Ruthenium Oxide sol-gels and carbon-supported ruthenium oxide composites for use in supercapacitors

Rowe, Aaron (2007) Ruthenium Oxide sol-gels and carbon-supported ruthenium oxide composites for use in supercapacitors. Masters thesis, Memorial University of Newfoundland.

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Abstract

The major goal of this research was to prepare and characterize highly capacitive materials containing ruthenium oxide for use in supercapacitors. This was achieved by fabricating high surface area materials in efforts to produce minimized mass loadings of ruthenium oxide with maximized electrochemical contributions to capacitance. -- Ruthenium oxide-titanium oxide hydrogels with a maximum specific capacitance of 10 F g⁻¹ were prepared via a sol-gel method. During voltammetric cycling, these gels experienced leaching of ruthenium into the electrolyte which slowly diminished their capacitive capabilities. Subsequent annealing partially resolved the leaching issue, but the hydrogel stability remained questionable. -- Carbon-supported ruthenium oxide composites were prepared using two types of high surface area carbon black as the supports onto which ruthenium nanoparticles were deposited via reduction of a ruthenium precursor. After deposition of the metal, ruthenium oxide was generated primarily by aging in air. Elemental analysis was used to elucidate the combined mass percent of ruthenium metal and/or oxide in the composites. X-ray photoelectron spectroscopy indicated that RuO₂ was the dominant oxide species and that unconverted ruthenium metal was present in the composites. X-ray diffraction confirmed this, with a mean ruthenium metal particle size of ca. 3.1 nm, while a mean ruthenium oxide particle size of 8.9 nm was found via transmission electron microscopy. The existence of ruthenium metal "cores" surrounded by ruthenium oxide "shells" was proposed to explain these results. Capacitance was measured via cyclic voltammetry. The highest specific capacitance of all the composites was 574 F g⁻¹. A maximum specific capacitance of 758 F g⁻¹ was found for ruthenium oxide itself amongst all composites.

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