Hydrogen does its bit for low-cost fuel-cell catalysts

Gang Wu (front and center) and his group. Photo: Douglas Levere, University at Buffalo.
Gang Wu (front and center) and his group. Photo: Douglas Levere, University at Buffalo.

To make fuel cells more affordable, researchers have spent decades searching for low-cost catalysts to replace the platinum and other expensive metals currently used. This has included experimenting with different combinations of three abundant and relatively cheap materials – iron, nitrogen and carbon.

Unfortunately, results thus far have been uneven. Researchers can make iron-nitrogen-carbon catalysts durable or efficient, but not both.

A new study ed by researchers at the University at Buffalo may offer a solution. In a paper in Nature Catalysis, the researchers report how adding hydrogen to the fabrication process creates a strong and effective catalyst that approaches the performance of platinum.

This discovery represents an important step toward helping fuel-cell technology live up to its potential as a pollution-free provider of electricity for cars, trucks, trains, airplanes and other heavy-duty vehicles.

“For years, the scientific community has struggled to balance this tradeoff,” explains Gang Wu, professor in the Department of Chemical and Biological Engineering and corresponding author of the paper. “We can make low-cost that are effective but degrade too easily. Or we’ve made them very stable, but their performance couldn’t match platinum. With this work, we’ve taken a step toward solving this problem.”

This work builds on previous research by Wu, in which he produced iron-nitrogen-carbon catalysts that, while durable, struggled to speed up important chemical reactions within fuel cells. The new study addressed this limitation by focusing on a fabrication process called pyrolysis, which involves using extremely hot temperatures to combine materials.

During pyrolysis, the researchers bonded four nitrogen atoms to the iron in a high-temperature chamber. They then embedded this material in a few layers of graphene, which is a tough, light and flexible form of carbon.

Usually, this process is conducted within a chamber featuring an inert gas, such as argon. But this time, the researchers also fed some hydrogen into the chamber to create a mixture comprising 90% argon and 10% hydrogen.

This meant they could more precisely control the makeup of the catalyst. Specifically, they were able to place two different iron-nitrogen-carbon compounds (one containing 10 carbon atoms, the other containing 12 carbon atoms) in positions that support durability and efficiency.

The resulting catalyst achieved an initial fuel-cell performance well beyond the US Department of Energy’s goal for 2025. It also proved more durable than most previous iron-nitrogen-carbon catalysts, approaching that of a typical low-platinum cathode used for fuel cells.

This story is adapted from material from the University at Buffalo, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.

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