Date of Award

Summer 8-4-2023

Degree Type

Thesis

Degree Name

Doctor of Philosophy (PhD)

Department

Materials Science

Committee Chair

John D. Kirtley

First Advisor

Richard LaDouceur,

Second Advisor

Mario Caccia

Third Advisor

Julie E. Muretta

Fourth Advisor

Robert A. Walker

Abstract

A cermet anode comprising of yttria-doped barium zirconate, BZY and nickel, Ni is now the preferred choice of materials for use in proton conducting fuel cell (PCFC) anodes because of their influence on anode oxidation kinetics. The Ni grains, being in a solid solution with the BZY support, helps improve on the catalytic activity and conductivity, in addition to the relative stability of BZY in steam and hydrocarbon reforming environments, as well as BZY’s excellent protonic conductivity.

Ni-BZY based anodes, sintered onto a ~600-micron electrolyte-supported substrates of BZY, BCZY (yttria- and ceria-doped barium zirconate), and a BZY/BCZY dual electrolyte-layer substrate, complete with a BCZY-LSCF (lanthanum strontium cobalt ferrite) composite cathode are fabricated using facile approaches and tested in this study.

The study further investigated the electrochemical performances of the various single-layer cells, contrasted with their dual-layer counterpart under various fuel streams of pure hydrogen, neat and reformed-methane, and syngas. The bilayer cell attained a 34.1 % and 57.7 % more maximum power than the BZY and BCZY single-layer cells respectively at 700 when operated on syngas, with similar trends at 600 , and on different fuels. It was discovered in this study that coking is not only peculiar to Ni sites, but the BZY anode supports as well. Observations from operando FTIRES of the anode headspace and post-mortem characterization of the pristine and tested cells using Raman spectroscopy, X-ray diffraction, and SEM/EDX provided insights into causes of performance degradation to be from phase transformations, agglomeration, and coking; with the cells’ durability being dependent on the type of electrolyte material and architecture used.

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