Durability of Unsupported Pt-Ni Aerogels in PEFC Cathodes

Henning, Sebastian; Herranz, Juan; Ishikawa, Hiroshi; Kim, Bae-Jung; Abbott, Daniel F.; Kühn, Laura; Eychmüller, Alexander; Schmidt, Thomas J.

doi:10.1149/2.0131712jes

Cited by 25 publications

(37 citation statements)

References 62 publications

(97 reference statements)

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“…These observations from the cross section image analysis further agree with the evolution of ECSAs throughout the AST in Figure 2B discussed above, whereby the ECSA loss of ≈75% experienced by Pt/CB reflects the drastic changes in its CL structure. Moreover, the behavior of Pt 3 Ni and Pt/CB under high potential excursions is comparable to our own findings in previous works, 10,11 whereby the Pt/CB degradation in separated potential regimes of 0.6-1.0 and 1.0-1.5 V RHE (somehow decoupling the effects observed in the 0-1.5 V RHE tests included herein) was related to Pt-nanoparticle growth and carbon support corrosion, respectively. 7,8,31,32,36 As in the EOL I/E curves in Figure 1, the deterioration of Pt/GCB (ECSA loss ≈50%) is worse than that of Pt 3 Ni aerogel, but less severe than for Pt/CB, highlighting the advantage of working with more corrosionstable carbon supports.…”

Section: Resultssupporting

confidence: 91%

“…Inspired by the latter approach, and motivated by our recent results with PEFC cathodes from unsupported Pt 3 Ni aerogel catalysts that demonstrate excellent stability during start-up/shut-down accelerated stress tests (ASTs), 10,11 this work investigates the applicability of the = These authors contributed equally to this work. * Electrochemical Society Student Member.…”

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confidence: 99%

“…9 Alternatively, material-based mitigation strategies include composite anode electrodes exhibiting high HOR and oxygen evolution reaction (OER) activity, as well as corrosion-resistant, non-carbon supported or even completely support-free catalysts. 9 Inspired by the latter approach, and motivated by our recent results with PEFC cathodes from unsupported Pt 3 Ni aerogel catalysts that demonstrate excellent stability during start-up/shut-down accelerated stress tests (ASTs), 10,11 this work investigates the applicability of the 3 Ni electrodes were prepared as described in reference 10 by mixing 5 mg of catalyst, 0.7 mg of K 2 CO 3 (99.995% trace metals basis, Sigma Aldrich), 18 mg of Na + -exchanged Nafion solution (prepared from a 1:2 volumetric mixture of 0.1 M NaOH and Nafion solution, 13 and equal to a Nafion-to-catalyst-ratio of 0.12) and 1.0 ml of an 8 wt% aqueous isopropanol solution (ultrapure water, 18.2 M cm, Elga Purelab Ultra and isopropanol, 99.9%, Chromasolv Plus for HPLC, Sigma Aldrich). After ultrasonication (USC100T, 45 kHz, VWR) for 30 minutes and spray coating (using a frame to confine the coating to an active area of 1 cm 2 ), the resulting catalyst coated membranes (CCMs) were immersed into 1 M H 2 SO 4 solution (96%, Suprapur, Merck) overnight (≈16 hours), followed by rinsing with ultrapure water and drying under ambient conditions.…”

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confidence: 99%

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Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

Henning

Shimizu

Herranz

et al. 2018

J. Electrochem. Soc.

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Mitigating catalyst corrosion is crucial for the commercial success of polymer electrolyte fuel cells (PEFCs). Novel catalysts that can withstand the harsh conditions in case of gross fuel (i.e. H 2 ) starvation events at the PEFC anode are needed to increase the fuel cell stack's service life and to meet the durability targets set for automotive applications. To make progress in this respect, we have tested an unsupported, bimetallic Pt 3 Ni alloy (aerogel) catalyst at the PEFC anode and subjected it to a stress test that mimics the high potentials (≥ 1.5 V vs. the reversible hydrogen electrode) encountered upon fuel starvation. In contrast to commercial carbon-supported platinum catalysts (Pt/C), the Pt 3 Ni aerogel displays excellent durability and performance retention in end-oflife fuel cell polarization curves. Additionally, the aerogel catalyst shows ≈35% higher surface-specific activity for the hydrogen oxidation/evolution reaction than Pt/C. These results highlight the great potential of using novel unsupported catalysts at the anode of PEFCs. Polymer electrolyte fuel cells (PEFCs) customarily rely on platinum nanoparticles supported on carbon (Pt/C) to catalyze the anodic hydrogen oxidation and the cathodic oxygen reduction reactions (HOR and ORR, respectively, leading to anode and cathode sometimes being referred to as hydrogen-and oxygen-electrodes).1,2 Among the latter, the ORR is catalytically more demanding, and thus higher Pt loadings are implemented in PEFC cathodes vs. anodes (up to ≈0.4 vs. ≈0.05 mg Pt /cm 2 geom ).3 Irrespectively of this activity difference, both anodic and cathodic Pt/C catalysts suffer from significant corrosion of the carbon support during the high potential excursions (> 1 V vs. the reversible hydrogen electrode, V RHE ) concomitant to PEFC operation, which limits the device's service life.4 Potentials ≥ 1.5 V RHE on the cathode side can for instance be caused by PEFC start-up/shut-down and local fuel starvation. 5,6 To minimize the damage of these start-up/shut-down events, technical solutions like a highflow air purge of the anode compartment that minimizes the residence time of the H 2 /air anode front have been developed. 7 On the other hand, complete absence of fuel in the anode compartment under load leads to the so called gross hydrogen starvation. This is typically triggered by the blockage of hydrogen gas inlets in an individual anode flow field by liquid water which, in order to sustain the cell current, leads to an anode potential increase up to a value at which water oxidation and carbon support corrosion can occur.8 Most importantly, unlike in the start-up/shut-down degradation discussed above, these hydrogen starvation issues are difficult to overcome by engineering solutions. Alternatively, material-based mitigation strategies include composite anode electrodes exhibiting high HOR and oxygen evolution reaction (OER) activity, as well as corrosion-resistant, non-carbon supported or even completely support-free catalysts. 9Inspired by the latter approach, an...

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Section: Resultssupporting

confidence: 91%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

Henning

Shimizu

Herranz

et al. 2018

J. Electrochem. Soc.

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“…6 Their homogenous nanoparticulate backbone acts beneficially regarding activities and selectivities in electrocatalytic reactions. 7,8 Furthermore, the noble metal character and the self-supported structure guarantee a higher (electro-)corrosive resistance and longer durability compared to commercial materials based on carbon. 9,10 Additionally, the engineering of the materials like varying the particle sizes or shapes or doping with transition metals is not quite exploited yet, but these measures would be promising to increase and to fit the performance to individual reactions.…”

Section: Introductionmentioning

confidence: 99%

A versatile ethanolic approach to metal aerogels (Pt, Pd, Au, Ag, Cu and Co)

Georgi

Klemmed

Benad

et al. 2019

Mater. Chem. Front.

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“…The effects of the size, shape, composition, and structure of the Pt-based aerogels on ORR electrocatalytic activity have been extensively explored. [62][63][64][65][66] Wire-based metallic aerogels derived from integrated nanoscale building blocks have been extensively investigated with the aim of achieving high electrical conductivity. The synthesis involves compositional and chemical tuning.…”

Section: Metallic Aerogel Electrocatalystsmentioning

confidence: 99%

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

Kim

et al. 2020

Advanced Materials

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oxidizing agent (oxygen). [4,5] Fuel cells are considered likely by many to play a central and integral role in future renewable energy developments. However, reducing their cost has been a significant challenge, and is critical for promoting future studies and accelerating market growth. [6-8] Currently, noble Pt materials are the most favored electrocatalysts for the electrochemical reactions at both the anode and cathode in fuel cells. The cathodic oxygen reduction reaction (ORR) rate is substantially slower than the anodic hydrogen oxidation reaction by several orders of magnitude. When properly tailored in electrodes, Pt materials provide fast reaction kinetics, good electrical conductivity, and high chemical stability in strongly acidic electrolytes. [9-11] Conventional electrocatalyst structures generally employ fine Pt powders (2-3 nm) supported on high surface area carbon (Pt/C). However, as the number of large scale energy applications continues to increase, the high required Pt loading (typically ≈0.5 mg cm −2 for commercial electrodes) and high cost of this precious metal (≈$1000 per troy ounce) pose significant barriers to the widespread use of fuel cells containing Pt materials. The quantity of Pt required to achieve the targeted electrode performance significantly contributes to the high cost of fuel cell systems. [12-14] In recent decades, significant efforts have been devoted to investigating the principles underlying the electrocatalyst layer, A new direction for developing electrocatalysts for hydrogen fuel cell systems has emerged, based on the fabrication of 3D architectures. These new architectures include extended Pt surface building blocks, the strategic use of void spaces, and deliberate network connectivity along with tortuosity, as design components. Various strategies for synthesis now enable the functional and structural engineering of these electrocatalysts with appropriate electronic, ionic, and electrochemical features. The new architectures provide efficient mass transport and large electrochemically active areas. To date, although there are few examples of fully functioning hydrogen fuel cell devices, these 3D electrocatalysts have the potential to achieve optimal cell performance and durability, exceeding conventional Pt powder (i.e., Pt/C) electrocatalysts. This progress report highlights the various 3D architectures proposed for Pt electrocatalysts, advances made in the fabrication of these structures, and the remaining technical challenges. Attempts to develop design rules for 3D architectures and modeling, provide insights into their achievable and potential performance. Perspectives on future developments of new multiscale designs are also discussed along with future study directions.

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Durability of Unsupported Pt-Ni Aerogels in PEFC Cathodes

Cited by 25 publications

References 62 publications

Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

A versatile ethanolic approach to metal aerogels (Pt, Pd, Au, Ag, Cu and Co)

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

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Durability of Unsupported Pt-Ni Aerogels in PEFC Cathodes

Cited by 25 publications

References 62 publications

Unsupported Pt3Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

Unsupported Pt3Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

A versatile ethanolic approach to metal aerogels (Pt, Pd, Au, Ag, Cu and Co)

Synergetic Structural Transformation of Pt Electrocatalyst into Advanced 3D Architectures for Hydrogen Fuel Cells

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Product

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About

Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions

Unsupported Pt₃Ni Aerogels as Corrosion Resistant PEFC Anode Catalysts under Gross Fuel Starvation Conditions