Modeling SOFC Performance Incorporating Particle Morphologies and Partial Conductivity

Modeling SOFC Performance
Incorporating Particle Morphologies and Partial Conductivity

2015
AIChE Annual Meeting

Andrew
J. L. Reszka,Ryan C. Snyderand Michael Gross

One
of the biggest problems the world is facing today is finding a source of clean,
renewable energy.  It is estimated that
our current primary source of energy, crude oil reserves, will be depleted
within 40-50 years; and in the meantime through using crude oil we are
releasing harmful greenhouse gases into our atmosphere.  One very promising option to replace the
burning of crude oil is fuel cells.  In
this research we investigate Solid Oxide Fuel Cells (SOFCs). SOFCs are
electrochemical devices characterized by their solid, ceramic electrolytes that
directly oxidize a fuel to produce electricity with low emissions and high
efficiency. For the fuel cell to be functional the electrodes must have
porosity for fuel transport through the cell, oxygen ion conductivity to
transport the oxidizing agent to the fuel, electrical conductivity to transport
electrons from the reaction, and three phase boundary (TPB) sites to enable
chemical reaction.  Recent work has shown
that electrode fabrication by infiltration of electronic conductor/oxidation
catalyst particles into an oxygen ion rich porous backbone provides excellent
performance while decreasing the amount of conductor material necessary as
compared with other fabrication methods. Infiltrated electrodes also allow for
flexibility in composition and structure of the electrodes. This fabrication
method, however, has many design parameters whose impact on the resulting
cell's performance is not fully understood. Experimentally exploring these parameters
is very time consuming, thus a modeling effort can help to guide the desired
experiments.

In
this work, we show the development and results of a model for the design of a
SOFC electrode including its corresponding electrical conductivity, ceramic conductivity,
pore conductivity and TPB density for the formulated electrodes.  The model is based on the underlying physics
of the electrode fabrication process.  The fabrication process begins with the slurry
formation and film creation, followed by pore former combustion, ceramic
particle sintering and conducting particle infiltration.  Results of the model include the effect of
formulation parameters such as ceramic particle size, ceramic particle
morphology, electrical conductivity in the backbone, etc. on cell performance
characteristics such as three phase boundary density and electrical
conductivity.