High surface proton conduction of a-axis oriented CeO_2−δ thin film on (200) YSZ substrate

Abstract

We have prepared a-axis oriented CeO2-δ thin films prepared on yttria-stabilized zirconia: YSZ single crystal substrates by RF magnetron sputtering using a ceramic target. The amount of oxygen vacancies was quantitatively evaluated by X-ray absorption spectroscopy and defect chemical analysis. In terms of its electronic structure, the O 1s photoemission spectrum of wet-annealed film shows an O-H bond peak, which suggests proton conduction. The thin film annealed at 600 °C in a wet atmosphere exhibit high proton conductivity of more than 101 Scm-1K at medium temperature range from 300 to 550 °C by thermal activation process and surface proton conductivity by Grotthuss mechanism below 50 °C. The enhancements of proton conductivities are due to large amount of oxygen vacancies of ~3.3% at the surface of wet-annealed thin film. These results indicate that the wet-annealed thin film can be applied as an electrolyte for electrochemical device operating below 50 °C.