A new combination of nanoparticles and graphene results in a more durable catalytic material for fuel cells. The catalytic material is not only hardier but more chemically active as well. The researchers are confident the results will help improve fuel cell design. Chemist, and all-around nice guy, Jun Liu and his colleagues at the Department of Energy's Pacific Northwest National Laboratory, Princeton University in Princeton, N.J., and Washington State University in Pullman, Wash., combined graphene, a one-atom-thick honeycomb of carbon with handy electrical and structural properties, with metal oxide nanoparticles to stabilize a fuel cell catalyst and make it better available to do its job. The centerpiece of the fuel cell is the chemical catalyst, usually a metal such as platinum, sitting on a support that is often made of carbon. A good supporting material spreads the platinum evenly over its surface to maximize the surface area with which it can attack gas molecules. It is also electrically conductive. Fuel cell developers most commonly use black carbon but platinum atoms tend to clump on such carbon. In addition, water can degrade the carbon away. Another support option is metal oxides (think rust) but what metal oxides make up for in stability and catalyst dispersion, they lose in conductivity and ease of synthesis. As a carbon support, Liu and his colleagues thought graphene intriguing. The honeycomb lattice of graphene is porous, electrically conductive and affords a lot of room for platinum atoms to work. First, the team crystallized nanoparticles of the metal oxide known as indium tin oxide (or ITO) directly onto specially treated graphene. Then they added platinum nanoparticles to the graphene-ITO and tested the materials.
The team viewed the materials under high-resolution microscopes. The images showed that without ITO, platinum atoms clumped up on the graphene surface. But with ITO, the platinum spread out nicely. Those images also showed catalytic platinum wedged between the nanoparticles and the graphene surface, with the nanoparticles partially sitting on the platinum like a paperweight. The team tested how well the new material stands up to repeated usage by artificially aging it. After aging, the tripartite material proved to be three times as durable as the lone catalyst on graphene and twice as durable as on commonly used activated carbon. Corrosion tests revealed that the triple threat was more resistant than the other materials tested as well. The team is now incorporating the platinum-ITO-graphene material into experimental fuel cells to determine how well it works under real world conditions and how long it lasts.
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