Electrochemically Induced Generation of Extraneous Nitrite and Ammonia in Organic Electrolyte Solutions During Nitrogen Reduction Experiments. Issue 9 (30th March 2021)

• Record Type: Journal Article
• Authors: Hodgetts, Rebecca Y.; Du, Hoang‐Long; MacFarlane, Douglas R.; Simonov, Alexandr N.
• Is Part Of: ChemElectroChem. Volume 8:Issue 9(2021)
• Page Start: 1596
• Page End: 1604
• Publication Date: 2021-03-30
• Subjects: nitrogen reduction reaction -- acetonitrile -- pH effect -- electrocatalytic reduction; Electrochemistry -- Periodicals; 541.37
• DOI: 10.1002/celc.202100251
• Languages: English
• ISSNs: 2196-0216

Abstract

Abstract: 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 15 N2 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 CH3 CN might present a suitable solvent for the NRR if a genuinely active catalyst that operates at reasonable overpotentials becomes available. Abstract : Margin of error : Organic electrolyte media present a host of challenges for the N2 reduction reaction (NRR), which are presented herein for the [ n Bu4 N][PF6 ]+CH3 CN system. In particular, the electrochemically induced release of NO x species is identified as a potential source of the false‐positive NRR. At the same time, the examined electrolyte‐solvent combination is sufficiently stable under electroreductive conditions and is therefore suitable for the reliable NRR studies.