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 (NaPtCl₃(C₂H₄)). 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.