Effect of Pressurization on Solid Oxide Cell Oxygen Electrodes: the Role of PrOx Nanoparticle Infiltration

Abstract

Pressurization of solid oxide cells improves performance by reducing electrode polarization resistance (R P ) and facilitates system integration with balance of plant components such as pressurized storage tanks. However, there are few reports on pressurization effects for electrodes designed for low-temperature operation and utilizing infiltrated catalysts. Here we report an electrochemical impedance spectroscopy study of high performing oxygen electrode materials, SrTi0.3Fe0.63Co0.07O3-∂ (STFC) and PrOx infiltrated STFC, for oxygen partial pressures () from 0.1 to 8 atm and temperatures from 550 to 650 °C. decreases more with pressurization for STFC:PrOx, fitting well to with an exponent n∼0.3, compared to n∼0.25 for STFC. The combination of PrOx infiltration and pressurization yields a substantial R P decrease, e.g., at 600 °C by ∼7 times from 0.36 Ω cm2 at = 0.2 atm for STFC to 0.055 Ω cm2 at = 4 atm for STFC:PrOx. A transmission-line-based circuit model impedance fit reveals that the significant oxygen surface reaction (Rsurf) resistance contribution decreases substantially with PrOx infiltration; and its dependence become more pronounced, with n increasing from ∼0.25 to ∼0.5. Rsurf for STFC:PrOx decreases so much at elevated that the electrode/electrolyte interface resistance dominates.