Electrochemical Reduction of Oxygen and Nitric Oxide at Low Temperature on La1-xSrxCoO3-delta Cathodes

Six La1-xSrxCoO3-delta (x = 0, 0.05, 0.15, 0.25, 0.35, 0.50) perovskites were synthesized and characterized by powder X-ray diffraction and cyclic voltammetry on conical electrodes in either air or nitric oxide in argon at 200, 300, and 400 degrees C. At 200 degrees C, the current densities in air was the highest for the strontium-free cobaltite, whereas the current densities were the highest for La0.95Sr0.05CoO3-delta in the nitric oxide-containing atmosphere. This was also the compound with the highest I-NO/I-O2 current ratio at 200 degrees C. At higher temperatures, a limiting cathodic current was observed for all of the cobaltites, except for La0.50Sr0.50CoO3-delta, in both air and nitric oxide-containing atmosphere. This was attributed to a rate-limiting chemical step (i.e., dissociation of oxygen or nitric oxide) in the reaction sequence. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3464775] All rights reserved.