Investigation of Redox Kinetics by Simultaneous In Situ Optical Absorption Relaxation and Electrode Impedance Measurements: Pr Doped Ceria Thin Films

摘要

Fast oxygen incorporation, essential for low temperature SOFCs, is enhanced in mixed ionic electronic conducting electrodes. In this study, simultaneous in situ measurement of transient optical absorption changes and electrode impedance is demonstrated as a powerful and convenient means for examining oxygen exchange kinetics in oxide thin films, utilizing Pr_(0.1)Ce_(0.9)O_(2-δ) as a model system. Absorption in the visible spectrum is tied to the fraction of Pr in its oxidized state (4+), which in turn is related to the material's oxygen deficiency. The origin of discrepancies between k_(chem) derived from optical relaxation measurements and k_(elec) from electrochemical measurements is discussed in terms of surface contamination and the potential catalytic effect of metal contacts.