Effect of Co doping on the electrochemical properties of Sr 2Fe1.5Mo0.5O6 electrode for solid oxide fuel cell

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Author(s)

  • Xin Pan
  • Beibei He
  • Shaorong Wang
  • Xiaojun Wu
  • Changrong Xia

Detail(s)

Original languageEnglish
Pages (from-to)4108-4115
Journal / PublicationInternational Journal of Hydrogen Energy
Volume38
Issue number10
Publication statusPublished - 1 Apr 2013
Externally publishedYes

Abstract

Co is doped to Sr2Fe1.5Mo0.5O6 to enhance its electrochemical activity as the cathode for intermediate- temperature solid oxide fuel cells. Pure cubic perovskites of Sr 2Fe1.5-xCoxMo0.5O6 (SF1.5-xCxM, x = 0, 0.5, 1) are synthesized using a glycine-nitrate combustion progress. The average thermal expansion coefficient varies from 15.8 to 19.8 × 10-6 K-1. The electrical conductivity increases while its activation energy decreases with increasing Co content. X-ray photoelectron spectroscopy analysis demonstrates mixed valences of Fe, Co and Mo, suggesting small polaron hopping mechanism. Electrical conductivity relaxation (ECR) measurement shows that the surface exchange coefficient increases about two orders of magnitude when the content increases from x = 0 to x = 1.0, i.e. from 2.55 × 10-5 to 2.20 × 10-3 cm s-1 at 750 °C. ECR also exhibits that chemical diffusion coefficient increases with Co content. Density Functional Theory calculation demonstrates that oxygen vacancy formation energy decreases with Co content, suggesting high oxygen vacancy concentration at high Co content. Impedance spectroscopy on symmetric cells consisting of SF1.5-xC xM electrodes and La0.8Sr0.2Ga 0.8Mg0.2O3-δ electrolytes shows that Co doping is very effective in reducing the interfacial polarization resistance, from 0.105 Ω cm2 to 0.056 Ω cm2 at 750 °C. These results suggest that Co doping into Sr2Fe1.5Mo 0.5O6 can substantially improve its electrochemical performance. © 2013, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Research Area(s)

  • Cathode, Co doping, Double perovskite, Solid oxide fuel cell, Sr2Fe 1.5Mo0.5O6

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