(Invited) Electrosynthesis of Ammonia from Dinitrogen in Non-Aqueous Media
Authors: Cherepanov Pavel , Krebsz Melinda , Hodgetts Rebecca , Du Hoang-Long , Suryanto Bryan H R , Azofra Luis M. , MacFarlane Douglas R. , Simonov Alexandr N. 
Published: May 2020

Since early 2018, the nitrogen reduction reaction to ammonia (NRR) has become a focus of active research as an approach to sustainable production of ammonia to support and eventually replace the century-old yet highly robust Haber-Bosch catalytic technology. More than one hundred reports on the successful NRR in aqueous electrolyte solutions catalysed by a comparatively wide range of materials have been published by the end of 2019, though the reported ammonia yield rates (<100 pmol s-1 cm-2, per geometric surface area of the electrode) and faradaic efficiencies (< 20%) are typically low. In fact, the observed amounts of NH3 produced in aqueous media are most often comparable to the level of adventitious nitrogen-based contaminants, thereby questioning the genuine nature of the reported NRR.

The problems of the aqueous NRR, in the first place low faradaic efficiency, can be effectively addressed by employing aprotic electrolyte media for the electrochemical reduction of dinitrogen.1-2 Under such conditions, the prevalence of the NRR over the competing and undesirable in this context hydrogen evolution reaction is suppressed due to the significantly higher solubility of N2 than in water and controlled supply of the proton source. Ammonia electrosynthesis in organic media can be realised in at least two ways — either via direct electrocatalytic reaction,3-4 or through a lithium-mediated process.5-6 Both approaches have their pros and cons, and both are currently investigated in our groups. The talk will focus on some of the experimental challenges and pitfalls relevant to the non-aqueous NRR and on our recent progress in this area.

References

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