PITA Fiscal Year 2007 Projects

Nanotechnology

Novel Nanostructured Non-Noble Metal Based Catalysts and Catalyst Supports for Proton Exchange Membrane Fuel Cells (PEMFCs)
Electrocatalytic studies reported to date have shown that the equi-molar composition of Pt-Ru (Pt:Ru = 1:1) exhibits the best electrocatalytic activity towards direct oxidation of methanol. Johnson Matthey (JM) catalysts corresponding to this composition has hence been considered as the standard for gauging the activity of electrocatalysts. However, recent PITA supported studies conducted in the PI’s laboratory indicate that the addition of non-noble metal additives such as titanium (Ti), and nickel (Ni) to Pt and Ru exhibit promising electrochemical activity matching the catalytic activity of the original equimolar Pt-Ru composition. These results suggest the potential of significantly reducing the noble metal content corresponding to the equi-molar composition of Pt-Ru. The novel sol-gel process developed in the PI’s laboratory for synthesizing the equi-molar composition of Pt-Ru will be extended and modified to synthesize the Ni-Pt-Ti-Ru catalysts, specifically (Ni31Ti13Pt33Ru23) using non-halide precursors. The metal carboxylate precursors will be hydrolyzed and complexed using suitable chelating agents to generate a molecularly coordinated complexed gel containing varying amounts of Ni and Ti to identify compositions that will yield the most optimum electrocatalytic activity matching the Pt:Ru(1:1) composition and further optimizing the compositions to identify ratios that even exceed the performance of JM. The gel precursors will be subjected to careful heat treatment in an inert atmosphere substituted with oxygen to eliminate carbon without inducing oxidation of the precursor. Thermal treatment of the as-prepared precursors in various atmospheres will result in the generation of single phase solid solutions of Pt-Ru alloy type structures containing Ni and Ti phases. The resultant catalysts will likely exhibit surface areas in the 120-160 m2/g range. Furthermore, it is known that carbon supports on which the catalysts are traditionally supported are unstable and susceptible to corrosion and oxidation. Our results have shown that transition metal nitrides, particularly, CrN are very stable to corrosion and oxidation resistance. High surface forms of these nitrides will therefore be generated on which these catalysts will be synthesized by coating the nanoparticles with the gels followed by careful heat treatment as discussed above to result in high surface area supported catalysts.

These novel sol-gel derived catalysts and catalysts supported on the transition metal nitride will be characterized for structure, phase and composition using X-ray diffraction, thermal analysis and high resolution transmission electron microscopy. Electrochemical characterization of the catalysts will also be conducted using a 3-electrode half cell assembly. The surface area of the synthesized catalysts will be measured, while suitable samples will be characterized at CMU and promising samples will be sent to DuPont for conducting systematic electrochemical tests in full fuel cell configurations. Collaborations will also be sought with Professor Klein at Lehigh University complementing the effort on embedding catalyst particles in polymeric micelles.