Producing ammonia from sustainable energy sources is a new and interesting route for decentralized production. Ammonia is an essential chemical for mainly fertilizer production but also an essential compound for the chemical industry. Normally ammonia is produced by large scale production – several thousand tons/day - by the Fritz-Haber process at 150-200 bar and 400 °C. Nature can, however, produce ammonia at ambient conditions using ATP as the energy source. This is done by bacteria living in symbiosis with plants who in exchange of sugar synthesize ammonia by the nitrogenase enzyme. In this presentation, the progress of synthesizing ammonia in a decentralized manner using an electrochemical process shall be discussed and in particular highlight some of the challenges.

There is a substantial very recent body of literature claiming ammonia synthesis by electrochemical routes and some of these data and their validity shall be critically reviewed. Often the ammonia is detected by the indo-phenol method which is an extremely sensitive method allowing for detection down to the ppb level. It is therefore mandatory that the amount of ammonia reported is quantified both in terms of turn over frequencies, but also in measured concentrations since contamination on the ppm level easily occurs leading to erroneous conclusions. Therefore, the experiments must also be followed up by proving that the nitrogen is coming from N₂ and not by activation of some nitrogen compounds being present either in the catalysts or in the electrolyte. This is extremely important since the most difficult step in this process is the activation of the nitrogen molecule that is the second most stable molecule in nature. It shall be demonstrated that this can convincingly be done by using isotopically labelled ¹⁵N₂. The ammonia synthesized can then subsequently be quantified using mass-spectroscopy, NMR or IR spectroscopy to prove that the source was indeed molecular nitrogen and not some other erroneous source of activated nitrogen. The advantage of using NMR or mass-spectroscopy shall be discussed and some of the tricks for measuring small amounts of ammonia in the presence of water shall be demonstrated. Examples of ammonia synthesis or lack of same for a number of catalysts tested shall be demonstrated.