Deconvolution of SOFC cathode polarization

FUEL 271

Eric D. Wachsman, ewach@mse.ufl.edu, Department of Materials Science and Engineering, University of Florida, Gainesville, FL 32611-6400
Fuel cells offer great promise as a clean and efficient process for directly converting chemical energy to electricity while providing significant environmental benefits. Among the different fuel cell technologies, solid oxide fuel cells (SOFCs) are unique in their ability to operate both within the current fossil fuel based energy infrastructure and as part of a future proposed hydrogen fuel infrastructure. Unfortunately, SOFC cost and reliability are limited by high operating temperature requirements. With the current state of the art SOFCs, performance at lower temperature is limited by cathode polarization.

In order to understand the various mechanistic contributions to cathode polarization and apply this knowledge to development of lower-polarization/lower-temperature SOFC cathodes, we have embarked on a multi-faceted, multi-disciplinary approach to deconvolute the various contributions to SOFC cathode polarization. This approach includes FIB/SEM to quantify the cathode microstructure (in terms of tortuosity and porosity for gas diffusion, solid-phase surface area for gas adsorption/surface diffusion, and triple phase boundaries for the charge transfer reaction) and heterogeneous catalysis techniques (temperature programmed desorption and reaction) to evaluate the O2 reduction mechanism at the gas-solid reaction interface. These results are then combined (and contrasted) with the more conventional electrochemical polarization techniques (impedance spectroscopy and I-V behavior) to try and elucidate each of the mechanisms as a function of material and microstructure. The progress to date on this investigation will be presented.