Microplasma-based Synthesis of Nanostructured Pt

Platinum is an excellent catalyst for the oxygen reduction reaction (ORR: O2 + 4H+ + 4e- →2H2O) in a fuel cell, and nanostructured platinum films with particle sizes in the sub-10 nm range are attractive due to their high activity and efficient Pt utilization. In this work, nanostructured Pt and Pt-alloy films and nanoparticles were deposited on doped silicon (Si) and indium tin oxide (ITO) substrates under a variety of conditions using a novel microplasma jet spray deposition technique. Pt precursor (Pt (II) hexafluoroacetylacetonate - Pt(hfac)) was sublimed and fed to the plasma anode capillary tube using an Ar carrier, with deposition pressures ranging from 10-760 torr. The resulting films were characterized using scanning electron microscope (SEM), energy dispersive x-ray analysis (EDX) and atomic force microscopy (AFM). Lower pressures and deposition times resulted in thinner and more porous Pt films, while higher pressures and larger jet-substrate distances yielded isolated Pt nanoparticles in the 2-4 nm range. The latter are currently being deposited with an additional Ni-based precursor (bis-cyclopentadienyl Ni - Ni(Cp)2) to form PtNi alloy nanoparticles to investigate the potential use of alloying to make more efficient use of Pt. Electrochemical testing of nanoparticle catalysts for ORR activity are underway.