Platinum-graphene fuel cell catalyst achieves unprecedented performance

A recent study published by researchers at the Georgia Institute of Technology shows that a platinum film supported by graphene with only two atoms thick can give fuel cell catalysts unprecedented catalytic activity and lifetime.

Platinum is one of the most commonly used catalysts in fuel cells because it can effectively promote redox reactions. But its high cost has prompted researchers to find ways to use less platinum while maintaining the same catalytic activity.

Faisal Alamgir, an associate professor at the Georgia Institute of Technology, said: "The production of fuel cells with platinum catalysts always has to pay a certain initial cost, and keep the cost as low as possible. It ’s important. But the actual cost of the fuel cell system is calculated based on the system ’s usage time, which is a matter of durability. "

Alamgir said: "Recently there is a trend to use platinum-free catalytic systems, but the problem is that there is currently no system that can simultaneously achieve the catalytic activity and durability of platinum."

Researchers at Georgia Institute of Technology have tried different strategies. The study was published in the journal "Advanced Functional Materials" on September 18 and was supported by the National Science Foundation. They described several systems using atomic-scale thin-film platinum supported by a graphene layer-effectively maximized It can be used to catalyze the surface area of ​​platinum and requires only a small amount of precious metals.

Most platinum-based catalytic systems use metal nanoparticles to chemically bond with the support surface. On the support surface, the surface atoms of the particles undertake most of the catalytic work, and the catalytic potential of the atoms below the surface has never been like the surface atoms. That's fully utilized (if any).

In addition, the researchers also found that at least two atoms thick of the new platinum film is superior to nano-platinum in terms of dissociation energy, and dissociation energy is a measure of the energy cost of a surface platinum atom. This measurement indicates that these films may create a more durable catalytic system.

To prepare the atomic thin film, the researchers used a method called "electrochemical atomic layer deposition" to grow a single-layer platinum film on the graphene layer to create a sample containing one, two, or three layers of atoms. The researchers then tested the dissociation energy of these samples and compared the results with the energy of individual platinum atoms on graphene and the common structure of platinum nanoparticles used in catalysts.

"The core of this work is whether the combination of metals and covalent bonds makes it possible for the platinum atoms in the platinum-graphene combination to be more stable than the bulk platinum catalysts bonded with metal bonds," Seung, associate professor at the School of Materials Science and Engineering Soon Jang said.

The researchers found that the bond between the adjacent platinum atoms in the film and the bond between the film and the graphene layer provide a reinforcement for the entire system. This is especially true on two-atom-thick platinum films.

Alamgir said that metal thin films usually below a certain thickness are unstable because the bonds between them are not oriented, and they tend to roll each other to form particles. But graphene is not the case, it is stable in two-dimensional form, even as thick as one atom, because there are strong covalent bonds between adjacent atoms. Therefore, this new catalytic system can use the orientation bond of graphene to support a layer of platinum film with atomic thickness.

Future research will include further testing the behavior of these films in a catalytic environment. Researchers discovered in an early study of graphene-platinum films that this material exhibited similar behavior in catalytic reactions, regardless of which side—graphene or platinum—was exposed to the active surface.

Alamgir said that in this structure, graphene has not become an independent face of platinum. They can work together. Therefore, we believe that if you expose the graphene side, you will get the same catalytic activity, so that you can further protect platinum, potentially improving durability.

(Originally from: Daily Science China New Energy Network Synthesis)

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