Spontaneous N2 formation by a diruthenium complex enables electrocatalytic and aerobic oxidation of ammonia.

The electrochemical conversion of ammonia to dinitrogen in a direct ammonia fuel cell (DAFC) is a necessary technology for the realization of a nitrogen economy. Previous efforts to catalyse this reaction with molecular complexes required the addition of exogenous oxidizing reagents or application of potentials greater than the thermodynamic potential for the oxygen reduction reaction—the cathodic process of a DAFC. We report a stable metal–metal bonded diruthenium complex that spontaneously produces dinitrogen from ammonia under ambient conditions. The resulting reduced diruthenium material can be reoxidized with oxygen for subsequent reactions with ammonia, demonstrating its ability to spontaneously promote both half-reactions necessary for a DAFC. The diruthenium complex also acts as a redox mediator for the electrocatalytic oxidation of ammonia to dinitrogen at potentials as low as −255 mV versus Fc0/+ and operates below the oxygen reduction reaction potential in alkaline conditions, thus achieving a thermodynamic viability relevant for the future development of DAFCs. The use of ammonia as an alternative fuel relies on its electrochemical conversion to dinitrogen in a fuel cell. Now a stable metal–metal bonded diruthenium complex is shown to spontaneously produce dinitrogen from ammonia under ambient conditions and is also able to electrocatalyse the oxidation of ammonia to dinitrogen at low potentials.