## Northwestern team develops solid acid electrochemical cell for the production of hydrogen from ammonia

##### 03 November 2020

Researchers at Northwestern University, with colleagues from SAFCell, Inc, have demonstrated the production of high-purity hydrogen by thermal-electrochemical decomposition of ammonia at an intermediate temperature of 250 ˚C. A paper on their work is published in the journal Joule.

The process is enabled by use of a solid-acid-based electrochemical cell (SAEC) in combination with a bilayered anode, comprising a thermal-cracking catalyst layer and a hydrogen electrooxidation catalyst layer.

Cs-promoted Ru on carbon nanotubes (Ru/CNT) serves as the thermal decomposition catalyst, and Pt on carbon black mixed with CsH2PO4 is used to catalyze hydrogen electro-oxidation.

Cells were operated at 250 ˚C with humidified dilute ammonia supplied to the anode and humidified hydrogen supplied to the counter electrode.

A current density of 435 mA/cm2 was achieved at a potential of 0.4 V and ammonia flow rate of 30 sccm. With a demonstrated Faradic efficiency for hydrogen production of 100%, the process yields hydrogen at a rate of 1.48 molH2/gcath.

Resources

• Lim et al. (2020) “Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia,” Joule doi: 10.1016/j.joule.2020.10.006

So where does the feedstock NH₄ come from?
Modern ammonia production seems to rely on H₂ that's already been produced.
PS - nothing on the SAFCell site, and the DOI doesn't lead anywhere (posted too soon, perhaps).

@Bob

There are truly enormous projects underway for the production of hydrogen from renewables, and then its transport as ammonia, at Pilbarra in Australia and Saudi Arabia amongst others.

This is the other half of the circle.

NH3 has three times higher volumetric energy density than liquid hydrogen (-253°C) and thus more easily transported.

Global transport of liquid ammonia is about 10 Mt/yr.

No liquid hydrogen transport ships currently exist, to my knowledge (there is probably some obscure vessel out there...).

@Thomas Pedersen

Japan has a liquid hydrogen transporter ship on trial:
https://www.ft.com/content/8ae16d5e-1bd4-11ea-97df-cc63de1d73f4

I don't see the point myself, and prefer ammonia or others.

re: This is the other half of the circle.
Thanks, Davemart

Having authored NH₃ safety content for an agricultural tank manual, I'm [only] a bit surprised that it is considered for H₂ energy transport. Of course, any form of concentrated stored energy has risks.

Minot, or Hindenburg? When driving, and I find myself following an anhydrous tank out here in rural country, I keep my distance and pay attention to the wind direction.

@Bob Niland:

Here is an in depth article on the production and transport costs of various fuels, liquid hydrogen, LNG, ammonia, DME and methanol:
https://www.sciencedirect.com/science/article/pii/S2352484720312312

'Estimating boil-off cost for LNG, liquid ammonia, methanol, DME, and liquid hydrogen.

LNG tanker capital cost is 15% and 40% higher than ammonia and methanol tankers.

Transporting cost of liquid ammonia and liquid hydrogen are 1.09 $/GJ and 3.24$/GJ.

Methanol and DME has 10% and 25% lower transportation cost than LNG.

Social cost of carbon is calculated for various energy carriers.'

Its clear enough why ammonia should be preferred to LNG let alone liquid hydrogen in the big projects in Australia and Saudi, although the Japanese are also developing liquid hydrogen carrier ships, which I don't understand.

I also don't get why they are looking at ammonia rather than methanol or DME, which as far as I can see look better in lots of respects.

But having no expertise in the field I may have missed something in the report, or there might be heavy considerations against them which I am not aware of.

LNG has happened and will continue, I don't see a shift to ammonia.

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