Preparation of Pt-Ru alloyed thin films using a single-source CVD precursor

Treatment of (dimethylaminomethyl)ruthenocene with cis-Pt(DMSO) ₂Cl₂ led to the formation of a ruthenocenyl platinum complex [CpRu(η⁵-C₅H₃CH₂NMe ₂)Pt(DMSO)Cl] (1); subsequent treatment of 1 with [Na(hfac)] afforded an air-stable Pt-Ru complex [CpRu(η⁵-C₅H ₃CH₂NMe₂)Pt(hfac)] (2). Its volatility and other physical data relevant to CVD experiments were assessed by thermogravimetric analysis (TGA). The Pt-Ru thin films were then deposited at two deposition temperatures, 300°C and 400°C, using O₂ as the reactive carrier gas. The as-deposited thin films were characterized using energy dispersive X-ray (EDX), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and X-ray diffraction (XRD). Results indicated the formation of a homogeneous Pt-Ru solid solution at the lower deposition temperature. However, upon raising the temperature to 400°C, phase separation between Pt and Ru occurred, which then induced the growth of RuO₂ grains at the substrate surface and caused depletion of the alloy in ruthenium. The electrocatalytic activities of the films, in respect of methanol oxidation, were investigated, in half-cell experiments, by cyclic voltammetry.