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Abstract: The electrode reaction of porous La0.6Sr0.4Co0.8Fe0.2O3−δ films deposited onto Ce0.9Gd0.1O1.95 (CGO) was investigated by impedance spectroscopy within the temperature and oxygen partial pressure (pO2) ranges of 500≤ T ≤700°C and 10−4

Abstract: The electrode reaction of the perovskite phases Sr1−x La x Co0.8Fe0.2O3−δ (x =0.1 and 0.6) on Ce0.9Gd0.1O1.95 has been investigated by impedance spectroscopy in the temperature range 600≤ T ≤800 °C. Thick porous electrodes (t ∼20 μm) were sprayed on Ce0.9Gd0.1O1.95 and ac impedance spectra were recorded on symmetrical cells at the equilibrium. The analysis of the complex impedance diagrams clearly indicates the presence of two contributions. The low frequency one was assigned to the gas phase oxygen diffusion through the porous electrode and a finite length diffusion (Warburg) impedance was used to describe the high frequency (HF) data. The polarization resistance of the HF impedance contribution (R w) is higher for x =0.1 while the activation energy of R w is higher for x =0.6. The variations of R w versus the La content, temperature and thickness indicate that the Warburg-type impedance contains information of both bulk oxygen diffusion and surface processes. [Copyright &y& Elsevier]

Abstract: Polarization modulated infrared reflection absorption spectroscopy (PM-IRRAS), which is one of the advanced FT-IR methods, was combined with conventional electrochemical techniques for in situ observation of high temperature electrode reactions at 773 K in oxygen partial pressure of 3×104 Pa. PM-IRRAS method can detect surface species selectively with high sensitivity at high temperatures without background measurement to cancel the infrared absorption by gas phase. Two different O2(g), Pt/YSZ electrochemical half cells were prepared as simple models of gas-electrodes. One of them had a working electrode which was composed of uniformly distributed platinum; the other had an island-networked platinum electrode. On the former electrode, PM-IRRAS detected a concentration change of adsorbed oxygen on Pt electrode with controlled cathodic overpotential. On the other hand, for the latter sample that showed smaller cathodic current, the signal of the adsorbed oxygen was suppressed by SiO2 impurity, whose spectrum was detected at 1220 cm− 1 by PM-IRRAS. It was shown that PM-IRRAS gives useful information on the state of adsorbed species which affect the electrode kinetics and the cell performance. [Copyright &y& Elsevier]

The hydrogen evolution (HER) from solid tetrabutylammonium hydroxide hydrate (C4H9)4NOH·30H2O (TBAOH30) has been studied at Au electrode in temperature range 220–305 K by electrochemical impedance spectroscopy (EIS).The shape of impedance spectra obtained at negative overpotentials depends on temperature. The best-fit equivalent circuit is composed of bulk resistance being in series with the constant phase element (CPE), representing impedance of electrode–electrolyte interface, parallel to charge transfer resistance. This indicates that the kinetics of the interfacial reaction is the rate-determining step. The linear Arrhenius type plot of the reciprocal of the charge transfer resistance was obtained at selected overpotentials. The value of the activation energy is equal 0.63 eV and it is larger than that of conduction process. The reasons of this difference is discussed. [Copyright &y& Elsevier]