scope of the potentials, in which >96% FENH3 was accessible, for Ru-ST-12 (0.2 to -0.3 V versus reversible hydrogen electrode (RHE)) was broader than those of Ru-ST-5 (0.2 to -0.2 V versus RHE) and Ru-ST-0.6 (0.2 to -0.1 V versus RHE).