GEORGIA INSTITUTE OF TECHNOLOGY

Under the provisions of the regulations for the degree

DOCTOR OF PHILOSOPHY

on Friday, July 26, 2019

1:30 PM

in MoSE 3201A

will be held the

DISSERTATION DEFENSE

for

Ryan Joe Murphy

"A New Family of Proton Conducting Electrolytes with Enhanced Stability for Reversable Fuel Cell Operation: BaHf_xCe_0.8-xY_0.1Yb_0.1O₃"

Committee Members:

Prof. Meilin Liu, Advisor, MSE

Prof. Hamid Garmestani, MSE

Prof. Preet Singh, MSE

Prof. Mark Losego, MSE

Prof. Angus Wilkinson, Chemistry

Abstract:

Solid oxide fuel cell (SOFC) technology has the potential to be one of the most efficient energy conversion technologies and the same technology can be used to efficiently produce several chemical species such as hydrogen and syngas through reverse operation, known as solid oxide electrolysis cells (SOEC).  However, the long-term performance of these systems is often limited by degradation of the electrolyte.  In order to address the degradation issues, this work has developed a new family of proton conducing electrolyte materials, BaHf_xCe_0.8-xY_0.1Yb_0.1O₃ (BHCYYb), which demonstrates much improved stability while maintaining similar or higher conductivities than current state-of-the-art materials.  This resulted in SOFC performance which rivals that of the current best performance reported in literature, but with better durability.  In addition to its success as an electrolyte for hydrogen operation, BHCYYb has been shown to possess higher stability through long term chemical stability and long-term conductivity tests. To take advantage of the higher stability, long term tests of cells fabricated with BHCYYb were tested as reversible fuel cells as well as SOECs for CO₂-H₂O co-electrolysis.   Finally, the performance of BHCYYb was attempted to be further improved by studying novel dopants in the BaHfO₃ system.