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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Li(RuO2)2 by Materials Project

LiRu2O4 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Li1+ is bonded in a 4-coordinate geometry to eight O2- atoms. There are a spread of Li–O bond distances ranging from 2.14–2.81 Å. There are two inequivalent Ru+3.50+ sites. In the first Ru+3.50+ site, Ru+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RuO6 octahedra. The corner-sharing octahedra tilt angles range from 45–57°. There are a spread of Ru–O bond distances ranging from 1.98–2.09 Å. In the second Ru+3.50+ site, Ru+3.50+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing RuO6 octahedra. The corner-sharing octahedra tilt angles range from 45–57°. There are a spread of Ru–O bond distances ranging from 1.95–2.08 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three Ru+3.50+ atoms. In the second O2- site, O2- is bonded to two equivalent Li1+ and three equivalent Ru+3.50+ atoms to form a mixture of distorted edge and corner-sharing OLi2Ru3 trigonal bipyramids. In the third O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent Li1+ and three Ru+3.50+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Li1+ and three equivalent Ru+3.50+ atoms to form a mixture of distorted edge and corner-sharing OLi2Ru3 trigonal bipyramids.

36 MATERIALS SCIENCE↗
NASA NTRS1990

Catalysts for ultrahigh current density oxygen cathodes for space fuel cell applications

The objective of this research was to identify promising electrocatalyst/support systems for the oxygen cathode in alkaline fuel cells operating at relatively high temperatures, O2 pressures and current densities. A number of materials were prepared, including Pb-Ru and Pb-Ir pyrochlores, RuO2 and Pt-doped RuO2, and lithiated NiO. Several of these were prepared using techniques that had not been previously used to prepare them. Particularly interesting is the use of the alkaline solution technique to prepare the Pt-doped Pb-Ru pyrochlore in high area form. Well-crystallized Pb(2)Ru(2)O(7-y) was used to fabricate high performance O2 cathodes with relatively good stability in room temperature KOH. This material was also found to be stable over a useful potential range at approximately 140 C in concentrated KOH. Other pyrochlores were found to be either unstable (amorphous samples) or the fabrication of the gas-fed electrodes could not be fully optimized during this project period. Future work may be directed at this problem. High area platinum supported on conductive metal oxide supports produced mixed results: small improvements in O2 reduction performance for Pb(2)Ru(2)O(7-y) but a large improvement for Li-doped NiO at room temperature. Nearly reversible behavior was observed for the O2/OH couple for Li-doped NiO at approximately 200 C.

Tryk, D.↗