Jul 17, 2012
Metals anchor platinum to graphene
Graphene is the strongest and thinnest material in the world and has the highest electrical and thermal conductivity among all materials. It is a two dimensional, single atomic layer of carbon arranged in a honeycomb structure and the building block of many advanced carbon structures.
In fuel cells and lithium–air batteries, graphene or other forms of carbon are used to carry electrons to platinum nanoparticles that are used as a catalyst. However, platinum does not adhere to the graphene surface strongly, causing a decrease in performance during the lifetime of the device. It is an important challenge to find a suitable dopant that effectively enhances the metal–carbon interfacial strength without deteriorating graphene's physical and mechanical properties. In J. Phys.: Condens. Matter 24 225003, first principles calculations based on the spin-polarized density functional theory (DFT) were used to systematically screen several metallic elements in terms of their ability to modify the graphene surface and influence Pt/graphene interface strength.
It was revealed that metals with unfilled d orbitals can increase the Pt/graphene interface strength from 0.009 J/m2 to above 0.5 J/m2. The total Pt/graphene interface strength and, hence, the anchoring effect of the adatom was shown to be controlled by the carbon–metal adatom bond strength. Among all elements, Ir, Os, Ru, Rh and Re were identified as the most effective modifications when sandwiched between Pt and graphene, since these elements were found to distribute their electronic charges evenly between Pt and graphene surfaces.
The systematic study provides a useful procedure for a computational guided materials design. The metallic elements that distribute their electrons evenly between Pt and graphene efficiently act as a bridge to anchor the Pt to graphene without sacrificing electron conductivity. The results can be used not only to design fuel cells and lithium–air batteries with an improved performance and durability, but also in applications where a strong adhesion between Pt and graphene is desired.
About the author
This work was jointly performed by a research team working at the University of Windsor, Ontario, Canada and the General Motors R&D Center, Warren, MI, USA. Sen is a research assistant and a PhD student at the University of Windsor. Qi is a staff research scientist at the General Motors R&D Center and an adjunct professor at the University of Windsor. Alpas is a professor of Materials Science and Engineering at the University of Windsor and NSERC/GM Industrial Research Chair. The main calculations were carried out using the resources in SHARCNET (Shared Hierarchical Academic Research Computing Network) of Canada. This work was supported by the NSERC (Natural Sciences and Engineering Research Council of Canada) and General Motors.