Analysis of proton exchange membrane fuel cell catalyst layers for reduction of platinum loading at Nissan

Ohma, Atsushi; Mashio, Tetsuya; Sato, Kazuyuki; Iden, Hiroshi; Ono, Yoshiyuki; Sakai, Kei; Akizuki, Ken; Takaichi, Satoshi; Shinohara, Kazuhiko

doi:10.1016/j.electacta.2011.04.058

Cited by 192 publications

(189 citation statements)

References 24 publications

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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.

240

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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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.

240

191

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“…266,324 It was found that the resistance increased as Pt loading decreased. [132][133][134]264,266,325 The voltage-losses were found to scale with the Pt surface-area specific current density (as opposed to geometricarea specific current density) after correction for bulk (channels, DM, catalyst-layer length scale) transport losses by suitable models. 263 The local resistance is thus assumed to exist at or near the Pt surface to account for the unexplained higher voltage loss associated with lower Pt loading.…”

Section: Catalyst-layer Modelingmentioning

confidence: 99%

“…157,327 With the lower water contents (and perhaps the existence of different morphology and confinement driving the lower water uptake), it is not surprising that the ion conductivity is likewise depressed, [327][328][329] and is a function of ionomer content. 326,327,330,331 However, it should be noted that some studies suggest similar proton conductivity in catalyst layers as in bulk, 332,333 which may be due to measurement methods or perhaps anisotropic conductivity; more data is required. Finally, it is important to realize that understanding ionomer thin-film behavior is key not only for PEFC catalyst layers, but also for the characterization of bulk membrane surfaces, where the near-interface regions could be interpreted as thin-films.…”

Section: Catalyst-layer Modelingmentioning

confidence: 99%

“…Depending on catalyst-layer structure, two different modeling approaches have been employed that focus on low catalyst loadings: homogeneous model 134,[263][264][265] and agglomerate model, 132,133,266,267 both of which adapt the previous modeling methodologies (described in more detail below) to this situation. Most homogeneous models apply to an electrode with homogeneous properties and structure in which primary Pt/C catalyst particles are coated with an ionomer thin-film and the effectiveness of electrochemically active Pt surface is 100%.…”

Section: Catalyst-layer Modelingmentioning

confidence: 99%

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A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Weber

Borup

Darling³

et al. 2014

J. Electrochem. Soc.

498

394

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Polymer-electrolyte fuel cells are a promising energy-conversion technology. Over the last several decades significant progress has been made in increasing their performance and durability, of which continuum-level modeling of the transport processes has played an integral part. In this review, we examine the state-of-the-art modeling approaches, with a goal of elucidating the knowledge gaps and needs going forward in the field. In particular, the focus is on multiphase flow, especially in terms of understanding interactions at interfaces, and catalyst layers with a focus on the impacts of ionomer thin-films and multiscale phenomena. Overall, we highlight where there is consensus in terms of modeling approaches as well as opportunities for further improvement and clarification, including identification of several critical areas for future research. Fuel cells may become the energy-delivery devices of the 21 st century. Although there are many types of fuel cells, polymer-electrolyte fuel cells (PEFCs) are receiving the most attention for automotive and small stationary applications. In a PEFC, fuel and oxygen are combined electrochemically. If hydrogen is used as the fuel, it oxidizes at the anode releasing proton and electrons according toThe generated protons are transported across the membrane and the electrons across the external circuit. At the cathode catalyst layer, protons and electrons recombine with oxygen to generate waterAlthough the above electrode reactions are written in single step, multiple elementary reaction pathways are possible at each electrode. During the operation of a PEFC, many interrelated and complex phenomena occur. These processes include mass and heat transfer, electrochemical reactions, and ionic and electronic transport. * Electrochemical Society Active Member. z E-mail: azweber@lbl.govOver the last several decades significant progress has been made in increasing PEFC performance and durability. Such progress has been enabled by experiments and computation at multiple scales, with the bulk of the focus being on optimizing and discovering new materials for the membrane-electrode-assembly (MEA), composed of the proton-exchange membrane (PEM), catalyst layers, and diffusionmedia (DM) backing layers. In particular, continuum modeling has been invaluable in providing understanding and insight into processes and phenomena that cannot be resolved or uncoupled through experiments. While modeling of the transport and related phenomena has progressed greatly, there are still some critical areas that need attention. These areas include modeling the catalyst layer and multiphase phenomena in the PEFC porous media.While there have been various reviews over the years of PEFC modeling 1-7 and issues, [8][9][10][11][12][13][14] as well as numerous books and book chapters, there is a need to examine critically the field in terms of what has been done and what needs to be done. This review serves that purpose with a focus on transport modeling of PEFCs. This is not meant to be an exhaustive review...

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“…[1] Regrettably already for loadings below 0.10 mg Pt /cm² at the cathode side, the performance suffers quite drastically due to a poorly understood local resistance, which is thought to be related to an increased local mass-transport resistance (MTR), although other causes have been proposed as well. [2][3][4][5][6][7][8][9][10][11][12][13] In terms of physical interpretation, the MTR represents the local resistance of a reactant molecule towards reaching an active reaction site, which becomes more significant as the number of reaction sites decrease but the desired overall reaction rate remains the same.…”

Section: Introductionmentioning

confidence: 99%

Polarization loss correction derived from hydrogen local-resistance measurement in low Pt-loaded polymer-electrolyte fuel cells

Freiberg

Tucker

Weber

2017

Electrochemistry Communications

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The reduction of platinum-loading on the cathode side of polymer-electrolyte fuel cells leads to a poorly understood increase in mass-transport resistance (MTR) at high current densities.This local resistance was measured using a facile hydrogen-pump technique with dilute active gases for membrane-electrode assemblies with catalyst layers of varying platinum-loading (0.03-0.40 mg Pt /cm²). Furthermore, polarization curves in H 2 /air were measured and corrected for the overpotential caused by the increased MTR for low loadings on the air side due to the reduced concentration of reactant gas at the catalyst surface. The difference in performance after correction for all resistances including the MTR is minor, suggesting its origin to be diffusive in nature, and proving the meaningfulness of the facile hydrogen-pump technique for the characterization of the cathode catalyst layer under defined operation conditions.

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Analysis of proton exchange membrane fuel cell catalyst layers for reduction of platinum loading at Nissan

Cited by 192 publications

References 24 publications

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

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

A Critical Review of Modeling Transport Phenomena in Polymer-Electrolyte Fuel Cells

Polarization loss correction derived from hydrogen local-resistance measurement in low Pt-loaded polymer-electrolyte fuel cells

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