Sodium fuel cell could power an electric airplane

Hydrogen fuel cells, which power some electric cars, pack far more energy per weight than lithium-ion batteries. The devices also show promise for decarbonizing aviation, shipping, and trucking. But hydrogen fuel requires compression or cryogenic temperatures for storage.

A new sodium-air fuel cell could be a more practical and sustainable power source (Joule 2025, DOI: 10.1016/j.joule.2025.101962). The fuel cell has an energy density of over 1,000 W h/kg, roughly four times that of typical electric vehicle batteries, which is the benchmark “that’s recognized as necessary to electrify aviation and other hard-to-decarbonize transport sectors,” says Yet-Ming Chiang, a materials scientist and battery specialist at the Massachusetts Institute of Technology who led the study.

The device could, in theory, propel a single-aisle 50–100 passenger airplane—a size typically used for regional flights—for more than 320 km, Chiang says. And as it discharges, it produces sodium hydroxide (NaOH), which you could use to capture carbon dioxide or sell to the chemical industry, he says.

Batteries and fuel cells produce electricity via electrochemical reactions. But while rechargeable batteries contain chemical components in a sealed package and produce electricity via reversible reactions, fuel cells rely on an external fuel source, so instead of recharging they need a refill of fuel.

Chiang and his colleagues were inspired by metal-air batteries, in which redox reactions between a solid metal anode and oxygen from air at the cathode generate electricity. But these batteries aren’t rechargeable, and making the reactions reversible requires purifying the oxygen, which adds hefty, costly equipment.

So the researchers crafted a fuel cell based on low-cost sodium-air chemistry. The device has liquid sodium metal at the anode, and the researchers humidify the air that runs past the cathode. Sodium reacts with oxygen and water to produce NaOH, which liquefies and drips off the cathode. After the reactions consume the liquid sodium, you would simply swap out the fuel cell or its fuel tank for a full one, Chiang says.

The NaOH could be ejected into the atmosphere to react with CO₂ and form sodium carbonate. The added carbon capture value should make the system cost competitive with green hydrogen and sustainable aviation fuels and cheaper than green ammonia, the team’s analysis shows. “We’re starting with sodium in its least stable state,” Chiang says. “Sodium metal naturally wants to go to oxide, then hydroxide, then carbonate. So we’re going with that flow.”

Scaling up would require large-scale production of sodium metal, but there is historic precedent for that in the US, he says. In the 1970s, the US had a manufacturing capacity of over 200,000 tons of sodium metal per year, with E. I. du Pont de Nemours and Company being the largest producer.

Linda Nazar, a professor of chemistry at the University of Waterloo, says that the temperatures needed to keep sodium in the liquid state—sodium’s melting point is 98 °C—might pose a concern. “But liquid sodium is used as the anode in sodium-sulfur batteries that run at higher temperatures, and there have been relatively few problems.” The upsides of the device are its excellent energy characteristics, use of low-cost sodium, and the potential for capturing CO₂, she says. “In short, it’s a clever idea!”