Modeling SOFC Performance Incorporating Particle Morphologies and Partial Conductivity
2015 AIChE Annual Meeting
Andrew J. L. Reszka, Ryan C. Snyder and 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.
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