Direct, Soft Chemical Route to Mesoporous Metallic Lead Ruthenium Pyrochlore and Investigation of its Electrochemical Properties

Abstract

Mesoporous, nanocrystalline metallic lead ruthenium oxide (a pyrochlore) was syntheSized through the formation of a mesostructured cohydroxide network via liquid crystal templating, and subsequent soft chemical oxidation that Crystallizes the oxide at low temperature. The stable S+I- interaction chemistry responsible for the templating methodology is elucidated. The formation of a disordered mesopotous structure with a pore volume of 0.18 cm(3)/g and walls comprised of nanocrystallites was confirmed by X-ray diffraction and conductivity, N-2 isotherm measurements, and TEM observations. The resistivity of mesopotous oxide at room temperature was 0:046 Omega.cm, only 2 orders of magnitude less than the single crystal; value, and one of the only two porous metallic oxides that are known to date. The electrocatalytic properties Of this material for oxygen reduction and evolution in aqueous and nonaqueous media were evaluated by cyclic vatarnmetry, chronoariaperometty, and linear sweep vdltarninetry. These techniques show that the synthesized pyttichlore lowers the overall oxidation voltage by 0.7 relative to carbon m nonaqueous, Li+ containing electrolyte. This is the result of its ability to both completely oxidize Li2O2 (at a relatively low potential) and electrocatalytically oxidize all known side products formed from electrolyte decomposition in the Li-O-2 battery. This further helps to explain the nature of "electrOcatalysis" in this system.