Section: Complex Oxides

Nanostructured Systems

Nanostructured materials could revolutionize electrochemical devices such as fuel cells, batteries, and supercapacitors.  An affordable and scalable approach to nanostructure materials is with block copolymers (Fig 1).  Block copolymers are large molecules with chemically disimilar regions such as those depicted red and yellow.  We can take advantage of these disimilar regions by selectively encorporating nanoparticles into just one of the polymer's blocks.  We found that varying the particle to polymer ratio enabled us to achieve many different ordered nanostructures (Fig 1 bottom).  The polymer may be removed from these nanostructures leaving behind open pores.  The resulting porous materials have very high surface areas which makes them of great interest for electrochemical devices.

Fig 1. Block copolymers can control the spatial organization of nanoparticles.  By varying the particle to polymer ratio numerous highly ordered nanostructures may be achieved. (M. Templin, U. Wiesner et al. Science 278 (1997) 1795)

We have taken this approach further by nano-structuring materials which are useful in high performance fuel cell electrodes.  Niobia is one of the very few materials which is stable in PEM fuel cells and is a promising support material for the latest platinum-lead catalysts.  We developed a simple "one-pot" procedure to create nano-porous niobia with platinum-lead nanoparticles decorating the pores (Fig 2).  These nanostructured materials were 4 times more active at formic acid oxidation than the best previously reported platinum-lead catalyst on carbon!   The research at the Energy Materials Center at Cornell is paving the way to the best energy materials.

Fig 2. Schematic "one-pot" procedure to use block copolymers for the fabrication of nanoporous materials decorated with catalyst nanoparticles.  The results of this procedure on shown on the right.  (M. Christopher Orilall, Futoshi Matsumoto, Qin Zhou, Hiroaki Sai, Hctor D. Abrua, Francis J. DiSalvo, Ulrich Wiesner. Journal of the American Chemical Society 2009 131 (26), 9389-9395 )