Event
Chemically Stable Proton Conducting Materials for Reversible Solid Oxide Fuel Cells
Thursday, September 28, 2017
1:00 p.m.-2:00 p.m.
UMERC Conference Room 1202 EGL
Catherine Stephens
301 405 9378
csteph5@umd.edu
Enrico Traversa
School of Energy Science and Engineering,
University of Electronic Science and Technology of China, Chengdu 611731, Sichuan, China
The high cost of solid oxide fuel cells (SOFCs), associated with their high operating
temperatures, hampers their broad use and causes long-term stability problems. A step
forward towards reducing the SOFC working temperature at 600°C or below can be the use of
high temperature proton conductor (HTPC) oxides as electrolytes, due to their lower
activation energy for proton conduction (0.3-0.6 eV), with respect to oxygen-ion conducting
electrolytes [1]. We have recently made significant progresses following various strategies [2] in the development of chemically-stable HTPC electrolytes by improving the sinterability of Y-doped barium zirconate (BZY) [3], which offers excellent chemical stability against CO 2
and H 2 O reaction and high bulk conductivity [4], but low conductivity values for sintered
pellets due to the presence of blocking grain boundaries. Co-doping BZY with Pr allowed
obtaining a chemically stable, sinterable electrolyte that showed a conductivity of 0.01 S/cm
at 600°C.
However, efficient cathodes need to be developed to avoid polarization losses at such a
low temperature [5]. We followed a rational approach to tailor the cathode materials with low
overpotential, considering that the materials should concurrently possess electron, proton and oxygen-ion conductivities, given the different species involved in the cathode reactions, and we succeeded in obtaining an area specific resistance as low as 0.157 Ω cm 2 at 600°C [6].
The development of these materials allowed us to start investigation on solid oxide
electrolysis cells (SOECs), where the use of HTPC electrolytes can alleviate the problems
encountered with oxygen-ion electrolytes, which are high working temperatures, dilution of
the produced H 2 , and fuel electrode oxidation [7]. We were recently able to report first on the SOEC test using BZY electrolytes [8]. Inthis presentation, the past work on protonic SOFCs will be briefly summarized, and then the recent work on SOECs and SOFCs will be presented. In addition, preliminary results of the recent efforts in scaling up both planar and microtubular cells and in improving the performance through the tailoring of the nanostructure of cathode materials will be shown.
