Technological Breakthrough Allows Seamless Conversion of Ammonia to Green Hydrogen

Researchers leverage renewable electricity for widespread, distributed hydrogen fuel production.

Northwestern University researchers have developed a highly effective, environmentally friendly method for converting ammonia into hydrogen. Outlined in a recent publication in the journal Joule, the new technique is a major step forward for enabling a zero-pollution, hydrogen-fueled economy.

The idea of using ammonia as a carrier for hydrogen delivery has gained traction in recent years because ammonia is much easier to liquify than hydrogen and is therefore much easier to store and transport. Northwestern’s technological breakthrough overcomes several existing barriers to the production of clean hydrogen from ammonia.

“The bane for hydrogen fuel cells has been the lack of delivery infrastructure,” said Sossina Haile, lead author of the study. “It’s difficult and expensive to transport hydrogen, but an extensive ammonia delivery system already exists. There are pipelines for it. We deliver lots of ammonia all over the world for fertilizer. If you give us ammonia, the electrochemical systems we developed can convert that ammonia to fuel-cell-ready, clean hydrogen on-site at any scale.” 

Haile is Walter P. Murphy Professor of materials science and engineering at Northwestern’s McCormick School of Engineering with additional appointments in applied physics and chemistry. She also is co-director at the University-wide Institute for Sustainability and Energy at Northwestern. 

In the study, Haile and her research team report they are able to conduct the ammonia-to-hydrogen conversion using renewable electricity instead of fossil-fueled thermal energy because the process functions at much lower temperatures than traditional methods (250 degrees Celsius as opposed to 500 to 600 degrees Celsius). Second, the new technique generates pure hydrogen that does not need to be separated from any unreacted ammonia or other products. Third, the process is efficient because all of the electrical current supplied to the device directly produces hydrogen, without any loss to parasitic reactions. As an added advantage, because the hydrogen produced is pure, it can be directly pressurized for high-density storage by simply ramping up the electrical power.

To accomplish the conversion, the researchers built a unique electrochemical cell with a proton-conducting membrane and integrated it with an ammonia-splitting catalyst.

“The ammonia first encounters the catalyst that splits it into nitrogen and hydrogen,” Haile said. “That hydrogen gets immediately converted into protons, which are then electrically driven across the proton-conducting membrane in our electrochemical cell. By continually pulling off the hydrogen, we drive the reaction to go further than it would otherwise. This is known as Le Chatelier’s principle. By removing one of the products of the ammonia-splitting reaction — namely the hydrogen — we push the reaction forward, beyond what the ammonia-splitting catalyst can do alone.”

The hydrogen generated from the ammonia splitting then can be used in a fuel cell. Like batteries, fuel cells produce electric power by converting energy produced by chemical reactions. Unlike batteries, fuel cells can produce electricity as long as fuel is supplied, never losing their charge. Hydrogen is a clean fuel that, when consumed in a fuel cell, produces water as its only byproduct. This stands in contrast with fossil fuels, which produce climate-changing greenhouse gases such as carbon dioxide, methane and nitrous oxide.

Haile predicts that the new technology could be especially transformative in the transportation sector. In 2018, the movement of people and goods by cars, trucks, trains, ships, airplanes and other vehicles accounted for 28% of greenhouse gas emissions in the U.S. — more than any other economic sector, according to the Environmental Protection Agency.

“Battery-powered vehicles are great, but there’s certainly a question of range and material supply,” Haile said. “Converting ammonia to hydrogen on-site and in a distributed way would allow you to drive into a fueling station and get pressurized hydrogen for your car. There’s also a growing interest for hydrogen fuel cells for the aviation industry because batteries are so heavy.”

Haile and her team have made major advances in the area of fuel cells over the years. As a next step in their work, they are exploring new methods to produce ammonia in an environmentally friendly way.

Reference: “Solid Acid Electrochemical Cell for the Production of Hydrogen from Ammonia” by Dae-Kwang Lim, Austin B. Plymill, Haemin Paik, Xin Qian, Strahinja Zecevic, Calum R.I. Chisholm and Sossina M. Haile, 3 November 2020, Joule.
DOI: 10.1016/j.joule.2020.10.006

The research was supported by the Advanced Research Projects Agency-Energy (ARPA-E) at the U.S. Department of Energy (award number DE-AR0000813) and the National Science Foundation (grants NSF ECCS-1542205 and NSF DMR-1720139).

Other authors include researchers from SAFCell, an energy startup company based in California.

EnergyGreen EnergyHydrogenNorthwestern University
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  • Joe Milosch

    Great technological advance. Ah… to be young again and actively involved in all this new hydrogen technology. 🙂 Oh well, I’m just glad to see that it is starting to gain fruition.

  • Bob

    Ammonia production is a very energy-intensive process, consuming 1 to 2% of global energy, 3% of global carbon emissions, and 3 to 5% of natural gas consumption.
    So much energy loss getting “green” via H2/fuel cells!

  • Kafantaris George

    There is no fight with the fossil fuels. Indeed, the only way for us to effectively fight climate change is with the help of fossil fuels. Renewable energy from the sun and the wind are simply not enough. They are not even enough to satisfy our increasing appetite for power.
    Nuclear and hydro can certainly help but even these two are not enough. The only way we can make up for the balance of the power we need is with blue hydrogen that is made from natural gas using carbon capture and storage. There is lots and lots of natural gas all over the world to help us do this, including right here in the United States and nearby Canada. Aside from blue hydrogen, we can also make ammonia to power airplanes and ships; and to make fertilizer and steel. Indeed, ammonia will become the medium to transport the hydrogen itself since it holds 150% more hydrogen than even liquid hydrogen. So yes, fossil fuels are the necessary partners in our Herculean efforts at decarbonization — and integral ones too — if we are to make a dent on climate change. And we must make a dent — or else.

    • John Jakson

      Wow, so fossil energy releases CO2, giving energy and other good stuff. Then we collect that CO2 and turn it back into new fuel. Where exactly does the energy come from to pull the CO2 from the atmosphere or oceans? I know the answer to that one, more fossil energy of course.

      In another world and a decade ago, the US Navy actually built hardware to extract CO2 from the oceans using nuclear electricity from a carrier. The idea was to make jet fuel for the carrier aircraft from water, CO2, H2 etc to avoid carrying fuel around the world. Actually that was the plan, instead the hardware ran on dry land from grid power but it did show the energy needed to pull CO2 out of sea water with an AC like battery cell without altering the resulting sea water chemistry. IIRC sea water holds about 140 times more CO2 than the air,so that is where you should pull it from.

      The result was that the energy needed to do this was about the same amount of energy generated from the fossil plant that put the same amount of CO2 into the atmosphere in the first place. In other words they demonstrated the folly of using fossil energy with zero carbon effect, essentially sub unity. It can’t be done. The nuclear reactor though could have done the job and been carbon negative.

      And of course nuclear could power the world, there is at least 500kg of uranium in the worlds oceans for each of 10B people, so enough to last the world quite a few centuries. Throw in thorium, 4 times as much again, plus it produces rare earths with it. This would be done with MSR or sodium cooled breeders…. And now they can be designed to not only load follow but can produce power on demand as long as total daily output matches constant thermal output times eff factor about 50%. See Moltex or see Terrapower.

  • xABBAAA

    … Cool…

  • John Jakson

    So Nova and David Pogue described the Haber Bosch process pretty well on Beyond the Elements on PBS show a few weeks ago.

    So it takes a considerable amount of energy to break the N2 bond and combine it with H2 to make ammonia NH3. Now we want to undo that by adding more renewable energy to break what we just made back into H2 and N2. What gives? Just to have a different way of transporting H2.

    These H2 from ammonia folks could have just asked their ammonia supllier where they got the H2 from, yep that came from steam reforming nat gas.

    So the future of hydrogen transport means
    1) steam reform nat gas into H2 and emit CO2, water, then…
    2) use more fossil energy to Haber Bosch the H2 with N2 into NH3, then…
    3) use more energy to break the NH3 back into H2 and N2, then…
    4) use more energy to liquify the H2, then
    5) use delivered H2 in a fuel cell with platinum catalyst from where exactly (Russia?)

    It never ceases to amaze how many energy processes can be stacked to make the wet dream happen in the name of all things green, or is it blue energy today.

  • John Jakson

    Yes ammonia fertilizer is delivered all over the world and sometimes even left in docks, like in Beirut, what could go wrong did go wrong.

    As a kid I grew up near one of these nitrate plants, dirty secret was if it could ever blow up how close to London would the explosion be. We were of course left completely in the dark about the dangers of N2 compounds.