Thickness dependence of oxygen reduction reaction kinetics on strontium-substituted lanthanum manganese perovskite thin-film microelectrodes

Abstract

Oxygen reduction reaction (ORR) kinetics was investigated on dense La0.8 Sr0.2 Mn O3 microelectrodes as a function of temperature and microelectrode thickness using electrochemical impedance spectroscopy. The surface oxygen exchange and mixed bulk/three-phase-boundary (TPB) charge transfer process were found to control ORR kinetics at high and low temperatures, respectively. The transition temperature from the mixed bulk/TPB charge transfer control to surface oxygen exchange was found to be highly dependent on the microelectrode thickness (∼600°C for 65 nm vs ∼800°C for 705 nm). These findings can be used to guide the design of electrodes that can operate at intermediate temperatures. © 2009 The Electrochemical Society.