ChemInform Abstract: CATHODIC AND ANODIC POLARIZATION PHENOMENA AT PLATINUM ELECTRODES WITH DOPED CERIUM OXIDE AS ELECTROLYTE. I. STEADY‐STATE OVERPOTENTIAL

Wang, D. Y.; Nowick, A. S.

doi:10.1002/chin.197943024

Cited by 2 publications

(2 citation statements)

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“…As shown in Supplementary Fig. 12 and from our previous work43, the cathode reciprocal resistances at high and low frequencies show different oxygen partial pressure dependencies m (as shown in equation (5)): m is ∼0.25 at high frequencies (HF) and ∼0.5 at low frequencies (LF) According to the relationship between pO 2 dependencies and rate-determining-steps as discussed by other researchers495051, the polarization resistance at HF is likely related to charge transfer and that at LF to non-charge-transfer steps.…”

Section: Resultsmentioning

confidence: 70%

A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

et al. 2017

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The slow activity of cathode materials is one of the most significant barriers to realizing the operation of solid oxide fuel cells below 500 °C. Here we report a niobium and tantalum co-substituted perovskite SrCo0.8Nb0.1Ta0.1O3−δ as a cathode, which exhibits high electroactivity. This cathode has an area-specific polarization resistance as low as ∼0.16 and ∼0.68 Ω cm2 in a symmetrical cell and peak power densities of 1.2 and 0.7 W cm−2 in a Gd0.1Ce0.9O1.95-based anode-supported fuel cell at 500 and 450 °C, respectively. The high performance is attributed to an optimal balance of oxygen vacancies, ionic mobility and surface electron transfer as promoted by the synergistic effects of the niobium and tantalum. This work also points to an effective strategy in the design of cathodes for low-temperature solid oxide fuel cells.

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Section: Resultsmentioning

confidence: 70%

A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

et al. 2017

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“…Alternatively, one cannot rule out the possibility that the charge transfer reaction, in which adsorbed oxygen atoms on the Pt surface react with electrons and form oxygen ions on the electrolyte surface, is the rate‐limiting step. Such a mechanism was proposed much earlier from the study of the polarization phenomenon on Pt∣ceria, in particular, by Wang and Nowick 45,46 . In this case, a slope of −1/4 is expected at a low oxygen partial pressure in a log–log plot of vs po 2 , which gradually shifts to a value of +1/4 at a high oxygen partial pressure.…”

Section: Discussionmentioning

confidence: 72%

Impedance Spectroscopy as a Tool for Chemical and Electrochemical Analysis of Mixed Conductors: A Case Study of Ceria

Lai

Haile

2005

Journal of the American Ceramic Society

362

409

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The AC impedance response of mixed ionic and electronic conductors (MIECs) is derived from first principles and quantitatively compared with experimental data. While the approach is not entirely new, the derivation is provided in a unified and comprehensive manner. Using Sm 0.15 Ce 0.85 O 1:925Àd with Pt electrodes as a model system, a broad spectrum of electrical and thermodynamic properties is extracted solely from the measurement of impedance spectra over wide oxygen partial pressure and temperature ranges. Here, the oxygen partial pressure was varied from air [p O2 5 0.21 atm] to H 2 [p O2 5 10À31 atm], and the temperature was varied from 5001 to 6501C. It was essential for this analysis that the material under investigation exhibit, under some conditions, purely ionic behavior and, under others, mixed conducting behavior. The transition from ionic to mixed conducting behavior is recognizable not only from the oxygen partial pressure dependence of the total conductivity but also directly from the shape of the impedance spectra. Within the electrolytic regime, the impedance spectra (presented in Nyquist form) take the shape of simple, depressed arcs, whereas within the mixed conducting regime (under reducing conditions), the spectra exhibit the features associated with a half tear-drop-shaped element. Parameters derived from quantitative fitting of the impedance spectra include the concentration of free electron carriers, the mobilities and activation energies for both ion and electron transport, the electrolytic domain boundary, and the entropy and enthalpy of reduction. In addition, the electrochemical behavior of O 2 and H 2 at the Ptjceria interface has been characterized from these measurements. Under oxidizing conditions, the data suggest an oxygen electrochemical reaction that is rate limited by the dissociated adsorption/diffusion of oxygen species on the Pt electrode, similar to PtjYSZ (yttria-stabilized zirconia). Under reducing conditions, the inverse of the electrode resistivity obeys a p À1=4 O2 dependence, with an activation energy that is similar to that measured for the electronic conductivity. These results suggest that ceria is electrochemically active for hydrogen electro-oxidation and that the reaction is limited by the rate of removal of electrons from the ceria surface.

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ChemInform Abstract: CATHODIC AND ANODIC POLARIZATION PHENOMENA AT PLATINUM ELECTRODES WITH DOPED CERIUM OXIDE AS ELECTROLYTE. I. STEADY‐STATE OVERPOTENTIAL

Cited by 2 publications

References 1 publication

A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

A niobium and tantalum co-doped perovskite cathode for solid oxide fuel cells operating below 500 °C

Impedance Spectroscopy as a Tool for Chemical and Electrochemical Analysis of Mixed Conductors: A Case Study of Ceria

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