Effects of carbon supports on Pt distribution, ionomer coverage and cathode performance for polymer electrolyte fuel cells

Park, Young-Chul; Tokiwa, Haruki; Kakinuma, Katsuyoshi; Watanabe, Masahiro; Uchida, Makoto

doi:10.1016/j.jpowsour.2016.02.091

Cited by 314 publications

(354 citation statements)

References 30 publications

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“…35 Table II depicts the results from the BET and the QSDFT analysis. The total surface area estimated by BET (first row in Table II) and QSDFT (i.e., the sum of micro and mesopore areas from QSDFT analysis) are in perfect agreement.…”

Section: Resultsmentioning

confidence: 99%

The Key to High Performance Low Pt Loaded Electrodes

Orfanidi

Madkikar

El‐Sayed

et al. 2017

J. Electrochem. Soc.

215

252

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The effect of ionomer distribution on the oxygen mass transport resistance, the proton resistivity of the cathode catalyst layer, and the H 2 /air fuel cell performance was investigated for catalysts with surface modified carbon supports. By introducing nitrogen containing surface groups, it was shown that the ionomer distribution in the cathodic electrode can be optimized to decrease mass transport related voltage losses at high current density. The in house prepared catalysts were fully characterized by TEM, TGA, elemental analysis, and XPS. Thin-film rotating disk electrode measurements showed that the carbon support modification did not affect the oxygen reduction activity of the catalysts, but exclusively affects the ionomer distribution in the electrode during electrode preparation. Limiting current measurements were used to determine the pressure independent oxygen transport resistance -primarily attributed to oxygen transport in the ionomer film -which decreases for catalysts with surface modified carbon support. Systematically lowering the ionomer to carbon ratio (I/C) from 0.65 to 0.25 revealed a maximum performance at I/C = 0.4, where an optimum between ionomer thickness and proton conductivity within the catalyst layer is obtained. From this work, it can be concluded that not only ionomer film thickness, but more importantly ionomer distribution is the key to high performance low Pt loaded electrodes.

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Section: Resultsmentioning

confidence: 99%

The Key to High Performance Low Pt Loaded Electrodes

Orfanidi

Madkikar

El‐Sayed

et al. 2017

J. Electrochem. Soc.

215

252

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“…19,56 Also, the carbon structures greatly affect the ionomer dispersion on the catalyst surface. 57,58 In an attempt to estimate IL coverage on the catalyst surface, we note that hydrogen adsorption behavior on low index Pt(hlk) facets differs dramatically in HClO 4 and H 2 SO 4 solutions, such as the Pt(100) and Pt(110). 6,17,59,60 With the aid of sensitivity of hydrogen adsorption region, we designed a method to study the IL coverage on the Pt.…”

Section: Resultsmentioning

confidence: 99%

Enhancing Pt/C Catalysts for the Oxygen Reduction Reaction with Protic Ionic Liquids: The Effect of Anion Structure

Huang¹,

Song

Morales‐Collazo

et al. 2017

J. Electrochem. Soc.

139

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Protic ionic liquids (ILs) have been recently studied as a potential approach to enhance oxygen reduction reaction (ORR) activity of carbon supported platinum catalysts (Pt/C) for application in polymer electrolyte membrane fuel cells. The high oxygen solubility in the ILs was suggested as one of the main reasons for the accelerated reaction rates. Because the nature of the anion of the IL has been associated with increased oxygen solubility, in this work we survey a number of ionic liquids with various anions to study this effect. While the search for direct correlation between the ORR activities and the oxygen solubilities does not produce any conclusive results, by contrast, the specific activity showed dependence on the availability of oxygenated species free Pt sites. This finding indicates that the inhibition of Pt oxidation and less adsorption of non-reactive species may also play an important role in the enhanced ORR activity. Moreover, the degree of IL coverage on the Pt surface was estimated using (bi)sulfate ions as an indicator. The surface coverage not only affected the ORR activity, but also the Pt dissolution process. This suggests that an optimal balance between activity and stability can be achieved on a partially covered Pt surface. The oxygen reduction reaction (ORR) that occurs on the cathode poses a major hurdle for the efficient utilization of polymer electrolyte fuel cells (PEMFC). Extensive studies have focused on developing novel catalysts to improve the efficiency of this reaction.1,2 The ORR involves multiple steps, among which O 2 + H + + e − ↔ OOH ads and OH ads + H + + e − ↔ H 2 O act as the potential rate determining steps. Simultaneously optimizing the Gibbs free energies for both steps to completely eliminate the overpotential is very challenging, and a ∼350 mV overpotenial is commonly observed, which is independent of the identity of the catalyst.3,4 The large overpotential has been generally attributed to the sluggish kinetics of the ORR and adsorption of oxygenated species (e.g. OH ad ) or other anions. 5 The coverage of the adsorbed oxygenated species (θ OH ad ) is unfavorable for the reaction, and the availability of the free metal surface (as expressed by the (1-θ OH ad ) term) is one of the governing factors for the ORR activity.6,7 As a result, much effort has been dedicated to weakening the bonding of OH to the catalyst surface either by shifting the d-band center of Pt 8,9 or by lateral repulsion from the supports (e.g. metal oxides). 10,11Anion adsorption on Pt also affects the ORR activity, and it is agreed that the occupation of active sites deactivates the sites and reduces the activity.12 In real-world membrane-electrode assembly (MEA), the Nafion membrane and ionomer, constituted by a Teflon-like backbone and an anionic cluster of sulfonic groups, 13 are widely employed as indispensable components. The interface between the Nafion and the metal has received great attention due to the strong irreversible sulfonate anions adsorption on the Pt. 12,[14][15][16] The de...

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“…106 The interior surface area in carbon support particles is less favourable due to their inferior character in terms of mass transport for the electrode reactions. 107 A novel combination of mercury porosimetry with computerized X-ray tomography was suggested by Malik et al…”

Section: Carbon Blackmentioning

confidence: 99%

A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells

et al. 2017

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A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: nanostructure, activity, mechanism and carbon support in PEM fuel cells. Journal of Materials Chemistry A, 5 (5). pp. 1808 -1825 . ISSN 2050 Access from the University of Nottingham repository: http://eprints.nottingham.ac.uk/40957/1/Journal%20of%20Materials%20Chemistry%20A %EF%BC%88C6TA08580F%20-%20corrected%20proofs%20-final%EF%BC%89.pdf Copyright and reuse:The Nottingham ePrints service makes this work by researchers of the University of Nottingham available open access under the following conditions. This article is made available under the University of Nottingham End User licence and may be reused according to the conditions of the licence. For more details see: http://eprints.nottingham.ac.uk/end_user_agreement.pdf A note on versions:The version presented here may differ from the published version or from the version of record. If you wish to cite this item you are advised to consult the publisher's version. Please see the repository url above for details on accessing the published version and note that access may require a subscription. Translation errors between word-processor files and typesetting systems can occur so the whole proof needs to be read. Please pay particular attention to: tabulated material; equations; numerical data; figures and graphics; and references. If you have not already indicated the corresponding author(s) please mark their name(s) with an asterisk. Please e-mail a list of corrections or the PDF with electronic notes attached -do not change the text within the PDF file or send a revised manuscript. Corrections at this stage should be minor and not involve extensive changes. All corrections must be sent at the same time.Please bear in mind that minor layout improvements, e.g. in line breaking, table widths and graphic placement, are routinely applied to the final version.We will publish articles on the web as soon as possible after receiving your corrections; n no late corrections will be made. The sluggish rate of the oxygen reduction reaction (ORR) in proton exchange membrane (PEM) fuel cells has been a major challenge. Significantly increasing efforts have been made worldwide towards a highly active ORR catalyst with high durability. Among all the catalysts exploited, Pt electrocatalysts are still the best in terms of a comprehensive evaluation. The investigation of Pt-based ORR catalysts is necessary for a practical ORR catalyst with low Pt content. This paper reviews recent progress in the studies of the mechanism, nanostructure, size effect and carbon supports of Pt electrocatalysts for the ORR. The importance of the size and structure control of Pt ORR catalysts, related with carbon support materials, is indicated. The potential methods for such control are discussed. The progress in theoretical studies and in situ catalyst characterization are also discussed. Finally, challenges and future developments are addressed.

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Effects of carbon supports on Pt distribution, ionomer coverage and cathode performance for polymer electrolyte fuel cells

Cited by 314 publications

References 30 publications

The Key to High Performance Low Pt Loaded Electrodes

The Key to High Performance Low Pt Loaded Electrodes

Enhancing Pt/C Catalysts for the Oxygen Reduction Reaction with Protic Ionic Liquids: The Effect of Anion Structure

A comprehensive review of Pt electrocatalysts for the oxygen reduction reaction: Nanostructure, activity, mechanism and carbon support in PEM fuel cells

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