ametrine - 26-4-2024 at 08:44
It has been known for quite some time that electrolysis of nitrates (usually saltpeter) can produce NH3 by reduction of
NO3- at the cathode. However, undesirable reactions at the anode reduce the usefulness of this approach. Fortunately, there is a
solution: bipolar membranes.
A bipolar membrane (BPM) consists of a cation-exchange layer and an anion-exchange layer, separated by an interfacial layer. The idea is that the BPM
facilitates the disproportionation of water into H+ and OH- ions, which leave the BPM on opposite sides. This allows a current
to flow through the BPM while blocking ion transport across it.
Figure 1 from this article (open access) illustrates the approach:
Xu, Z., Wan, L., Liao, Y. et al. Continuous ammonia electrosynthesis using physically interlocked bipolar membrane at
1000 mA cm−2. Nat Commun 14, 1619 (2023). https://doi.org/10.1038/s41467-023-37273-7.
Unfortunately, the article shows that commercially available BPMs are not suitable for NH3 electrosynthesis, unlike the authors' proposed
design. This makes the approach less accessible to amateurs, and personally I don't have the knowledge or safety equipment to use reagents such as
trifluoroacetic acid (which is required to make the authors' BPM). Nonetheless, I thought that this was interesting enough to share anyway.
P.S. You can also use BPMs for splitting NaCl into NaOH and HCl (rather than NaOH and Cl2), and for other purposes.
mysteriusbhoice - 30-4-2024 at 01:06
I think electrochem synth of nitrates was extensively looked at before and sadly there have yet been any viable methods for it but this article does
nicely talk about NH3 from nitrates which is great for wastewater treatment maybe.
A recent buddy of mine made a meme tier nitrate generator that was actually competent and its called the sump aquarium where he put random compost in
an aquarium filled to the brim then got aeriators and several canister or sump filter setups and basically filtration and aeriation and eventually Ca
and Na nitrates end up in the sump filter which is leached. He succesfully made 1 rocket from it after a month of sumping.