Effect of annealing temperature on mixed proton transport and charge transfer-controlled oxygen reduction in gas diffusion electrode

Pyun

Israel Journal of Chemistry

et al. 2008

Self Cite

This article is concerned with the fundamental and experimental overview of the rotating disc electrode (RDE) and rotating ring–disc electrode (RRDE) techniques. First, this review provides a brief discourse on the basic concepts and general descriptions of the RDE and RRDE techniques. Then, the theoretical derivation of the governing equations for the RDE and RRDE is described with the definition of the important kinetic parameters. Finally, the experimental applications of RDE and RRDE techniques to investigate the mechanism and kinetics of oxygen reduction at Pt‐dispersed carbon (Pt/C) electrodes for fuel cells are discussed in detail from a practical point of view.

Section: Applications Of Rde and Rrde Techniques To Fuel Cell Analmentioning

confidence: 99%

Fundamentals of Rotating Disc and Ring–Disc Electrode Techniques and their Applications to Study of the Oxygen Reduction Mechanism at Pt/C Electrode for Fuel Cells

Pyun

Israel Journal of Chemistry

et al. 2008

Self Cite

“…18 The 45°slope is typical of homogenous ion transport through the CL, whereas other values may result from non-homogeneous transport properties, which is more likely to occur with thick electrodes and/or at high current density. 13 Strictly speaking, the classical Randles EEC corresponds to a thinfilm electrode representation, 19,20 which does not account for its actual volumetric character (Figure 1b). In this regard, agglomerate models provide a more appropriate description by considering charge and mass transport through the electrode volume.…”

mentioning

confidence: 99%

Transmission Line Impedance Models Considering Oxygen Transport Limitations in Polymer Electrolyte Membrane Fuel Cells

Touhami¹,

Mainka²,

Dillet³

et al. 2019

J. Electrochem. Soc.

Electrochemical Impedance Spectroscopy (EIS) is a well-established technique for studying Polymer Exchange Membrane Fuel Cells (PEMFC) but data interpretation remains delicate, mostly because impedance models are either based on oversimplified equations or conversely, include too many correlated parameters. It is thus crucial to carefully choose the models to interpret impedance data, according to FC materials and operation conditions. Most of PEMFC impedance spectra are composed of two loops in Nyquist plot that can be perfectly represented by classical Randles Electrical Equivalent Circuit (EEC). However, several spectra show a straight line at high frequencies associated with proton conduction in the cathode catalyst layer. Assuming an interface electrode, the Randles EEC is poorly adapted to such spectra and one will rather use Transmission Line Models (TLM). However, since TLM do not usually consider mass transport, it is necessary to adapt the EEC, especially at the cathode. Such EEC can then be used as general FC models independently of the occurrence of the straight line at high frequencies, i.e. independently of the ratio between proton conduction and reaction kinetics limitations. These TLM EECs are then used to analyze the layer(s) at the origin of oxygen transport limitations: catalyst and/or the gas diffusion layer.

Israel Journal of Chemistry

“…The theoretical treatment for the PCT by an analytical calculation allows us to extract quantitative estimates of kinetic parameters for the electrochemical reactions at porous electrodes. In addition, the analyses from the PCTs can substantiate the validity of the results of ac‐impedance spectra with respect to the oxygen reduction mechanism 17–22 .…”

Section: Introductionmentioning

confidence: 75%

“…The PCT technique has proven to be a reliable and powerful tool for the investigation of the reaction mechanism at porous cathodic electrodes in fuel cells 17–22 . One of the major advantages of the PCT technique is that the theoretical treatment involved is simpler and easier than that for the cathodic potentiodynamic polarisation method, since the current‐time relation in the PCT can be successfully obtained from the inverse Laplace transform of the electrode impedance or the analytical approach based upon the rate‐determining steps.…”

Section: Theoretical Analyses Of Potentiostatic Current Transient mentioning

confidence: 99%

Theoretical and Experimental Approaches to Oxygen Reduction at Porous Composite Electrodes for Fuel Cells by Analyses of ac‐Impedance Spectra and Potentiostatic Current Transients

Kim

Pyun

2008

Self Cite

This article covers the theoretical and experimental approaches to oxygen reduction at the porous composite electrodes for fuel cells by analyses of ac‐impedance spectra and potentiostatic current transient (PCT). First, the analysis methods based upon the thin‐film agglomerate model and the random packing model were introduced to theoretically calculate the ac‐impedance spectra. From the results, it is suggested that the capacitance dispersion in the high frequency range is closely associated with oxygen ion migration through the electrode. The deconvolution method by discrete Fourier transform and the PCT analysis method by inverse Laplace transform were also employed to simulate the distribution function of relaxation time and the PCTs, respectively. Finally, as an example of application, in the present work, we investigated the oxygen reduction mechanism at the porous (La0.85Sr0.15)0.9MnO3 (LSM)‐yittria‐stabilized zirconia (YSZ) composite electrodes as a function of sintering temperature by means of the analysis methods proposed above. From the dependences of the constant phase element exponent β for ion migration and the time to reach the steady‐state current tst on the sintering temperature, the capacitance dispersion in the high frequency range was discussed in terms of the distribution of the relaxation times for ion migration, which was greatly affected by the YSZ grain size.