A multiscale model for the oxide ion conducting and proton conducting solid oxide cells

Ma, Linjian

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https://hdl.handle.net/2142/101111 Copy

Description

Title

A multiscale model for the oxide ion conducting and proton conducting solid oxide cells

Author(s)

Ma, Linjian

Issue Date

2018-01-25

Director of Research (if dissertation) or Advisor (if thesis)

Aluru, Narayana R.

Department of Study

Mechanical Sci & Engineering

Discipline

Mechanical Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

multiscale modeling, continuum modeling, transition state theory, density functional theory, solid oxide cells

Abstract

Solid oxide cells (SOCs) are high-efficiency energy conversion devices under high temperature. However, the key reaction mechanisms governing the overall performance of SOCs are not well understood. Here, we develop a multiscale model combining density functional theory calculations, transition state theory and continuum modeling to elucidate the essential reaction steps and predict the performance of the device. Density functional theory calculations are used to obtain the free energy barriers for different reaction steps, transition state theory is used to predict the reaction rate constants for each step based on the free energy barriers, and the continuum theory utilizes the reaction rate constants to obtain the voltage loss-current density relations. We apply the methodology to both the oxide ion-conducting SOCs as well as the proton-conducting SOCs. The proposed multiscale model yields quantitative agreement with the voltage loss-current density data from experiments. The results indicate that as to the oxygen electrode reactions in the Lanthanum Strontium Cobalt Ferrite (La_{1-x}Sr_{x}Co_{1-y}Fe_{y} O_{3-\delta} or LSCF) based oxide ion-conducting SOCs, the reaction step involving the splitting of the surface oxygen molecules into oxide ions under SOFC mode and the combination of surface oxide ions into oxygen molecules under SOEC mode is the rate limiting reaction step, and the diffusion of oxide ions in bulk LSCF is the rate limiting diffusion step. As to the Pt/Y-doped BaZrO_3/Ag based proton-conducting SOFC, the cathode reactions are rate-limiting steps.

Graduation Semester

2018-05

Type of Resource

text

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http://hdl.handle.net/2142/101111

Copyright and License Information

Copyright 2018 Linjian Ma

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