Highly conductive nano-sized Magnéli phases titanium oxide (TiO_x)

Despite the strong recent revival of Magnéli phase TiO_x as a promising conductive material, synthesis of Magnéli phase TiO_x nanoparticles has been a challenge because of the heavy sintering nature of TiO₂ at elevated temperatures. We have successfully synthesized chain-structured Magnéli phases TiO_x with diameters under 30 nm using a thermal-induced plasma process. The synthesized nanoparticles consisted of a mixture of several Magnéli phases. A post-synthesis heat-treatment was performed to reduce the electrical resistivity without changing the particle morphology. The resistivity of the heat-treated particle was as low as 0.04 Ω.cm, with a specific surface area of 52.9 m² g^-1. The effects of heat-treatment on changes in the crystal structure and their correlation with the electron conductivity are discussed based on transmission electron microscopy images, X-ray diffraction spectra, and X-ray adsorption fine structure spectra. Electrochemical characterization using cyclic voltammetry and potentiodynamic scan shows a remarkable electrochemical stability in a strongly oxidizing environment.