CrO3 Based Proton Conductors

Published

November 1, 2016

Author(s)

Laura Mazzei, Max Wolff, Daniele Pergolesi, Joseph Dura, Lars Borjesson, Philipp Gutfreund, Marco Bettinelli, Thomas Lippert, Maths Karlsson

Abstract

Epitaxial thin films of the proton conducting perovskite BaZr_0.53In_0.47O_3-δH^d0.47-2δ, grown by pulsed laser deposition, were investigated in their hydrated and dehydrated conditions through a multi-technique approach with the aim to study the structure and proton concentration depth profile and their relationship to proton conductivity. The techniques used were X-ray diffraction, X-ray and neutron reflectivity, nuclear reaction analysis, and Rutherford backscattering, together with impedance spectroscopy. The obtained proton conductivity and activation energy are comparable to literature values for the bulk conductivity of similar materials, thus showing that grain-boundary conductivity is negligible due to the high crystallinity of the film. The results reveal an uneven proton concentration depth profile, with the presence of a 3-4 nm thick, proton-rich, layer with altered composition, likely characterised by cationic deficiency. While this surface layer either retains or re-obtains protons after desorption and cooling to room temperature, the bulk of the film absorbs and desorbs protons in the expected manner. It is suggested that the protons in the near-surface, proton-rich region are located in proton sites characterized by relatively strong O-H bonds due to weak hydrogen-bond interactions to neighboring oxygen atoms and that the mobility of protons in these sites generally lower than in proton sites associated with stronger hydrogen bonds. This not only suggests that strongly hydrogn-bonding configurations are preferable for high proton conduction, but, on a mechanistic level, also that the rate of proton conductivity is determined by hydrogen-bond mediated proton transfer between neighbouring oxygen atoms rather than the diffusional rotation of the -OH group between such transfers.

Citation

Journal of Physical Chemistry C

Volume

120

Issue

50

Pub Type

Journals

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Keywords

Neutron Reflectometry, Solid Oxide Fuel Cell, proton conductivity, surface segregation, epitaxial perovskite thin film, hydrogen

Citation

Mazzei, L. , Wolff, M. , Pergolesi, D. , Dura, J. , Borjesson, L. , Gutfreund, P. , Bettinelli, M. , Lippert, T. and Karlsson, M. (2016), CrO₃ Based Proton Conductors, Journal of Physical Chemistry C, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=921814 (Accessed October 14, 2024)