New research shows that formic acid could be used as a safe, easy-to-transport source of hydrogen for fuel cells. Matthias Beller and his colleagues at the Leibniz Institute of Catalysis, in Rostock, Germany, have found a way to convert formic acid, a common preservative and antibacterial agent, into hydrogen gas at low temperatures.
While hydrogen produced using this method might not find use in fuel-cell vehicles anytime soon, the researchers say that the process could produce sufficient quantities for micro fuel cells that power portable electronic devices, such as cell phones and laptops.
The challenge of producing, storing, and transporting hydrogen affordably has kept fuel cells from becoming popular. Instead of transporting hydrogen gas, it is more practical to have a hydrogen-containing material that can be broken down to generate the gas where it is needed. Currently, methane and methanol top the list of hydrogen sources for fuel-cell vehicles. They are typically broken down via steam reforming, which requires temperatures of more than 200 °C and a reforming unit.
Processes that work at cooler temperatures would not need a reformer or much energy, and therefore could be more suitable for producing hydrogen for smaller fuel cells that power portable electronic devices. The new process, which Beller and his colleagues outline in Angewandte Chemie, works at temperatures of 26 to 40 °C. The researchers mix formic acid with amines and expose the mixture to a ruthenium-based catalyst, which breaks down the acid into hydrogen and carbon dioxide.
“The advantage of formic acid is [that] it’s a liquid … and is relatively easily handled,” Beller says. While the pure acid is corrosive, the mixture of the acid with amines is benign, he says.
Formic acid can also be used directly in a fuel cell. That might be easier because it saves the extra step of first converting it into hydrogen. Tekion, based in Burnaby, Canada, is working with Germany-based chemical giant BASF, the largest producer of formic acid, to commercialize a fuel cell that uses formic acid directly. Tekion, which does not have a product on the market yet, claims that its formic-acid fuel cells are smaller and less complex than direct methanol fuel cells. But direct formic-acid fuel cells have the same drawback that makes methanol fuel cells expensive: both technologies are less efficient than hydrogen fuel cells.
Beller points out that using formic acid to make hydrogen also has drawbacks. Compared with methane and methanol, formic acid has much less hydrogen. If you use all the hydrogen in a kilogram of methanol, you get 4.19 kilowatt-hours of energy, while the hydrogen in a kilogram of formic acid gives 1.45 kilowatt-hours.
That could make formic acid a more expensive hydrogen source than methane or methanol. At the same time, the process takes less energy than steam reforming, and with better catalysts, the researchers could make costs more favorable, Beller says.
Formic acid could have a shot at reaching the portable electronics fuel-cell market, suggests Richard Farmer, who leads the hydrogen production and delivery team at the Department of Energy’s Energy Efficiency and Renewable Energy Laboratory.
To make large quantities of hydrogen for fuel-cell vehicles, however, the process would have to compare with the current benchmark: steam-methane reforming. With a small steam-reformer unit at a fueling station, Farmer says, “we’ve hit our near-term target of three dollars per kilogram [of hydrogen], untaxed but delivered.”
Beller and his colleagues may have a long way to go to produce sufficient amounts of cheap hydrogen for vehicles, but they are already discussing their technology with two German automotive companies. They are also working with some engineers to build a small prototype model car that uses the technology and that should be ready in two months. But in the short term, Beller says, the researchers consider formic acid a fuel source for portable electronics. “We don’t aim currently for large use in cars–this does not make sense.”
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