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Local Distortions and Dynamics in Hydrated Y-Doped BaZrO3

Abstract : Y-doped BaZrO3 is a promising proton conductor for intermediate temperature solid oxide fuel cells. In this work, a combination of static DFT calculations and DFT based molecular dynamics (DFT-MD) was used to study proton conduction in such a material. Geometry optimisations of 100 structures with a 12.5% dopant concentration allowed us to identify a clear correlation between the bending of the metal-oxygen-metal angle and the energies of the simulated cells. Depending on the type of bending, two configurations, designated as inwards bending and outwards bending, were defined. The results demonstrate that a larger bending decreases the energy and that the lowest energies are observed for structures combining inwards bending with 2 protons being close to the dopant atoms. These lowest energy structures are the ones with the strongest hydrogen bonds. DFT-MD simulations in cells with different yttrium distributions provide complementary microscopic information on proton diffusion as they capture the dynamic distortions of the lattice caused by thermal motion. A careful analysis of the proton jumps between different environments confirmed that the inwards and outwards bending states are relevant for the understanding of proton diffusion. Indeed, intra-octahedral jumps were shown to only occur starting from an outwards configuration while the inwards configuration seems to favor rotations around the oxygen. On average, in the DFT-MD simulations, the hydrogen bond lengths are shorter for the outwards configuration which facilitates the intra-octahedral jumps. Diffusion coefficients and activation energies were also determined and compared to previous theoretical and experimental data showing a good agreement with previous data corresponding to local proton motion.
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https://hal.archives-ouvertes.fr/hal-03033083
Contributor : Open Archive Toulouse Archive Ouverte (oatao) <>
Submitted on : Tuesday, December 1, 2020 - 11:01:00 AM
Last modification on : Monday, April 12, 2021 - 2:38:08 PM
Long-term archiving on: : Tuesday, March 2, 2021 - 6:46:12 PM

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Amangeldi Torayev, Luke Sperrin, Maria A. Gomez, John A. Kattirtzi, Céline Merlet, et al.. Local Distortions and Dynamics in Hydrated Y-Doped BaZrO3. Journal of Physical Chemistry C, American Chemical Society, 2020, 124 (30), pp.16689-16701. ⟨10.1021/acs.jpcc.0c04594⟩. ⟨hal-03033083⟩

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