Epilogue

Appleby, David J.

doi:10.7228/manchester/9780719075612.003.0007

Cited by 2 publications

(3 citation statements)

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“…At the cathode, the oxygen reduction reaction (ORR) proceeds on a Pt electrocatalyst supported on carbon in a porous gas diffusion electrode. Although the kinetics and mechanism of the ORR have been investigated with a variety of electrocatalyst materials and electrolytes (1)(2)(3)(4)(5)(6), the Pt or Pt-alloy have been the best electrocatalyst up to now. However, the ORR on Pt electrocatalyst is very irreversible, and the mass transport of reactive species dominates the ORR at high current density.…”

Section: Introductionmentioning

confidence: 99%

Effect of High Oxygen Permeable Ionomers on MEA Performance for PEFC

2013

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Asahi Glass Co., Ltd. (AGC) has been developing the perfluorinated ion exchange polymers (ionomers) in order to improve the performance, durability and robustness of MEA for PEFC. In the present report, the effect of the high oxygen permeable ionomers on MEA performance is described. The oxygen permeability of new ionomers was determined by means of potential step chronoamperometry (PSCA) using a Pt microelectrode. It was confirmed that the new ionomers had higher oxygen permeability compared with standard ionomer, and the permeability strongly depended on the ionomer density. And, the MEA performance was improved by using the high oxygen permeable ionomers for MEA cathodes. These results suggested that the high oxygen permeable ionomer was available for the reduction of Pt loading in MEA cathodes.

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Section: Introductionmentioning

confidence: 99%

Effect of High Oxygen Permeable Ionomers on MEA Performance for PEFC

2013

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“…To foster the widespread commercialization of polymer electrolyte fuel cells (PEFCs), a great research effort is currently dedicated to reduce the cost of the latter devices by decreasing Pt catalyst loadings in the membrane electrode assemblies (MEAs) and by suppressing the voltage losses during the long-term operation through enhanced catalyst stability. 1,2 In recent years, the catalyst's activity for the more Pt-demanding oxygen reduction reaction (ORR) has been drastically improved by alloying Pt with Co, Fe, or Ni [3][4][5] and by controlling the catalyst shape and crystal facets; 6,7 therefore, the latest ORR-catalysts exhibit more than 20 times higher surface-specific ORR-activity (SA) than conventional Pt nanoparticles supported on carbon (Pt/C) when electrochemically tested in liquid electrolyte half cell tests. 8 Furthermore, to prevent the voltage losses caused by carbon corrosion 9,10 upon high potential conditions (up to 1.5 V) encountered during fuel cell start-up/shut-down, graphitized-carbon supports 11 (e.g.…”

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confidence: 99%

“…Thus, to improve O 2 diffusivity in CLs from unsupported catalysts, it is necessary to design both catalyst shapeand pore-structures, as well as to understand the underlying structure formation mechanism during catalyst layer preparation. 25 In this respect, we have recently reported on the O 2 -diffusion issues discussed above upon testing an unsupported Pt 3 Ni alloy aerogel catalyst consisting of a 3D nanochain network in a differential fuel cell. 26 Initially, the Pt 3 Ni aerogel MEA displayed a high current density performance significantly poorer than that of Pt/C under H 2 /air operation.…”

mentioning

confidence: 99%

Tomographic Analysis and Modeling of Polymer Electrolyte Fuel Cell Unsupported Catalyst Layers

Ishikawa¹,

Henning²,

Herranz³

et al. 2018

J. Electrochem. Soc.

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Polymer electrolyte fuel cells' (PEFCs) widespread commercialization is hindered by the devices' limited durability, in terms caused by the corrosion of the carbon support used in the Pt-based PEFC catalysts. Using unsupported electrocatalysts could mitigate such durability issues, but little is known regarding the manner in which their processing into catalyst layers (CLs) affects pore size distribution (PSD) and PEFC performance. Thus, we have used a computational model to investigate the modes of agglomerate packing in CLs made from unsupported Pt 3 Ni nanochain ensembles (aerogels) or Pt black, and complemented this analysis with focused ion beam scanning electron microscopy tomography of corresponding real CLs. 3D structures, PSDs and tortuosities were obtained for real and computed CLs and were found to be in good agreement. The Pt black CL mainly exhibits large and straight pores (>100 nm wide), while the Pt 3 Ni aerogel CL mostly features small and twisted pores (< 100 nm wide) that cause the significantly poorer O 2 mass transport (vs. Pt black) observed in PEFC experiments. Moreover, this modeling approach leads to key insights on the working principle of a filler material used for positively shifting the average PSD and improving the PEFC performance of the Pt 3 Ni CL.

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Epilogue

Cited by 2 publications

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Effect of High Oxygen Permeable Ionomers on MEA Performance for PEFC

Effect of High Oxygen Permeable Ionomers on MEA Performance for PEFC

Tomographic Analysis and Modeling of Polymer Electrolyte Fuel Cell Unsupported Catalyst Layers

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