Surface modification of SOFC cathodes by Co, Ni, and Pd oxides

By Paige, Julian M.; Cheng, Yuan; Pepin, Paul A.; Curran, Christopher D.; Sun, Danyi; Chen, Mavis U.; McIntosh, Steven; Vohs, John M.; Gorte, Raymond J.
Published in Solid State Ionics 2019

Abstract

The effect of adding transition-metal catalysts to the surfaces of Solid-Oxide-Fuel-Cell (SOFC) cathodes was examined. Monolayer amounts of Pd, Ni, and Co were deposited by atomic layer deposition (ALD) to cathodes prepared by impregnation of La0.8Sr0.2FeO3 (LSF), La0.8Sr0.2CoO3 (LSCo), and La0.6Sr0.4 Co0.2Fe0.8O3 (LSCF) into YSZ scaffolds. Incorporating the catalysts by ALD allowed modification of the surface composition without changing the cathode surface area or structure. X-ray Photoelectron Spectroscopy and High Sensitivity-Low Energy Ion Scattering were used to confirm ALD growth rates that were measured gravimetrically. Electrochemical impedance spectroscopy indicated that the addition of Pd had a small negative effect on all of the cathodes. Ni and Co exhibited only a small effect on LSCo and LSCF cathodes but both decreased the cathode impedance for LSF. It is suggested that an essential feature in cathode promotion by Co and Ni is that these cations are incorporated into the perovskite surface and thereby increase the concentration of oxygen vacancies, while Pd only blocked adsorption sites.

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