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Aqua oxyhydroxycarbonate second phases at the surface of Ba/Sr-based proton conducting perovskites: a source of confusion in the understanding of proton conduction

Authors


Correspondence to: Ph. Colomban, Laboratoire de Dynamique, Interaction et Réactivité, UMR 7075 CNRS, Université Pierre et Marie Curie (UPMC), 4, Place Jussieu, 75005 Paris, France. E-mail address: philippe.colomban@upmc.fr

Abstract

Ba/Sr-based zirconates and cerates appear as potential proton conducting electrolytes for water electrolysers, hydrogen fuel cells and CO2/syngas converters. Such application requires long lifetime of each components: a good chemical and thermal stability of the device core and a low reactivity of the electrolyte membrane. It has been recently revealed that the complex infrared (IR) and Raman signatures observed for series of zirconates, cerates and/or titanates, assigned by some authors to the bulk protonic species actually arose from the surface species in the form of second undesirable phases: the high dense proton conducting ceramics being free from such signatures. In order to contribute to a better characterization of the phases that can be formed on the surface of proton conducting ceramics, we analysed the IR and Raman spectra of Ba/SrO, Ba/Sr(OH)2, Ba/SrCO3 in their dry and hydrated/deuterated forms in combination with thermogravimetric analysis. The results allowed us to confirm the above claim and to re-assign the vibrational spectra of perovskite materials wrongly attributed to the bulk protonic species. Since these second phases exhibit a high proton conductivity, their presence is very detrimental in the determination of intrinsic electrolyte bulk properties and interpretation of the conduction mechanisms. Copyright © 2012 John Wiley & Sons, Ltd.

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