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Title: Role of associated defects in oxygen ion conduction and surface exchange reaction for epitaxial samaria-doped ceria thin films as catalytic coatings

Samaria-doped ceria (SDC) thin films are particularly important for energy and electronic applications such as micro-solid oxide fuel cells, electrolysers, sensors and memristors. In this paper we report a comparative study investigating ionic conductivity and surface reactions for well-grown epitaxial SDC films varying the samaria doping concentration. With increasing doping above 20 mol% of samaria, an enhancement in the defect association was observed by Raman spectroscopy. The role of such defect associates on the films` oxygen ion transport and exchange was investigated by electrochemical impedance spectroscopy and electrochemical strain microscopy (ESM). The measurements reveal that the ionic transport has a sharp maximum in ionic conductivity and drop in its activation energy down to 0.6 eV for 20 mol% doping. Increasing the doping concentration further up to 40 mol%, raises the activation energy substantially by a factor of two. We ascribe the sluggish transport kinetics to the "bulk" ionic-near ordering in case of the heavily doped epitaxial films. Analysis of the ESM first order reversal curve measurements indicate that these associated defects may have a beneficial role by lowering the activation of the oxygen exchange "surface" reaction for heavily doped 40 mol% of samaria. We reveal in a model experiment throughmore » a solid solution series of samaria doped ceria epitaxial films that the occurrence of associate defects in the bulk affects the surface charging state of the films to increase the exchange rates. Lastly, the implication of these findings are the design of coatings with tuned oxygen surface exchange by control of bulk associate clusters for future electro-catalytic applications.« less
Authors:
 [1] ;  [2] ;  [2] ;  [3] ;  [1] ;  [4] ;  [1] ;  [3] ; ;  [1] ;  [3]
  1. Univ. of Roma, Rome (Italy)
  2. ETH Zurich, Zurich (Switzerland)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  4. Univ. of Salerno, Salerno (Italy)
Publication Date:
OSTI Identifier:
1261530
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
ACS Applied Materials and Interfaces
Additional Journal Information:
Journal Volume: 8; Journal Issue: 23; Journal ID: ISSN 1944-8244
Publisher:
American Chemical Society
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Center for Nanophase Materials Sciences (CNMS)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE defect associations; doped ceria; electrochemical strain microscopy; epitaxial thin films; Raman