Relationship between gas transport resistance in the catalyst layer and effective surface area of the catalyst

Iden, Hiroshi; Takaichi, Satoshi; Furuya, Yoshihisa; Mashio, Tetsuya; Ono, Yoshiyuki; Ohma, Atsushi

doi:10.1016/j.jelechem.2013.02.008

Cited by 34 publications

(45 citation statements)

References 29 publications

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“…A similar trend was reported in the literature for both aqueous electrochemistry [18,19] and solid-state electrochemistry utilizing a solid polymer electrolyte [14,20]. In our past work [10], it was verified that the loss of the HOR current in the high potential region is not caused by the suppression of the inherent Pt activity for HOR of individual sites but caused by site blocking. Therefore, the influence of the site blocking, which relates to effective surface area, eff S , might be obtainable by investigating the relation between mass transport, kinetic current, and potential.…”

Section: Change In Koutecky-levich Slopesupporting

confidence: 87%

“…This result suggested that the change in K-L slope is caused by the decrease in eff S , and k i for HOR is high enough regardless of the potential and coverage. The idea that k i did not matter to the current even at a high potential was explained in our past work [10] as well. However, the relation between eff S and the K-L slope needs to be clarified more for quantitative understanding.…”

Section: Change In Koutecky-levich Slopementioning

confidence: 83%

“…One of us has developed a method to evaluate the effective surface area, eff S , for the hydrogen oxidation reaction (HOR) as a function of potential by using the change of mass transport properties as a probe [10]. This method is applicable to a membrane electrode assembly which has a gas diffusion layer on its catalyst layer.…”

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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: Change In Koutecky-levich Slopesupporting

confidence: 87%

Section: Change In Koutecky-levich Slopementioning

confidence: 83%

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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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“…Redistribution subject to ECS terms of use (see 54.245.55.244 Downloaded on 2018-05-11 to IP A critical and unresolved challenge in PEMFCs that has arisen with the attempts at reducing Pt loading and cost is the lower than projected peak power for cathodes incorporating ultra-low Pt loadings. The issue is being studied intensively and different groups 114,[121][122][123][124][125] have identified several possible routes including catalyst interaction with Nafion. In MEAs of PEMFCs, since it is not possible to carry out an investigation in the absence of ionomer (ionomer is indispensable for proton conduction), the contribution of the ionomer adsorption/blocking cannot be easily examined.…”

Section: Discussionmentioning

confidence: 99%

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

Shinozaki

Zack

Pylypenko

et al. 2015

J. Electrochem. Soc.

234

191

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Platinum electrocatalysts supported on high surface area and Vulcan carbon blacks (Pt/HSC, Pt/V) were characterized in rotating disk electrode (RDE) setups for electrochemical area (ECA) and oxygen reduction reaction (ORR) area specific activity (SA) and mass specific activity (MA) at 0.9 V. Films fabricated using several ink formulations and film-drying techniques were characterized for a statistically significant number of independent samples. The highest quality Pt/HSC films exhibited MA 870 ± 91 mA/mg Pt and SA 864 ± 56 μA/cm 2 Pt while Pt/V had MA 706 ± 42 mA/mg Pt and SA 1120 ± 70 μA/cm 2 Pt when measured in 0.1 M HClO 4 , 20 mV/s, 100 kPa O 2 and 23 ± 2 • C. An enhancement factor of 2.8 in the measured SA was observable on eliminating Nafion ionomer and employing extremely thin, uniform films (∼4.5 μg/cm 2 Pt ) of Pt/HSC. The ECA for Pt/HSC (99 ± 7 m 2 /g Pt ) and Pt/V (65 ± 5 m 2 /g Pt ) were statistically invariant and insensitive to film uniformity/thickness/fabrication technique; accordingly, enhancements in MA are wholly attributable to increases in SA. Impedance measurements coupled with scanning electron microscopy were used to de-convolute the losses within the catalyst layer and ascribed to the catalyst layer resistance, oxygen diffusion, and sulfonate anion adsorption/blocking. The ramifications of these results for proton exchange membrane fuel cells have also been examined.

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“…Using the same experimental procedure, Owejan et al [26] further varied the Pt/C ratio and, and using a single-particle model, found that taking 5 into account interfacial resistances at both the gas/ionomer and ionomer/platinum interfaces yielded the best fit to the experimental data. Iden et al [27] proposed an alternative in-situ method based on gas crossover through the membrane to study hydrogen vs. oxygen transport resistances near the platinum surface. Also, ex-situ approaches using Nafion thin films cast on platinum electrodes have been demonstrated [28,29].…”

Section: Figure 1: Schematic Of Oxygen Diffusion Losses In a Fuel-celmentioning

confidence: 99%

Investigating fuel-cell transport limitations using hydrogen limiting current

Spingler

Phillips

Schuler

et al. 2017

International Journal of Hydrogen Energy

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Reducing mass-transport losses in polymer-electrolyte fuel cells (PEFCs) is essential to increase their power density and reduce overall stack cost. At the same time, cost also motivates the reduction in expensive precious-metal catalysts, which results in higher local transport losses in the catalyst layers. In this paper, we use a hydrogen-pump limitingcurrent setup to explore the gas-phase transport losses through PEFC catalyst layers and various gas-diffusion and microporous layers. It is shown that the effective diffusivity in the gas-diffusion layers is a strong function of liquid saturation. In addition, it is shown how the catalyst layer unexpectedly contributes significantly to the overall measured transport resistance. This is especially true at low catalyst loadings. It is also shown how the various losses can be separated into different mechanisms including diffusional processes and massdependent and independent ones, where the data suggests that a large part of the transport resistance in CLs cannot be attributed to a gas-phase diffusional process. The technique is promising for deconvoluting transport losses in PEFCs.2

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Relationship between gas transport resistance in the catalyst layer and effective surface area of the catalyst

Cited by 34 publications

References 29 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

Oxygen Reduction Reaction Measurements on Platinum Electrocatalysts Utilizing Rotating Disk Electrode Technique

Investigating fuel-cell transport limitations using hydrogen limiting current

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