A rigorous electrochemical synthesis protocol of ammonia with quantitative measurements of isotopes

The electrochemical synthesis of ammonia from nitrogen under mild conditions and using renewable electricity is in principle an attractive alternative.^1-4 Haber – Bosch, a demanding and energy-intensive process, which dominates the industrial production of ammonia. However, the electrochemical alternative faces considerable scientific and technical challenges^5.6 and most of the experimental studies reported to date only result in low selectivities and conversions. In fact, the amount of ammonia produced is usually so low that it is difficult to get it. 39 firmly assign to the electrochemical fixation of nitrogen.^7-9 and exclude contamination due to ammonia present in the air, human breath or conductive membranes of ions.⁹or generated from nitrogen-containing labile compounds (eg, nitrates, amines, nitrites, and nitrogen oxides) that are typically present in the gaseous nitrogen stream^ten, in the atmosphere or even the catalyst itself. Although these many and varied sources of potential experimental artefacts are beginning to be recognized and treated^11,12, concerted efforts to develop efficient electrochemical nitrogen reduction processes would benefit from comparative assessment protocols for the response and a standardized set of control experiments to identify, then eliminate or quantify sources of contamination. We propose here a procedure so rigorous that by making an essential use of ¹⁵NOT₂, allows us to reliably detect and quantify N electroreduction₂ at NH₃. We experimentally demonstrate the importance of various sources of contamination and show how to remove nitrogen-containing labile compounds present in nitrogen.₂ gas and how to perform quantitative isotope measurements with the cycling of ¹⁵NOT₂ gas to reduce both the contamination and the cost of isotope measurements. By following this protocol, we obtain negative results using the most promising pure metal catalysts in aqueous medium and confirm and successfully quantify ammonia synthesis by lithium electroplating in tetrahydrofuran.¹³.