Semester

Fall

Date of Graduation

2012

Document Type

Thesis

Degree Type

MS

College

Statler College of Engineering and Mineral Resources

Department

Mechanical and Aerospace Engineering

Committee Chair

Edward M Sabolsky

Abstract

LSCF [(La0.6Sr0.4)0.98 (Co0.2 Fe0.8) O3-delta], a solid oxide fuel cell (SOFC) cathode material was fabricated and foamed through a polymeric in situ foaming process to build an optimum porous architecture. The changes in the porous cathode microstructure with changes in the in situ foaming parameters were qualitatively investigated through back-scattered scanning electron microscope (SEM) imaging. Later, a quantitative analysis of the pore size, shape, area and distribution was completed on the same samples through a computational image analysis program called Image J (National Institute of Health, NIH). Electrochemical testing of the foamed cathode under different processing conditions including the baseline (un-foamed) cathode was performed through electrochemical impedance spectroscopy (EIS) of cathode symmetrical electrolyte-supported cells.;The porous cathode architecture formed through in situ foaming with 70% solids loading and a polymer precursor composition of 8:4:1 volume ratio (isocyanate: PEG: surfactant) within an terpineol/cellulose printing vehicle yielded the optimum microstructure displaying a substantial decrease in the electrode polarization resistance. It displayed a broad pore size distribution, higher mean pore area and more elongated pore channels with ∼40% and ∼50% less polarization than the baseline cell at 750°C and 800°C, respectively. These measurements were completed at open circuit voltage (OCV), 100 mA and 300 mA loading. Electrochemical Impedance Spectroscopy (EIS) testing for this cathode displayed ∼0.08 O cm2 -- polarization at 800°C (at OCV) and ∼50% increase in maximum power density with the foamed cathode over the baseline. Further improvements in the foamed cathode performance were obtained through the nano-catalyst incorporation into this microstructure. Platinum (Pt) nano-catalyst was impregnated into the microstructure using water based precursor (H2PtCl6.6H2O) solution; the interconnected porosity permitted the efficient infiltration of the solution throughout the bulk of the microstructure using a lower number of processing steps than the baseline (unfoamed) microstructure (per infiltration cycle). Also, a homogeneous dispersion of the nano-catalyst across the foamed cathode led to higher power densities, which is further reported in this study.

Download

Share

COinS