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The researchers at Cornell University in New York state set out to tackle the problem of high fuel-cell cost, which they said remains ‘prohibitively expensive’ because of a reliance on platinum and other precious metals to keep the electrochemical reactions running efficiently.
Hydrogen fuel cells generate electricity with only water and a small amount of heat as their by-products. A critical part of the fuel cell is the oxygen reduction reaction (ORR), an infamously slow process that is traditionally sped up by platinum and other precious metals.
With alkaline fuel cells gaining prominence, the researchers investigated the possibility that other, less expensive metals – previously ruled out for their vulnerability to acidic environments – might replace platinum.
Professor Héctor D. Abruña and his team set out to engineer an inexpensive material fit for an alkaline fuel cell, that would conduct electricity and catalyse the ORR reaction just as efficiently as platinum.
Transition metal nitrides (TMNs) were an obvious choice, Professor Abruña said. A class of compounds derived from cobalt, manganese, iron and other transition metals, TMNs conduct electricity and, when exposed to air, tend to form a thin oxygen-based outer shell that provides a perfect surface for catalysing chemical reactions. After synthesising a family of TMNs with conductive nitride cores and reactive oxide shells, the team tested each candidate catalyst in a model hydrogen fuel cell.
The cobalt nitride catalyst was “the clear winner,” Professor Abruña said, with near-identical efficiency to platinum while costing 475 times less. “These less-expensive metals will enable wider deployment of hydrogen fuel cells,” he said. “They will push us away from fossil fuels and toward renewable energy sources.”
Those savings could finally bring hydrogen fuel cells into the mainstream, a research announcement claimed. Affordable fuel cells could replace combustion engines and car batteries with a sustainable alternative that wastes as little as 10% of the energy that goes into making it run. By comparison, a typical car engine wastes about 75% of its energy.
“Hydrogen fuel cells are enormously powerful, enabling you to run at an efficiency that simply does not exist for more traditional engines,” Abruña said. “People recognise that fuel cells are the way to go. The trick is designing stable and affordable catalysts that make it all possible.”
Funding for the research was provided in part by the Centre for Alkaline Based Energy Solutions, an Energy Frontier Research Centre supported by the US Department of Energy.
The findings were published in Science Advances.
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