Exceptional Oxygen Reduction Reaction Activity and Durability of Platinum–Nickel Nanowires through Synthesis and Post-Treatment Optimization

Alia, Shaun M; Ngo, Chilan; Shulda, Sarah; Ha, Mai‐Anh; Dameron, Arrelaine A.; Weker, Johanna Nelson; Neyerlin, Kenneth C.; Kocha, Shyam S.; Pylypenko, Svitlana; Pivovar, Bryan S.

doi:10.1021/acsomega.7b00054

Cited by 56 publications

(123 citation statements)

References 56 publications

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“…In previous RDE measurements we have observed losses in ECA and specific activity associated with Ni loss from ex-situ acid leaching prior to testing, which is due to a dealloying effect. 37 This is consistent with measurements of PtNi NSTF, which have also showed that Ni loss from the core of the material resulted in decreased activity. 9 We have found that PtNiNWs lose less Ni during RDE testing than the MEAs presented here, which may explain some of this large difference.…”

Section: Resultssupporting

confidence: 90%

“…37,38 The PtNiNW materials used as the basis for this work have demonstrated exceptionally high mass activity and electrochemical surface area (ECA) in rotating disc electrode (RDE) studies of inherent catalytic properties. 37,39 We commonly refer to these catalyst structures as nanowires, although on many occasions the transition metal core has been removed and they could alternatively be referred to as nanotubes. The nanowires we have investigated generally are up to 10's of microns in length (as-synthesized) with diameters typically between 100-300 nm.…”

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confidence: 99%

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Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Mauger

Neyerlin

Alia

et al. 2018

J. Electrochem. Soc.

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Platinum-nickel nanowire (PtNiNW) catalysts have shown exceptionally high oxygen reduction mass activity in rotating disk electrode measurements. However, the ability to successfully incorporate PtNiNWs into high performance membrane electrode assemblies (MEAs) has been challenging due to their size, shape, density, dispersion characteristics, and corrosion-susceptible nickel core. We have investigated the impact of specific processing steps and electrode composition on observed fuel cell performance and electrochemical properties in order to optimize performance. We have found that nickel ion contamination is a major concern for PtNiNWs that can be addressed through ion exchange in fabricated/tested MEAs or by acid leaching of catalyst materials prior to MEA incorporation, with the latter being the more successful method. Additionally, decreased ionomer incorporation has led to the highest performance demonstrating 238 mA/mg Pt (0.9 V IR-free) for PtNiNWs (pre-leached to 80 wt% Pt) with 9 wt% ionomer incorporation. Platinum (and Pt alloy) nanoparticles on carbon supports (Pt/C) are the standard catalysts for polymer electrolyte fuel cells (PEMFCs). They are the basis for the thousands of fuel cell vehicles on the road today as well as tens of thousands of stationary polymer electrolyte fuel cell power systems. The performance of membrane electrode assemblies (MEAs) based on Pt/C has been optimized over multiple decades through tuning several parameters including carbon type, Pt to carbon loading, ionomer content/type, ink solvent composition, and coating/drying parameters.1-6 The implementation of unsupported metal catalysts in PEMFCs has seen much less investigation, and the application of non-Pt/C catalysts often falls back on the processes and compositions that have been optimized for Pt/C. For materials, like the nanowires presented here, it should not come as a surprise that dramatic differences in size/structure and properties (density, dispersability, magnetism, surface conductivity, ionomer interactions) significantly impact electrode performance and there is a need to investigate alternate, optimized fabrication compositions and approaches.To date, the motivation for the development and application of extended surface electrocatalysts in fuel cells has come largely from the promising work of 3M's nanostructured thin film (NSTF) materials. 7,8 These materials started as Pt thin films, but over the last several years have shifted to PtNi alloys, with much effort devoted to examining the sensitivity of activity to the alloy's composition.9,10 3M's NSTF is unique in that it is fabricated on a substrate and hot pressed directly into the membrane to form a MEA. Poly/single crystal studies of inherent catalytic activity and durability of flat metal surfaces further show significant benefits over nanoparticle catalysts consistent with findings of NSTF.11-13 The advantages of extended surface catalyst over supported nanoparticle catalysts are still a matter of some debate, but have been attributed to a number o...

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Section: Resultssupporting

confidence: 90%

mentioning

confidence: 99%

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Mauger

Neyerlin

Alia

et al. 2018

J. Electrochem. Soc.

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“…To further improve its stability under normal PEFC operation, future work will focus on tuning the aerogel nanochain structure and surface vs. bulk composition, as to minimize Ni dissolution from the alloy catalyst. 61 …”

Section: Discussionmentioning

confidence: 99%

Durability of Unsupported Pt-Ni Aerogels in PEFC Cathodes

Henning

Herranz

Ishikawa

et al. 2017

J. Electrochem. Soc.

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The commercial success of polymer electrolyte fuel cells (PEFCs) depends on the development of Pt-based oxygen reduction reaction (ORR) catalysts with greater activity and stability to reduce the amount of expensive noble metal per device. To advance toward this goal, we have tested a novel class of unsupported bimetallic alloy catalysts (aerogels) as the cathode material in PEFCs under two accelerated stress test conditions and compared it to a state-of-the-art carbon-supported benchmark (Pt/C). The investigated Pt 3 Ni aerogel shows little degradation under high potential conditions (> 1.0 V) which can occur during fuel starvation and start-up/shutdown of the cell. If tested under the same conditions, the Pt/C benchmark displays significant losses of electrochemical surface area and ORR activity due to carbon support corrosion as observed in cross section and transmission electron microscopy analysis. When testing the durability upon extended load cycling (0.6-1.0 V), Pt 3 Ni aerogel demonstrates less stability than Pt/C which is related to the severe Ni leaching from the alloy under such conditions. These findings highlight the advantages of using unsupported ORR catalysts in PEFCs and point to the reduction of non-noble metal dissolution as the next development step. Polymer electrolyte fuel cells (PEFCs) currently rely on large amounts of carbon-supported platinum (Pt/C) catalysts (≈0.4 mg Pt /cm 2 electrode ) to reduce the voltage losses due to the sluggish kinetics of the cathodic oxygen reduction reaction (ORR).1 Recent advancements in minimizing the Pt loading and associated costs were achieved by alloying platinum with other metals like Ni, Cu and Co which increases the Pt mass-specific ORR activity.2 On the other hand, these catalysts suffer from significant corrosion of the carbon support and Pt nanoparticles during PEFC operation which compromises their long-term efficiency and reliability.3 To specifically mitigate the issue of support stability, researchers have developed alternative corrosionresistant supports (e.g. conductive metal oxides 4-7 ), extended metal surfaces (e.g. 3 M nanostructured thin film catalysts 8 ) and unsupported materials (e.g. Pt-coated Ni, Co or Cu nanowires 9-11 ). Pursuing this last strategy, unsupported bimetallic Pt-Ni electrocatalysts with high specific surface area (≈30 m 2 /g Pt ) and nanochain network structure, referred to as aerogels, were synthesized in a previous work. 12These materials reach the U.S. Department of Energy target (DOE; i.e. 440 A/g Pt at 0.9 V vs. the reversible hydrogen electrode (V RHE )) for automotive PEFC application when tested as thin films by the rotating disk electrode (RDE) technique, 13 which is the standard tool employed by the majority of researchers in this field for initial assessment of catalyst activities. Considering that performance figures derived from such RDE experiments, often do not translate fully to the technical system, it is fundamental to also assess activity and durability in PEFCs to evaluate the real application p...

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“…Nanocatalysts with superior ORR activity, such as nanostructured and mesostructured thin films, Pt and PtNi nanowires, PtM aerogels and hollow PtM NPs,, have recently been synthesized. A record ORR specific activity of 11.5 mA cm −2 Pt at 0.90 V vs .…”

Section: Oxygen Reduction Reaction Electrocatalysis In Acidic Electromentioning

confidence: 99%

A Review on Recent Developments and Prospects for the Oxygen Reduction Reaction on Hollow Pt‐alloy Nanoparticles

et al. 2018

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Due to their interesting electrocatalytic properties for the oxygen reduction reaction (ORR), hollow Pt-alloy nanoparticles (NPs) supported on high-surface-area carbon attract growing interest. However, the suitable synthesis methods and associated mechanisms of formation, the reasons for their enhanced specific activity for the ORR, and the nature of adequate alloying elements and carbon supports for this type of nanocatalysts remain open questions. This Review aims at shedding light on these topics with a special emphasis on hollow PtNi NPs supported onto Vulcan C (PtNi/C). We first show how hollow Pt-alloy/C NPs can be synthesized by a mechanism involving galvanic replacement and the nanoscale Kirkendall effect. Nickel, cobalt, copper, zinc, and iron (Ni, Co, Cu, Zn, and Fe, respectively) were tested for the formation of Pt-alloy/C hollow nanostructures. Our results indicate that metals with standard potential -0.4

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Exceptional Oxygen Reduction Reaction Activity and Durability of Platinum–Nickel Nanowires through Synthesis and Post-Treatment Optimization

Cited by 56 publications

References 56 publications

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Fuel Cell Performance Implications of Membrane Electrode Assembly Fabrication with Platinum-Nickel Nanowire Catalysts

Durability of Unsupported Pt-Ni Aerogels in PEFC Cathodes

A Review on Recent Developments and Prospects for the Oxygen Reduction Reaction on Hollow Pt‐alloy Nanoparticles

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