(135d) Exploring Syntheses of Platinum-Based Ordered Intermetallic Nanoparticles

PtPb ordered intermetallics have been identified at the CFCI as candidates for anode electrocatalysts in fuel cells. Synthesis of PtPb nanoparticles by co-reduction of Pt and Pb compounds is being investigated. The initial reaction scheme revealed definite trends in particle domain size with reactant concentration, stirring time, and reaction temperature.To understand these observations (especially the failure of nanoparticles to crystallize at room temperature), the effects of the precursors' organic ligands were investigated. Compounds with ligands exhibiting a lower affinity for platinum were studied. Platinum acetylacetonate was chosen as an ideal precursor due to these ligand considerations and since it satisfies the solubility requirements: high and comparable to the lead precursor in solvent systems compatible with the reducing agent, sodium napthalide. Interesting trends, contrary to expectations, were observed when precursors were injected into a reducing agent solution at high temperatures. SEM imaging confirmed presence of organic groups on the nanoparticles and evidence of morphological changes in the nanoparticles with increasing reaction temperature. A definite relationship between domain size and extent of observed residue (organic material and sodium) present on the particles could be established. Room temperature crystallization of PtPb nanoparticles was also possible by varying post-reaction solvent removal technique. Electrochemical activity of the nanoparticles was also much higher than for nanoparticles synthesized by previous reaction schemes.Developing a universal platinum precursor that can be used for successful synthesis of nanoparticles of any Pt-based ordered intermetallic is vital for future development of these materials ? an promising class of compounds for anode electrocatalysis in fuel cells. Our future endeavors thus include exploring the effectiveness of platinum acetylacetonate in synthesizing other platinum based intermetallics.