Optimization of deposition parameters of thin films composed of Pt nanoparticles

The optimization of a number of film deposition variables was carried out for thin Pt films formed from a sol (generated by the reduction of hexachloroplatinic acid (CPA) by sodium ethoxide) containing Pt nanoparticles and a partially reduced Pt(II) species (NaPtCl 3(C 2H 4)). Increasing the film drying temperature leads to the thermal decomposition of this species, generating another Pt(II) crystalline species, as well as additional Pt. It also leads to improved inter-particle and particle–substrate contact of the 2 nm Pt nanoparticles, thereby increasing the Pt film charge density up to 200 °C drying temperature. Above this temperature, particle sintering occurs (8 nm diameter when dried to 400 °C), consistent with an observed loss in film charge. Increasing the withdrawal rate of the substrate from the sol leads to a thicker Pt film, while maintaining a constant Pt particle size. By changing the substrate from Au sputter-coated glass to carbon paper (CP), the Pt loading was increased; however, the effective usage of Pt was lower than anticipated, possibly related to the pooling of the liquid sol within the CP structure, resulting in poor nanoparticle dispersion.