Can liquid ammonia NH3 be electrolyzed?

  • #1
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Can liquid ammonia NH3 be electolyzed to produce H2 and N2?

I have heard of ammonia cracking using high temperature and a catalyst but I was wondering if electrolysis would be an easier way to produce hydrogen from ammonia. The H2 could be fed into a PEM fuel cell to produce electricity to run a car for example.
 

Answers and Replies

  • #3
Borek
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Isn't ammonia commercially made from hydrogen, which makes cracking it for hydrogen a bit absurd?
 
  • #4
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Um, you can truck an ISO tank of liquid ammonia without too much difficulty or danger, but cryo hydrogen has 'handling issues', and gaseous hydrogen at economically portable bulk must be transported in comparatively small diameter tanks to withstand the pressures.

Tangential, hydrogen gas is not as slippery as helium, but does have a nasty reputation for escaping through 'well sealed' joints. There's another factor. You know when you have an ammonia leak, it stinks. You know when you have a hydrogen leak when it explodes at very high velocity. Upside, is that a modest hydrogen leak will go upwards, so wary ventilation may suffice. Hindenburg's spectacular demise was more due to the highly-flammable coated outer skin than the inner ballonettes' content...

FWIW, liquid anhydrous ammonia makes an excellent solvent for light alkali metals such as sodium and potassium, producing totally beautiful, deep-blue solvation colours...

Back to OP's query, 'YES, BUT...'
https://www.sciencedirect.com/science/article/pii/S0360319916319346

Given I noticed this reference while checking I'd remembered the alkali stuff --That picturesque 'Scientific American' article was a long, lonnng time ago !!-- a search engine should be able to find much that is NOT pay-walled...
 
  • #5
hmmm27
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NH3 is great for storage and transportation (compared to H2) as it liquefies at relatively low pressures. You could, conceivably, have a small tank, of H2 for commuting with a puddle of ammonia kept at the bottom to assuage range anxiety ; top it up for long-range driving.
 
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  • #6
DrDu
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Um, you can truck an ISO tank of liquid ammonia without too much difficulty or danger,...
From the Saftety data sheet:
H221: Flammable gas H331: Toxic if inhaled H314: Causes severe skin burns and eye damage H400: Very toxic to aquatic life

Given the alternative, I'd rather prefer hydrogen.
Why not rather use urea, btw?
 
  • #7
TeethWhitener
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I imagine the OP's question was more about circumventing the issue with onboard hydrogen storage in vehicles. For which (as a few posters have pointed out) ammonia is not a bad solution--especially considering the alternatives right now generally involve alkali hydrides or borohydrides. Ammonia liquefies at ~7 atmospheres, it's pretty easy to handle, it's dirt cheap, and the electrolysis products (in the absence of oxygen) are environmentally benign.
Why not rather use urea, btw?
At least one group is working on it. Industrially, urea is made from ammonia, so it's adding an extra step. Also, electrolysis of urea releases CO2--though one could argue it's still carbon-neutral, as the CO2 is captured to make urea in the first place. Urea is certainly safer than ammonia, but again, ammonia is pretty straightforward to handle on an industrial scale. (Also, how concerned about safety are we, really, if we're willing to walk around all day with several grams of lithium-graphite directly adjacent to our crotches?:smile:)
 
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