Analysis of Oxygen Dissolution Rate from Gas Phase into Nafion Surface and Development of an Agglomerate Model

Kudo, Kenji; Suzuki, Tomomichi; Morimoto, Yu

doi:10.1149/1.3484642

Cited by 98 publications

(84 citation statements)

References 15 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Therefore, high mass activity is necessary to decrease the Pt loading. However, electrochemical characterization of single cells 17 – 19 has revealed that high mass activity alone is not sufficient. For example, the characterizations by Greszler et al 19 demonstrated that decreased Pt loading is accompanied by an anomalous voltage drop owing to oxygen transport resistance in the cathode CL.…”

Section: Introductionmentioning

confidence: 99%

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells

et al. 2021

Self Cite

View full text Add to dashboard Cite

In recent years, considerable research and development efforts are devoted to improving the performance of polymer electrolyte fuel cells. However, the power density and catalytic activities of these energy conversion devices are still far from being satisfactory for large-scale operation. Here we report performance enhancement via incorporation, in the cathode catalyst layers, of a ring-structured backbone matrix into ionomers. Electrochemical characterizations of single cells and microelectrodes reveal that high power density is obtained using an ionomer with high oxygen solubility. The high solubility allows oxygen to permeate the ionomer/catalyst interface and react with protons and electrons on the catalyst surfaces. Furthermore, characterizations of single cells and single-crystal surfaces reveal that the oxygen reduction reaction activity is enhanced owing to the mitigation of catalyst poisoning by sulfonate anion groups. Molecular dynamics simulations indicate that both the high permeation and poisoning mitigation are due to the suppression of densely layered folding of polymer backbones near the catalyst surfaces by the incorporated ring-structured matrix. These experimental and theoretical observations demonstrate that ionomer’s tailored molecular design promotes local oxygen transport and catalytic reactions.

show abstract

Section: Introductionmentioning

confidence: 99%

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells

et al. 2021

Self Cite

View full text Add to dashboard Cite

show abstract

“…In recent years, Morimoto et al have shown high resistivity of O 2 permeation through the ionomer layer, in particular at the catalyst/ionomer interface [29][30][31][32]. While the impact at high current densities is thought to be a major factor inhibiting further reductions in PGM content [3], these results show that even at OCP, O 2 permeability resistance is most likely a factor in the initial Nernst potential loss.…”

Section: Ex Situ Gde Measurementsmentioning

confidence: 96%

An Examination of the Catalyst Layer Contribution to the Disparity between the Nernst Potential and Open Circuit Potential in Proton Exchange Membrane Fuel Cells

2021

View full text Add to dashboard Cite

The dependency of the Nernst potential in an operating proton exchange membrane fuel cell (PEMFC) on the temperature, inlet pressure and relative humidity (RH) is examined, highlighting the synergistic dependence of measured open circuit potential (OCP) on all three parameters. An alternative model of the Nernst equation is derived to more appropriately represent the PEMFC system where reactant concentration is instead considered as the activity. Ex situ gas diffusion electrode (GDE) measurements are used to examine the dependency of temperature, electrolyte concentration, catalyst surface area and composition on the measured OCP in the absence of H2 crossover. This is supported by single-cell OCP measurements, wherein RH was also investigated. This contribution provides clarity on the parameters that affect the practically measured OCP as well as highlighting further studies into the effects of catalyst particle surrounding environment on OCP as a promising way of improving PEMFC performance in the low current density regime.

show abstract

“…9,10,55 Since this overpotential occurs at high geometric current densities and low cathode rf values, i.e., at high local oxygen flux to the Pt surface, we hypothesize that it is related to oxygen transport limitations at the catalyst/ionomer interface. Suggestions for the observed voltage losses at high Pt-specific currents by other research groups include a limited dissolution of oxygen into the ionomer phase, 57 an intrinsically high transport resistance of the thin ionomer phase, 58 a limited effective ionomer surface, 10,37 or a decrease of the ORR kinetics at low potential. 59 Although we cannot exclude any one of these effects, a Pt/ionomer specific resistance appears most reasonable to explain the observed voltage losses at high Pt-specific currents, as the voltage profile shows a shape resembling a mass transport limitation, rather than a kinetic phenomenon.…”

Section: Ecsa Evolution During Voltage Cycling Asts-a Decrease Ofmentioning

confidence: 99%

Cathode Loading Impact on Voltage Cycling Induced PEMFC Degradation: A Voltage Loss Analysis

Harzer

Schwämmlein

Damjanović

et al. 2018

J. Electrochem. Soc.

138

172

View full text Add to dashboard Cite

This study focuses on voltage cycling induced degradation of cathodes with different loading (0.4 and 0.1 mg Pt /cm 2) when applying square wave or triangular wave based accelerated stress tests (ASTs) between 0.6 and 1.0 V RHE. The degradation of the H 2 /O 2 and H 2 /air performance upon extended voltage cycling (up to 30000 cycles) was analyzed in terms of the voltage loss contributions from ORR kinetics, O 2 mass transport resistances and proton conduction resistances in the cathode. The extent of cathode thinning due to carbon support corrosion was determined by post mortem electrode thickness measurements. Square waves were found to cause a more rapid loss of ECSA and mass activity compared to triangular waves, which was shown to be due to the longer hold periods at high potentials rather than to the rate of the potential transient. The observed increase of the O 2 mass transport resistance with voltage cycling was found to mainly depend on the available Pt surface area, while mass transport resistances due to carbon corrosion were found to be insignificant. Finally, it was shown that by lowering the upper potential limit to 0.85 V RHE , low-loaded catalyst layers can sustain 30000 potential cycles without degradation of the H 2 /air performance.

show abstract

Analysis of Oxygen Dissolution Rate from Gas Phase into Nafion Surface and Development of an Agglomerate Model

Cited by 98 publications

References 15 publications

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells

The role of oxygen-permeable ionomer for polymer electrolyte fuel cells

An Examination of the Catalyst Layer Contribution to the Disparity between the Nernst Potential and Open Circuit Potential in Proton Exchange Membrane Fuel Cells

Cathode Loading Impact on Voltage Cycling Induced PEMFC Degradation: A Voltage Loss Analysis

Contact Info

Product

Resources

About