A research team led by McCormick Prof. Sossina Haile recently discovered an environmentally friendly way to convert ammonia into pure hydrogen, which can be used as environmentally-friendly fuel for cars. Hydrogen-fuelled cars have a greater range than their battery counterparts and do not need to be recharged.

This new, carbon-free method can be carried out using entirely green energy because the conversion happens at only 250 degrees Celsius, hundreds of degrees lower than traditional methods. In addition, it generates clean hydrogen that does not need to be separated from added impurities like ammonia, a gas composed of hydrogen and nitrogen.

The discovery involves an electrochemical cell that integrates a conducting membrane with an ammonia-splitting catalyst, enabling the separation of pure hydrogen from ammonia.

“It was always a good idea to have hydrogen be your energy source or energy carrier rather than gasoline, for example, because when you combine gasoline with oxygen, you produce (carbon dioxide),” Haile said. “So wouldn’t it be great if you could do all of this with hydrogen?”

Haile said hydrogen has always been a desirable fuel source but, until recently, had not gained much traction because of the difficulties associated in storing and transporting it.

Haile and her team’s new method has made it possible for ammonia to serve as a carrier for hydrogen, which could potentially be a fuel source for everyday vehicles.

“It’s still the case that you’re going to get better range with a hydrogen fuel cell vehicle than you do with a battery,” Haile said. “Although batteries are getting better, you don’t have to recharge (a hydrogen-powered car). It’s refueling in the same way that you would refuel a normal car.”

Haemin Paik, a paper author and postdoctoral fellow at Massachusetts Institute of Technology, said this discovery might change the hydrogen economy and help drive innovation in the green energy sector, because there are already well-established ammonia transport infrastructures to use.

Haile, who is also co-director of the Northwestern Institute for Sustainability and Energy, said the research has already attracted interest at the industrial level from manufacturers producing hydrogen-fueled cars. She partially attributed this to the current political climate and an increased interest in sustainability and climate change.

Calum Chrisholm, another paper author, has been manufacturing fuel cells very similar to the design of the conversion cells in her team’s recent research, Haile said. The similarity of the components provides a quick path to commercialization for Haile’s technique.

Another highlight of this discovery is its efficient nature, said Paik, who worked with Haile as a Northwestern visiting scholar from 2015-19. Traditional approaches use high amounts of electricity for a lower volume of hydrogen output, but this technique ensures no electrical energy is lost to parasitic reactions.

“It has much higher efficiency than other technology for converting ammonia to hydrogen and a much lower temperature,” Paik said.

Looking forward, Haile said her goal is to find a way to generate green ammonia that doesn’t use natural gas in its manufacturing, so the entire process can be eco-friendly. As of now, ammonia production typically relies on natural gas, she said.

“How do we make (the process) completely carbon-free from beginning to end?” Haile said. “We’ve done one half of it, so now we want to do the other half.”

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