Platinum and platinum oxide nanoparticles generated by unipolar spark discharge

Platinum nanoparticles were generated by spark discharge in forming gas (95 vol% nitrogen and 5 vol% hydrogen) and in air. An in-house developed spark discharge generator was used featuring unipolar spark discharge characteristics. Platinum nanoparticles generated in forming gas are pure platinum, crystalline, and 2-10 nm in diameter. However, spark discharge in air produces complex, 10-50 nm, amorphous, non-stoichiometric platinum oxide particles containing nano-crystals of pure platinum about 5 nm in size on the surface. Independently of the carrier gas, the produced material also contains spherical fine particles of hundreds of nanometers in diameter, which are composed of platinum only. The amount of the spherical fine particles was quantified by X-ray diffraction, resulting in about 10% and 14% weight fraction, when generated in forming gas and in air, respectively.