An in situ technique for analyzing ionomer coverage in catalyst layers

Iden, Hiroshi; Ohma, Atsushi

doi:10.1016/j.jelechem.2013.01.026

Cited by 71 publications

(69 citation statements)

References 26 publications

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“…9, the plots only shifted vertically regardless of the parameters, and there was no change in the gradient. This change was similar to the case when a polymer film, such as Nafion ® film was formed onto a RDE [15,26]. There was no change in the K-L slope although, of l  = 0.5 : active domain : inactive domain course, the intercept shifted.…”

Section: Diffusion-only Approximationsupporting

confidence: 62%

“…The detail was explained in Ref. 15. Then, the roughness factor was evaluated from H Q , the geometrical area of the disk electrode and a charge to Pt surface area conversion factor of 210 C cm -2 Pt for a smooth polycrystalline Pt.…”

Section: Conditioning Of Pt Rde and Roughness Factor Measurementmentioning

confidence: 99%

“…It was reported that the size of the Pt particle affects Pt oxide formation notably [31]. As the size of the Pt particle in the MEA was very small (about 3 nm [15]), the growth of Pt oxide is known to be shifted to lower potential compared to polycrystalline platinum, hence this would give rise to a difference in  . The difference in electrolytes could have a large influence on  .…”

Section: mentioning

confidence: 99%

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Analysis of effective surface area for electrochemical reaction derived from mass transport property

Iden

Kucernak

2014

Journal of Electroanalytical Chemistry

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The effective surface area, eff S , for electrochemical reaction at a Pt electrode was analyzed using mass transport property as a probe. This parameter is different to the socalled electrochemical surface area (ECA), which is usually obtained from the amount of protons which are underpotentially deposited, UPD H , or by CO stripping. The analysis was done using both experimental and numerical methods. In experiments, a rotating disk electrode (RDE) was used under the conditions where the Pt surface can be partially covered by Pt oxides or CO. For numerical analysis, three mass transport models based on diffusion, convection and convective-diffusion were used. As a result, it was found that it is possible to estimate eff S from the change in Koutecky-Levich slope at high rotation speeds. The analysis suggests that eff S does decrease notably from relatively low potential (around 0.4 V), even though it is not obvious in measured currents as the effect is masked by the low rates of mass transport. The analysis also suggests that there is a large difference in eff S with different methods, namely, estimation from the amount of Pt oxides and the analysis derived from mass transport property.Keywords: Effective surface area; RDE; HOR; catalyst Research highlights ▶ Estimation of effective surface area was possible by analyzing mass transport. ▶ Inactive domain size could also be estimated from the analysis. ▶ Effectiveness decreased notably from relatively low potential unlike Pt oxide growth.

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Section: Diffusion-only Approximationsupporting

confidence: 62%

Section: Conditioning Of Pt Rde and Roughness Factor Measurementmentioning

confidence: 99%

Section: mentioning

confidence: 99%

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Analysis of effective surface area for electrochemical reaction derived from mass transport property

Iden

Kucernak

2014

Journal of Electroanalytical Chemistry

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“…Different analysis methods were used for detection of ionomer size in electrodes. 19,35,36 In catalytic layers of fuel cells an operation-induced thinning of the ionomer films that partly encapsulate the platinum covered carbon (Pt/C) agglomerates has been reported. 13,37,38 The observed stronger thinning of the ionomer layers in the anode at samples cut close to the hydrogen inlet and with the use of thin membranes was explained by the higher concentration of highly active hydrogen radicals.…”

Section: F3140mentioning

confidence: 99%

High-Resolution Analysis of Ionomer Loss in Catalytic Layers after Operation

Morawietz

Handl

Oldani

et al. 2018

J. Electrochem. Soc.

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The function of catalytic layers in fuel cells and electrolyzers depends on the properties of the ionically conductive phase, which are most commonly perfluorinated ionomers based on Nafion and Aquivion. An analysis by atomic force microscopy reveals that the ultrathin ionomer films around Pt/C agglomerates have a thickness distribution ranging from 3.5 nm to 20 nm. Their conductivity and gas permeation properties determine the fuel cell performance to a large extend. For electrodes in Aquivion-based membraneelectrode-assemblies operation-induced structure changes were investigated by means of material-and conductivity-sensitive atomic force microscopy, infrared spectroscopy and electron-dispersive X-ray analysis. The observed thinning of the ultrathin ionomer films was mainly caused by polymer degradation deduced from reduced swelling after long-time operation and a significant loss of ionomer with operation time detected by infrared spectroscopy. From the linear thickness increase of the ultrathin films with rising humidity, a mainly layered structure of the ionomer was deduced. An influence of thickness of such ultrathin ionomer films on fuel cell lifetime was found by analysis of differently prepared membrane-electrode-assemblies, where a linear increase of irreversible degradation rate with ionomer film thickness in the electrodes of unused membrane-electrode-assemblies was found.

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“…Adding Nafion to the catalyst layer, first the ionomer fills up the pores of the catalyst layer. While macropores can be filled completely, it is difficult to fill the micropores [8]. Further addition of ionomer results in a formation of films on the surface of the electrode (pores are reported to be completely filled in the range from 0.8 to 1.0 mg of Nafion/cm 2 of electrode).…”

Section: Introductionmentioning

confidence: 99%

The colloidal tool-box approach for fuel cell catalysts: Systematic study of perfluorosulfonate-ionomer impregnation and Pt loading

2016

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In this study the correlation between the impregnation of proton exchange membrane fuel cell catalysts with perfluorosulfonate-ionomer (PFSI) and its electrochemical and electrocatalytic properties is investigated for different Pt loadings and carbon supports using a rotating-disk electrode (RDE) setup. We concentrate on its influence on the electrochemical surface area (ECSA) and the oxygen reduction reaction (ORR) activity. For this purpose platinum (Pt) nanoparticles are prepared via a colloidal based preparation route and supported on three different carbon supports. Based on RDE experiments, we show that the ionomer has an influence both on the Pt utilization and the apparent kinetic current density of ORR. The experimental data reveal a strong interaction in the microstructure between the electrochemical properties and the surface properties of the carbon supports, metal loading and ionomer content. This study demonstrates that the colloidal synthesis approach offers interesting potential for systematic studies for the optimization of fuel cell catalysts.

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An in situ technique for analyzing ionomer coverage in catalyst layers

Cited by 71 publications

References 26 publications

Analysis of effective surface area for electrochemical reaction derived from mass transport property

Analysis of effective surface area for electrochemical reaction derived from mass transport property

High-Resolution Analysis of Ionomer Loss in Catalytic Layers after Operation

The colloidal tool-box approach for fuel cell catalysts: Systematic study of perfluorosulfonate-ionomer impregnation and Pt loading

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