Chemical Reactivity and Cathode Properties of LaCoO&lt;sub&gt;3&lt;/sub&gt; on Lanthanum Silicate Oxyapatite Electrolyte

Shunya Mihara,Takaya Akashi,Kiyoshi Kobayashi,Yoshio Sakka

doi:10.4028/www.scientific.net/kem.616.120

Chemical Reactivity and Cathode Properties of LaCoO<sub>3</sub> on Lanthanum Silicate Oxyapatite Electrolyte

Shunya Mihara, Takaya Akashi + Show 2 more

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https://doi.org/10.4028/www.scientific.net/kem.616.120

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Abstract

Chemical reactivity and cathode properties of LaCoO3 were investigated using new oxide ion conductor, lanthanum silicate oxyapatite. The LaCoO3 is found to be good candidate for cathode of the lanthanum silicate oxyapatite solid-electrolyte since no chemical reaction occurred between the LaCoO3 and lanthanum silicate oxyapatite heating at 1273 K for 60 h in air. Based on electrochemical measurements, lower overpotential between the LaCoO3 and lanthanum silicate oxyapatite was confirmed compared to the overpotential at YSZ/LaCoO3 interface. From analysis on the extended interfacial conductivity as function of oxygen activity at the triple phase boundary at fixed temperature, the overpotential evaluated by impedance spectra is the rate limiting process by oxygen diffusion on the LaCoO3 surface. Comparing to the bulk conductivity of LaCoO3, the electrode resistance evaluated by impedance spectra was confirmed to be different from the electrical transport properties of the LaCoO3 bulk.

Highlights

Lanthanum cobaltite with provskite structure (LaCoO3) is famous mixed conductor by electron holes and oxide ions and is the candidate for applications to cathode for solid oxide fuel cell (SOFC) and oxygen permeable membrane [1,2,3,4,5,6,7]
We focused on the LaCoO3 which could not apply as cathode material on the yttria stabilized zirconia (YSZ) electrolyte even though the LaCoO3 itself has excellent potential
From solid-state electrochemical measurements, high cathode performance was confirmed at the LaCoO3/lanthanum silicate oxyapatite interface by comparison to the interface at LaCoO3/YSZ

Summary

Introduction

Lanthanum cobaltite with provskite structure (LaCoO3) is famous mixed conductor by electron holes and oxide ions and is the candidate for applications to cathode for solid oxide fuel cell (SOFC) and oxygen permeable membrane [1,2,3,4,5,6,7]. The LaCoO3 shows high performance as SOFC cathode when yttria stabilized zirconia (YSZ) is used as solid electrolyte [1, 2], decrease in the cathode performance with continuous SOFC operation condition. It is necessary to replace the solid electrolyte from YSZ if one wants to utilize the excellent cathode property of LaCoO3 for SOFC. The lanthanum silicate oxyapatite shows high oxide ion conductivity even in the ceramic electrolyte. The lanthanum silicate oxyapatite is the candidate of the solid electrolyte material for middle temperature operation SOFC [15]. We focused on the LaCoO3 which could not apply as cathode material on the YSZ electrolyte even though the LaCoO3 itself has excellent potential. The chemical reactivity at the LaCoO3/lanthanum silicate oxyapatite interface and fundamental research on the cathode performance was investigated. Key Engineering Materials Vol 616 approach, we discussed about an origin of the overpotential between the LaCoO3/lanthanum silicate oxyapatite interface

Experimental

Results and discussion

Summary