The effect of molten carbonates (MCs) on polarization resistance (RP), a direct measure of oxygen reduction reaction (ORR) activity, of a composite La0.8Sr0.2MnO3+δ/Ce0.8Gd0.2O2-δ (LSM/GDC) solid oxide fuel cell (SOFC) cathode has been systematically investigated in this study over a temperature range of 550–650°C and partial pressure of oxygen (pO2) span of 10−3 ∼ 1 atm. It is shown that the LSM/GDC cathode, either in the pristine or MC-modified states, can be generally modeled by two consecutive parallel circuits consisting of a resistance and a constant phase element (CPE). The high-frequency RP(HF)//CPE(HF) component is related to a charge-transfer process, while the low-frequency RP(LF)//CPE(LF) counterpart is associated with a surface oxygen dissociative adsorption process. Incorporation of an adequate amount of MC significantly reduces RP(LF) by as much as a factor of 10. Studies on the dependence of RP on temperature and pO2 further reveal that the rate-limiting step of a LSM/GDC cathode has shifted from the original surface oxygen dissociative adsorption to the formation of an intermediate CO2 −4 species in the presence of MC.
Published in Journal of The Electrochemical Societye, Volume 161, Issue 3, 2013, pages F226-F232.
©Journal of The Electrochemical Society 2013, The Electrochemcial Society.
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Publisher’s Version: http://dx.doi.org/10.1149/2.034403jes
Gong, Y., Li, X., Zhang, L., Tharp, W., Qin, C., & Huang, K. (December 20, 2013). Promoting Electrocatalytic Activity of a Composite SOFC Cathode La0.8Sr0.2MnO3+δ/Ce0.8Gd0.2O2-δ with Molten Carbonates. Journal of The Electrochemical Society, 161 (3), F226 – F232. http://dx.doi.org/10.1149/2.034403jes