Measurement of Oxygen Exchange Kinetics on Thin-Film La_(0.6)Sr_(0.4)CoO_(3 - delta) Using Nonlinear Electrochemical Impedance Spectroscopy

摘要

In order to probe the mechanism of O_2 reduction on mixed-conducting oxides, we have measured the nonlinear harmonic impedance response of a dense thin-film electrode of La_(0.6)Sr_(0.4)CoO_(3 - delta). By combining a well-defined geometry with detection of small nonlinear harmonics, this approach reveals the nonlinear rate law governing O_2 reduction/oxidation. Comparison to various models based on nonequilibrium thermodynamics suggests that O_2 reduction on La_(0.6)Sr_(0.4)CoO_(3 - delta) is limited by dissociative adsorption. To the authors' knowledge, this is the first isolation of the full nonlinear rate law governing O_2 exchange on a perovskite oxide.