Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells

Ott, Sebastian; Orfanidi, Alin; Schmies, Henrike; Anke, Björn; Nong, Hong Nhan; Hübner, Jessica; Gernert, Ulrich; Gliech, Manuel; Lerch, Martin; Strasser, Peter

doi:10.1038/s41563-019-0487-0

Cited by 441 publications

(448 citation statements)

References 33 publications

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“…While proton exchange membrane FCs (PEMFCs) are appealing, 12 their acidic environment is challenging. While platinum-based catalysts now reach high activity and durability, 13,14 catalysts free of Pt-groupmetals remain topical for cost and sustainability reasons. While metal-nitrogen-carbon (M-N-C) catalysts (M=Fe, Co) have demonstrated high ORR activity, [15][16][17][18] their durability in PEMFC is poor.…”

Section: Introductionmentioning

confidence: 99%

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Li¹,

Sougrati²,

Zitolo³

et al. 2020

Preprint

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While Fe-N-C materials are a promising alternative to platinum for catalyzing oxygen reduction in acidic polymer fuel cells, limited understanding of their operando degradation restricts rational approaches towards improved durability. Here we show that Fe-N-C catalysts initially comprising two distinct FeNx sites (S1 and S2) degrade via the transformation of S1 into iron oxides while the structure and number of S2 were unmodified. Structure-activity correlations drawn from end-of-test 57Fe Mössbauer spectroscopy reveal that both sites initially contribute to the ORR activity but only S2 significantly contributes after 50 h of operation. From in situ 57Fe Mössbauer spectroscopy in inert gas coupled to calculations of the Mössbauer signature of FeNx moieties in different electronic states, we identify S1 to be a high-spin FeN4C12 moiety and S2 a low- or intermediate spin FeN4C10 moiety. These insights lay the ground for rational approaches towards Fe-N-C cathodes with improved durability in acidic fuel cells.<br>

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Section: Introductionmentioning

confidence: 99%

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Li¹,

Sougrati²,

Zitolo³

et al. 2020

Preprint

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“…Among those FCs, the proton-exchange membrane FC (PEMFC) can be accounted, which are devices that convert the chemical energy contained in a fuel (namely methanol, hydrogen, among others) to electricity by using a hybrid polymer membrane that selectively allows the pass of protons from one electrode to the other, thus completing the catalytic conversion of hydrogen into water and electricity that can be used for vehicle movement. 2,3 An important feature of the PEMFC is the selective transportation of protons through its structure while keeping isolated the anodic and cathodic compartments 4 ; the transportation of protons is possible when there are polar species that can carry the transported charges while it has the mechanical strength to resist the pressure of the fuel. A polymer structure can accomplish those tasks by having a rigid backbone and polar pending groups such as sulfate or phosphate groups; thus, the glass transition is high enough for maintaining dimensional stability while transporting charges through its own structure.…”

Section: Introductionmentioning

confidence: 99%

Fabrication of hybrid proton‐exchange membranes using a brandnew high temperature ionic liquid as charge transporting and clay modifier

Arias

Bento

Marques

et al. 2020

J of Applied Polymer Sci

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The search for more compatibility between ionic liquids (ILs) and polymer matrices in proton-exchange membrane fuel cells (PEMFCs) is one of the ways in which IL leaking from proton-exchange membranes could be minimized. In this work, it is presented the synthesis of an aromatic high temperature ionic liquid (HTIL), which, incorporated into an aromatic matrix such as sulfonated polyether ether ketone (sPEEK), is expected to diminish the IL leaking that normally affects PEMFC. Phenylethylammonium trifluoromethane sulfonate (PhetaTfO) was successfully synthesized and characterized. Its melting point of 88 C makes it to classify as a HTIL and it was employed as modifier of natural Montmorillonite, forming the phenylethylammonium intercalated montmorillonite (MmtPheta) and thus, ternary membranes containing PhetaTfO, MmtPheta, and sPEEK were prepared and characterized. Immersion tests demonstrated a higher compatibility of PhetaTfO with matrix when compared to the reference DemaTfO, which was reflected in up to 30% lower IL loss by the synthesized IL than the DemaTfO; X-rays diffraction (XRD) patterns demonstrated that the modified clay was properly dispersed inside the membranes, while dynamic mechanical analyses (DMA) results indicated a strong plasticizer effect along the increase of PhetaTfO content inside the membrane, while at the same time, the conductivity increased in an exponential manner, which permitted to identify an empiric exponential equation to evaluate the effect of concentration on ionic conductivity. The maximum conductivity obtained at IL concentrations of around 38 wt% was 0.2 mS/cm. It could expect high ionic conductivities of 10 mS/cm when the concentration of this IL is 60%; nevertheless, in order to achieve that, crosslinking treatments should be done to give the membranes enough mechanical resistance.

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“…In this scheme, the balanced location of the metal nanoparticles just below the ionomer layers played a very important role. Direct contact with the ionomer would reduce the activity because of the poisoning of active surface sites by the ionomer sulphonate groups, as it occurs for catalyst nanoparticles located on exterior carbon surface [50,62]. On the other hand, catalyst nanoparticles deep inside the interior of the primary carbon pores remain inaccessible for the ionomer and, thus, suffer from proton and oxygen mass transport losses.…”

Section: Approaches To Improve Mass Transport In Low Pt-loaded Electrmentioning

confidence: 99%

Current challenges related to the deployment of shape-controlled Pt alloy oxygen reduction reaction nanocatalysts into low Pt-loaded cathode layers of proton exchange membrane fuel cells

Pan

Ott

Dionigi

et al. 2019

Current Opinion in Electrochemistry

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Ionomer distribution control in porous carbon-supported catalyst layers for high-power and low Pt-loaded proton exchange membrane fuel cells

Cited by 441 publications

References 33 publications

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Identification of Durable and Non-Durable FeNx Sites in Fe-N-C Materials for Proton Exchange Membrane Fuel Cells

Fabrication of hybrid proton‐exchange membranes using a brandnew high temperature ionic liquid as charge transporting and clay modifier

Current challenges related to the deployment of shape-controlled Pt alloy oxygen reduction reaction nanocatalysts into low Pt-loaded cathode layers of proton exchange membrane fuel cells

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