Semester

Spring

Date of Graduation

2020

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Yun Chen

Committee Member

Xueyan Song

Committee Member

Hailin Li

Abstract

The oxygen transport kinetics of the electrodes of Solid Oxide Fuel Cells (SOFC) are critical properties to achieve higher efficiencies in the cell. (La0.60Sr0.40)0.95Co0.20Fe0.80O3-x (LSCF) is a mixed ion-electron conductor material that is expected to be optimized and utilized as the cathode of the SOFC’s. The reason for LSCF to be considered as the next cathode material for SOFC is due to its high ionic and electronic conductivities, and high oxygen transport kinetics. Additionally, to the excellent properties that this material offers, it has been seen that the kinetic properties of the material can be further optimized by adding a metal oxide coating on top of the LSCF surface. In this research study, baseline LSCF pellets were fabricated using commercial powders, and their conductance was measured using the Electrical Conductivity Relaxation (ECR) technique. The surface exchange coefficient (k) and bulk diffusion coefficient (D) were determined by fitting the normalized conductance data into Fick’s second law. To further enhance the oxygen transport kinetics of the LSCF, surface modification was added on top of the baseline LSCF pellets using two methods: Atomic Layer Deposition (ALD) and ink coating. The materials that were used as surface modifiers were: CoOx, a mixture consisting CoOx and Pt, MnOx, and Pr2Ox. The oxygen transport kinetics of the surface-modified pellets were determined using the same method that was used for the baseline LSCF pellets. A comparison between the baseline and the surface-modified LSCF was presented along with the experimental errors. It was observed that surface modifiers can either enhance or reduce the oxygen transport kinetics of the perovskite oxide, depending on the type of coating that is added. All the coatings that were used in this project are metal oxides that have high electrical conductivity and ionic conductivity to transport the oxygen ions. Among the used coatings, the most remarkable one was CoOx that showed an enhancement of the surface exchange of LSCF while producing a minimal reduction of the diffusion coefficient. The addition of Pt on top of CoOx coating showed a surface exchange enhancement while maintaining the same diffusion coefficient as the perovskite oxide. Lastly, MnOx and Pr2Ox showed a reduction in the surface exchange and diffusion coefficient of the LSCF due to their lower electrical conductivities.

Embargo Reason

Patent Pending

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