Defect Chemistry and Hydrogen Transport in La/Sr-Based Oxyhydrides

Rowberg, Andrew J. E.; Weston, Leigh; Van de Walle, Chris G.

doi:10.1021/acs.jpcc.0c09222

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Defect Chemistry and Hydrogen Transport in La/Sr-Based Oxyhydrides

Rowberg, Andrew J. E.·Weston, Leigh·Van de Walle, Chris G.

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Abstract

Oxyhydrides in the series La 2 – y Sr y LiH 1 + y O 3 – y are attractive materials for solid-state hydride electrolytes. However, their chemical stability is poor, and thus far only La 2 LiHO 3 (y = 0) has been demonstrated in a working fuel cell. Using a first-principles approach to study defect chemistry and stability, we find that La 2 LiHO 3 can be stabilized over a range of H-rich, O-poor chemical conditions, while Sr 2 LiH 3 O has low stability. Here, defects are critical for ionic transport and for stability, particularly in Sr 2 LiH 3 O, in which anion antisites and H vacancies readily form. In fact, we show that the ground-state structure of Sr 2 LiH 3 O is inherently disordered. La 2 LiHO 3 has low conductivity, which we connect to the high formation energy of defects such as VO and OH that are necessary for hydride conduction. When Sr 2 LiH 3 O is grown under carefully selected conditions, V H + defects can be made prevalent; these defects give rise to much higher ionic conductivity than can be obtained in La 2 LiHO 3 . In general, we show that the choice of synthesis conditions is vital when seeking to optimize the stability and ionic conductivity of these oxyhydrides, thereby tailoring them for use in solid-state hydrogen fuel cells.

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08 HYDROGEN Solid-state electrolytes anions chemical structure defects density functional theory energy hydride conductors native point defects oxyhydrides thermodynamic properties

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Rowberg, Andrew J. E., Weston, Leigh, Van de Walle, Chris G.. 2021-01-26. Defect Chemistry and Hydrogen Transport in La/Sr-Based Oxyhydrides. https://doi.org/10.1021/acs.jpcc.0c09222

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