New Insight into the Properties of Proton Conducting Oxides from Neutron Total Scattering

TL;DR

This study uses neutron total scattering to reveal how local structural changes in cerate proton conductors influence their protonation and conduction, highlighting the role of oxygen vacancies and water uptake.

Contribution

It provides new insights into the local structural mechanisms underlying proton conduction in cerates through pair distribution function analysis.

Findings

Oxygen vacancy creation reduces local symmetry.

Water uptake restores local structure symmetry.

Ba-O shell flexibility is key to proton conduction.

Abstract

In this paper we investigated the most important family of proton conducting oxides, i.e. cerates, by means of pair distribution function analysis (PDF) obtained from total neutron scattering data. The results clearly demonstrates that the local structure plays a fundamental role in the protonation process. Oxygen vacancy creation by acceptor doping reduces the local structure symmetry which is then restored upon water uptake. This mechanism mainly involves the Ba-O shell which flexibility seems to be at the basis of the proton conduction mechanism, thus providing a direct insight on the design of optimal proton conducting materials.