Synthesis of Nanoparticles of complex materials
The CFCI began with the discovery of impurity tolerant anode catalysts. These were ordered intermetallic compounds, such as PtPb (see figure below) and PtBi. These ordered compounds are structurally and electronically very different than alloys (sometimes called solid solutions). This difference is very clear when the structure of the alloy Pt0.5Ru0.5 is compared to that of PtPb.
Since there are approximately 100,000 known intermetallic compounds (binary, ternary and quaternary), and many more yet to be discovered, it became apparent that we could not search for catalytic activity in this family by making compounds one at a time. That would take way too long!
Hence, CFCI now has a large effort in combinatorial searching and screening for novel catalysts, both intermetallics for anode catalysts and other materials for cathode catalysts9, 10. The combinatorial method prepares thin films with large composition gradients. However, the catalysts must be in nanoparticle form if they are to be used in fuel cells. Thus when a new composition is found to be a potentially superior catalyst, we need to make this composition in nanoparticle form. Each nanoparticle needs to have the same composition and structure.
Our approach to preparing nanoparticles
is to reduce metal
precursors in solution under the proper conditions to obtain
homogeneous
nanoparticles with diameters on the order of 5 nm. These particles must
also
eventually be bound to conducting catalyst supports. Since it is
possible that
the catalytic behavior of the nanoparticles is different of bulk or
film forms
of the same material, we need to show the catalytic activity is at
least as
good as in the bulk (sometimes it is even better!).
Finally, if this research is very successful, the materials will need to be made available to fuel cell manufacturers on the many ton scale. We are collaborating with a local company, Primet Precision Materials, that has developed a proprietary technology to make nanoparticles on the ton scale by starting with bulk materials. CFCI researchers are working with Primet to evaluate the performance of the materials made by this process.
