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Pure H conduction in oxyhydrides

Science  18 Mar 2016:
Vol. 351, Issue 6279, pp. 1314-1317
DOI: 10.1126/science.aac9185

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Transporting the hydrogen anion

Hydrogen cation (H+) transport is common in both biological systems and engineered ones such as fuel cells. In contrast, the transport of hydrogen anions (H) is far less common and is usually coupled with or compromised by the parallel transport of electrons. Kobayashi et al. examined the transport of H in a series of rare-earth lithium oxyhydrides (see the Perspective by Yamaguchi). They prevented electronic conduction by using Li+ as a countercation. In an electrochemical cell, the oxyhydride material acted as a solid-state electrolyte for H, which suggests an alternative avenue for developing energy storage devices.

Science, this issue p. 1314; see also p. 1262

Abstract

A variety of proton (H+)–conducting oxides are known, including those used in electrochemical devices such as fuel cells. In contrast, pure H conduction, not mixed with electron conduction, has not been demonstrated for oxide-based materials. Considering that hydride ions have an ionic size appropriate for fast transport and also a strong reducing ability suitable for high-energy storage and conversion devices, we prepared a series of K2NiF4-type oxyhydrides, La2-x-ySrx+yLiH1-x+yO3-y, in the hope of observing such H conductors. The performance of an all-solid-state TiH2/o-La2LiHO3 (x = y = 0, o: orthorhombic)/Ti cell provided conclusive evidence of pure H conduction.

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