Electrochemically Induced Generation of Extraneous Nitrite and Ammonia in Organic Electrolyte Solutions During Nitrogen Reduction Experiments

Oxidised nitrogen species (NO_x) are recognised as a major source of false-positive nitrogen reduction reaction (NRR) results. Even when addressed, NO_x are commonly eradicated at the initial stages of the experiment only. The present work demonstrates the shortcomings of this approach through a scrutiny of the evolution of NH₃, NO₂⁻ and NO₃⁻ during the reduction of N₂-saturated acetonitrile solutions with an Fe-modified electrode. Notwithstanding, thorough purification of the experimental setup, persistent evolution of NO₂⁻ during electroreduction was detected in solution and attributed to the pH increase at the electrode surface inducing the release of strongly adsorbed adventitious nitrite. This species could be then reduced to NH₃, while the rate of the NRR was unmeasurably low, as confirmed by ¹⁵N₂ reduction experiments. This effect of the electrochemically induced changes in pH has not been previously discussed in nonaqueous NRR, which is arguably the only effective means for the N₂ electroreduction to NH₃. This work also demonstrates that CH₃CN might present a suitable solvent for the NRR if a genuinely active catalyst that operates at reasonable overpotentials becomes available.