Image of GM’s Hydrogen 3 fuel cell vehicle.
GM’s Hydrogen 3 fuel cell vehicle uses liquid hydrogen as fuel. The high cost of fuel cells is one reason that there are only a few thousand vehicles running on hydrogen fuel currently on U.S. roads. (Photo courtesy of U.S. Department of Energy)

Fuel cells generate electricity directly from hydrogen and oxygen and produce only water vapor as emissions. But most fuel cells are too expensive, inefficient, or both.

In a new approach, inspired by biology, a University of Wisconsin–Madison team has designed a fuel cell using cheaper materials and an organic compound that shuttles electrons and protons. In a traditional fuel cell, the electrons and protons from hydrogen are transported from one electrode to another, where they combine with oxygen to produce water. This process converts chemical energy into electricity. To generate a meaningful amount of charge in a short enough amount of time, a catalyst is needed to accelerate the reactions. Right now, the best catalyst on the market is platinum — but it comes with a high price tag. This is what makes the fuel cells expensive and is one reason why there are only a few thousand vehicles running on hydrogen fuel currently on U.S. roads.

The team’s solution was to pack a lower-cost metal, cobalt, into a reactor nearby, where the larger quantity of material doesn’t interfere with its performance. They then devised a strategy to shuttle electrons and protons back and forth from this reactor to the fuel cell.

The right vehicle for this transport proved to be an organic compound, called a quinone, that can carry two electrons and protons at a time. In this design, a quinone picks up these particles at the fuel cell electrode, transports them to the nearby reactor and then returns to the fuel cell to pick up more “passengers.”

Many quinones degrade into a tar-like substance after only a few round trips. The researchers, however, designed an ultra-stable quinone derivative. By modifying its structure, they drastically slowed down the deterioration of the quinone. In fact, the compounds they assembled last up to 5000 hours — a more than 100-fold increase in lifetime compared to previous quinone structures.

The next step is to bump up the performance of the quinone mediators, allowing them to shuttle electrons more effectively and produce more power. This advance would allow their design to match the performance of conventional fuel cells, but with a lower price tag. That could eventually be a boon for companies like Amazon and Home Depot that already use hydrogen fuel cells to drive forklifts in their warehouses.

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