PEFC Cathode Research Articles

Electrocatalytic Activity and Stability of M-Fe Catalysts Synthesized by Polymer Complex Method for PEFC Cathode

The polymerized complex (PC) method was used to synthesize highly dispersed iron-based catalysts for the oxygen reduction reaction (ORR). The catalysts were prepared with an addition of 1,10-phenanthroline (Phen) and transition metals (M), such as Ta, Ti, and W, in an attempt to enhance the ORR activity and durability of the catalysts. The composition and properties of the catalysts were characterized by thermogravimetric analysis, X-ray diffraction, and X-ray photoelectron spectroscopy. The catalyst components, after extensive dissolution in a strong acid solution, were characterized by inductively coupled plasma mass spectroscopy and ultraviolet-visible spectroscopy. It was found that the Ti-Fe catalyst showed improved ORR performance, and the Ta-Fe catalyst showed enhanced stability towards ORR in acidic solution. The catalytic activity and stability for ORR was observed by adding Ti or Ta into the catalyst formulation, suggesting that the interaction between added hetero-ions (Ti and Ta) and ionic Fe active sites was beneficial for the ORR. A single-cell test with the synthesized catalyst in the cathode initially generated a high power density, but the low stability remains an issue to be solved.

Development and Electrochemical Characterization of Pt Supported on Titanium Nitride for PEFC Cathodes

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Nonprecious Metal Oxide Based Powder Using Group 4 and 5 Metals for PEFC Cathode

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Two-phase flow measurement system for polymer electrolyte fuel cells

In this paper, a sensory system capable of measuring two-phase flow of water at the PEFC output is introduced. It works based on collecting and evaporating the liquid water that exits the PEFC in a vessel that is heated to a temperature above that of the fuel cell temperature. By measuring the vessel dew point temperature and flow rate, the mass of water in liquid and vapor phases are calculated. To demonstrate the capabilities of this measurement system, it is placed at the output of a PEFC cathode during membrane conditioning. The effect of two-phase flow on cell voltage reveals two distinct modes of liquid water transport in the PEFC cathode during membrane conditioning.

Pressure–voltage oscillations as a diagnostic tool for PEFC cathodes

In this work, pressure-induced voltage oscillations are explored as a novel diagnostic tool for PEFC cathodes. In this method, a small signal oscillation is imposed on the cathode outlet pressure. As a response to this pressure perturbation, the fuel cell voltage exhibits oscillations with the same frequency. The amplitude ratio and phase difference between the voltage and pressure oscillations embody diagnostic information about the operating conditions and processes in the PEFC cathode.

Oxygen Reduction Reaction Mechanism of Pt/Pd/C Core-Shell Catalyst for PEFC Cathode by Using In Situ Electrochemical XAFS

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Heteroatomic Polymers as Precursors for Non-precious PEFC Cathode Catalysts: Polyaniline and Polypyrrole

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J0601-2-4 パッシブ形PEFCの空気極近傍の流れの可視化(燃料電池システムおよび熱・物質移動)

J0601-2-4 パッシブ形PEFCの空気極近傍の流れの可視化(燃料電池システムおよび熱・物質移動)

Transient Multi-Scale Modeling of PtxCoy Catalysts Degradation in PEFC Environments

In this paper we focus on the understanding of the PtxCoy catalysts degradation in PEFC environments. A multiscale atomistic/kinetic model is derived providing new mechanistic insights on the impact of clusters nanostructure and operating conditions on PtxCoy materials durability. On the basis of ab initio (AI) data, we identify favorable pathways of the ORR on PtxCoy clusters and of the competitive Pt-Co dissolution in acidic media. The derived AI-kinetics is coupled to a description of the atomic reorganisation at the cluster level as function of the cumulated Pt and Co mass losses. This interfacial model is coupled with a transport microscale model of charges and O2 through the PEFC cathode, and simulation sensitivity studies to operating conditions and initial compositions/morphologies are performed. Experiments on DLIMOCVD-elaborated model electrodes are carried out by using RDE and half-cells: degradation structural changes are characterized by using TEM, XRD and XPS complementing the modeling studies.

Analysis of Pt Catalyst Degradation of a PEFC Cathode by TEM Observation and Macro Model Simulation

Pt particle size distributions at various positions in a cathode catalyst layer were evaluated by transmission electron microscopy (TEM) observation before and after a potential cycling test and by simple 1D macro model simulation to describe the degradation phenomena. Both the results showed similar tendencies: at the position near the membrane, the number of Pt particles for all sizes decreased with time; in contrast, at the position near the gas diffusion layer (GDL), the number of large Pt particles increased. The validity of this model is not verified yet because the precision of parameters is not confirmed. This model, however, can be used as a tool for deeper understanding of Pt degradation.

Surface Oxide Film and its Influence on the Oxygen Reduction on Pd-Co and Pt-Co PEFC Cathodes

PtCo and PdCo alloy electrodes were investigated in a 0.5 M sulfuric acid solution by electrochemistry, ellipsometry, laser Raman scattering spectroscopy, XPS, and GD-OES. The corrosion resistibility of Pt-Co and Pd-Co alloys decreased with increase of Co addition. The increase of Co addition, however, enhanced the catalytic efficiency on the ORR. The alloy surfaces may be covered by CoOOH and Pt or Pd oxide 2-3nm thick. At the potential of 1.2V vs. Ag/ AgCl/ sat. KCl, the thickness of oxide film increased with the Co addition. The presence of the oxide film on the alloy electrodes increases the overvoltage for the ORR. The effect of the oxide thickness on the ORR was discussed.

Catalytic Activity for Oxygen Reduction Reaction of Zirconium Oxynitride as a Cathode of PEFC

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Investigation of Degradation Mechanism of Pt/C PEFC Cathodes by Using Model Electrode

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Development of PEFC Cathode Catalysts based on Metal-oxide Supports

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Degradation of Carbon Supports in PEFC Cathode Electrode Investigated by Electrochemical STM : Effects of Platinum and Oxygen on Enhanced Carbon Corrosion

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Dissolution of Platinum-based PEFC Cathode Electrocatalysts

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Analysis of Pt Catalyst Degradation of a PEFC Cathode by TEM Observation and Micro Model Simulation

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Surface Oxide Film and its Influence on the Oxygen Reduction on Pd-Co and Pt-Co PEFC Cathodes

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Polypyrrole-Carbon Based Non-Precious Metal Nanocomposite Electrocatalysts for Oxygen Reduction Reaction at PEFC Cathode

not Available.

Effect of cathode binder IEC on kinetic and transport losses in all-SPEEK MEAs

The effect of ion exchange capacity (IEC) and loading of sulfonated polyether ether ketone (SPEEK) binder on PEFC cathode performance was studied. MEAs were prepared by decal transfer onto a SPEEK membrane (IEC-1.75 mequiv./g). The IEC of SPEEK binder in the MEA cathode was varied between 1.3 and 2.1 mequiv./g. Cathodes prepared with 30 wt.% SPEEK loading had an electrochemically active surface area (ECA) that was 25% lower than a Nafion ® bonded electrode with similar loading. Polarization curves were obtained at 80 °C and 75% RH with hydrogen as fuel and air and oxygen (O 2 ) as oxidants. Polarization data was analyzed to determine the relative contributions of different sources of polarization, namely membrane ohmic losses, electrode ohmic losses, and mass transport losses in the gas diffusion layer, binder film and electrodes. The electrode ohmic and mass transport losses decreased with increase in SPEEK IEC. However, even for the highest SPEEK IEC, these losses were higher than those obtained in a Nafion ® bonded electrode. This was attributed to the lower proton activity and O 2 permeability in SPEEK. The loading of SPEEK in the electrode was found to influence performance in the activation controlled region, with a loading of 7.5 wt.% giving the highest performance. However, gains in this region were negated at higher current densities due to enhanced ohmic and transport losses and MEAs with all binder loadings between 7.5 and 30 wt.% had similar limiting currents.