(Pacific Northwest National Laboratory)
A new combination of nanoparticles and graphene results in a more durable catalytic material for fuel cells, according to a new report. The catalytic material is not only hardier but more chemically active as well.
The centerpiece of a fuel cell is the chemical catalyst, such as platinum, sitting on a support that is often made of carbon. 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, but what metal oxides make up for in stability and catalyst dispersion, they lose in conductivity and ease of synthesis. Researchers have begun to explore metal oxides in conjunction with carbon materials to get the best of both worlds.
As a carbon support, graphene intriguing. The honeycomb lattice of graphene is porous, electrically conductive and affords a lot of room for platinum atoms to work. In the new work, the team crystallized nanoparticles of indium tin oxide (ITO) directly onto specially treated graphene. Then they added platinum nanoparticles to the graphene-ITO and tested the materials.
Transmission electron microscopy images showed that without ITO, platinum atoms clumped up on the graphene surface. But in the presence of ITO, the platinum spread out nicely. The images also showed catalytic platinum wedged between the nanoparticles and the graphene surface, with the nanoparticles partially sitting on the platinum like a paperweight.
Theoretical calculations of molecular interactions between the graphene, platinum and ITO indicated that the threesome was more stable than the metal oxide alone on graphene or the catalyst alone on graphene. In experiments on how well the materials break down oxygen as they would in a fuel cell, the new material showed a 40% improvement over the catalyst alone on graphene or the catalyst alone on other carbon-based supports such as activated carbon. Aging tests showed that the tripartite material was three times as durable as the lone catalyst on graphene and twice as durable as on commonly used activated carbon.
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.
Stabilization of Electrocatalytic Metal Nanoparticles at Metal−Metal Oxide−Graphene Triple Junction Points
J. Am. Chem. Soc., Article ASAP, DOI: 10.1021/ja107719u
Publication Date (Web): February 8, 2011
Gopal R. Rao, Ph.D.
Web Science Editor
Materials Research Society (MRS)