| Polymer Electrolyte Membrane Fuel cells are electrochemical devices that convert energy stored in chemical bonds of fuel (hydrogen gas, methanol, etc.) directly into electrical energy with high theoretical efficiency. The major challenges are the slow oxygen reduction reaction kinetics, requiring a significant amount of Pt catalyst to achieve significant current densities. Finding catalysts, which are more active and cheaper than Pt, as well as being stable under cathodic conditions will be key to making this technology more economically attractive. First, a method was developed to synthesize ordered intermetallic nanoparticles in the 4-6 nm size range. The synthetic method used was a modified solution phase coreduction method, which is able to synthesize ordered intermetallic nanoparticles in the 4-6 nm size range. This method was used to form carbon supported, ordered tetragonal Pt2MM' (M and M' are = Fe, Co, or Ni) nanoparticles. After extensive characterization and electrochemical measurements, it was found that ordered tetragonal Pt2FeNi/C catalyst showed the highest activity roughly four times as efficient as pure platinum, with a half-wave potential roughly 30 mV more positive than the Pt/C standard. The ordered tetragonal material also showed high stability under cathodic conditions, losing roughly 10% of the 3d element after 2000 cycles (from 0.05 -- 1.10 V at 50 mV/s). |
