Improving Operational Robustness of NSTF Electrodes in PEM Fuel Cells

Kongkanand, Anusorn; Dioguardi, Matthew; Ji, Chunxin; Thompson, Eric L.

doi:10.1149/2.045208jes

Cited by 37 publications

(56 citation statements)

References 30 publications

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“…The lack of operational robustness can be attributed to the small electrode thickness and pore volume of NSTF electrodes. [16][17][18] The absence of ionomer in the metal-rich electrode makes the electrode very hydrophilic and susceptible to liquid water accumulation. It also causes relatively poor electrode proton conduction and inefficient Pt utilization.…”

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confidence: 99%

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Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Kongkanand¹,

Owejan²,

Moose³

et al. 2012

J. Electrochem. Soc.

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Ultrathin electrodes, such as the 3M Nanostructured Thin Film (NSTF) electrode, provide a plausible pathway to reduce platinum cost in low temperature fuel cells. However, several operational shortcomings, involving relatively poor electrode proton conduction and tendencies to collect water in the cathode, were observed in our fuel cell tests. This can be greatly mitigated when a few-micron thick dispersed-catalyst layer is placed adjacent to the NSTF layer, forming a dispersed-catalyst/NSTF hybrid electrode. This dispersedcatalyst layer is also called the "interlayer" because it is located between the NSTF layer and the microporous layer of the cathode diffusion medium. In this study, development of the hybrid electrode was pursued. Emphasis on developing lab-scale fabrication methods that can easily translate to roll-to-roll manufacturing process was a key element of the hybrid electrode development. The fuel cell performance of the electrode showed high sensitivity to fabrication methods. When the dispersed-catalyst layer was coated directly on the NSTF electrode, voltage at high current density dropped significantly. The voltage loss was surmised to be caused by ionomer seepage into the NSTF layer during the coating process. This voltage loss could be eliminated by placing the dispersedcatalyst layer on the gas-diffusion layer and then located adjacent to the NSTF cathode. Interaction between the dispersed-catalyst and NSTF layers and how it affects the fuel cell performance is discussed.In a proton exchange membrane fuel cell (PEMFC), Pt or Pt alloy nanoparticles supported on high surface area carbon particles are generally used in the cathode. The highly dispersed nature of the catalyst allows for good utilization of the precious metal. However, the electrochemical stability of the carbon support as well as the dissolution of Pt nanoparticles raise concerns about the durability of the catalyst. 1-4 3M's Nanostructured Thin Film (NSTF) is an extended surface catalyst which consists of a thin film of Pt alloy coated on individual lath-shaped single crystalline whiskers of an organic compound, perylene red (PR149). 5-7 The ∼0.5-1 μm long support whiskers are electrically non-conductive, thereby greatly reducing their susceptibility to electro-oxidative corrosion. The continuous layer of Pt serves as the electrical conductor for the electrode. Due to the low curvature (smaller number of low-coordination-number Pt atoms) and bulk-like characteristics of Pt in this form, NSTF electrodes exhibit higher chemical and electrochemical stability and 5-10 times higher Pt-areaspecific ORR activity than dispersed carbon supported catalysts. 7-10 In addition, owing to its unique structure of an extended surface of Pt covering a support, one expects that the Pt or Pt-alloy layer thickness (and therefore the Pt loading) could be reduced while maintaining the electrochemical properties of the catalyst. 11 Therefore, NSTF catalyst technology provides a plausible pathway for achieving higher ORR activity using small amounts of ...

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confidence: 99%

“…18 The layer is referred to as the interlayer (IL). Although the benefits of the IL were described, the great sensitivity of the preparation methods on the fuel cell performance was not discussed.…”

mentioning

confidence: 99%

Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Kongkanand¹,

Owejan²,

Moose³

et al. 2012

J. Electrochem. Soc.

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“…5a. As the performance loss under dry condition is also reported on the NSTF electrode, 27,28 this phenomenon appears common to ionomer-free electrodes.…”

Section: Cell Performance and Electrochemical Properties Under 80mentioning

confidence: 64%

Fabrication and Cell Analysis of a Pt/SiO₂Platinum Thin Film Electrode

Inaba

Suzuki

Hatanaka

et al. 2015

J. Electrochem. Soc.

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A platinum thin film electrode was fabricated on the surface of SiO 2 nanofibers by atomic layer deposition (ALD) and its cell performances were analyzed with an MEA using it as the cathode to reveal general features of platinum thin film electrodes. Although the Pt/SiO 2 cell showed comparable performance to the conventional Pt/C cell under suitable condition in spite of the much smaller electrochemical surface area (ECSA), it showed poor performance under overly dry or wet conditions as is the case with the 3M's nanostructured thin film (NSTF) electrode. An analysis applying a transmission line model of the electrode to the Pt/SiO 2 nanofiber electrode indicated that the performance loss of the Pt/SiO 2 electrode under dry condition is mainly due to the increase in the reaction resistance rather than that in the ohmic resistance. The increment in the reaction resistance was suppressed by addition of ionomer to the Pt/SiO 2 electrode. Furthermore, performance loss under wet condition due to cathode flooding was drastically alleviated by addition of a hydrophobic polymer to the Pt/SiO 2 electrode. A polymer electrolyte fuel cell (PEFC) is a promising power source for automotive application. For the wider commercialization of the fuel cell vehicles (FCVs), however, there still remains challenge to reduce the amount of precious Pt used as the electrocatalyst. For that purpose, it is essential to develop a novel electrode which enables high oxygen reduction reaction (ORR) activity, high durability, and high power density. 1,2Conventional PEFCs generally use platinum particles supported on high surface area carbon particles as electrode catalysts. Great efforts have been made in improving performance of those particulate catalysts by reducing particle size, 3 alloying, 4-9 or applying core-shell structure.10-12 However, the chemical and electrochemical stabilities of the carbon supports, 13,14 as well as the dissolution of platinum particles, [15][16][17] raise concern about the durability of the catalyst. Furthermore, the oxygen reduction reaction (ORR) activity per surface area of platinum (the specific activity) decreases with reducing the particle size.3,17-22 These problems limit further improvement of the dispersed catalysts.Recently, platinum thin film electrodes, such as 3M's nanostructured thin film (NSTF), have attracted much attention as alternative catalysts for PEFCs. 23 The structure of the NSTF electrode is totally different from that of the conventional Pt/C electrode in following three points: low platinum surface area (10 -25 cm 2 Pt /cm 2 planar ), support material without electrical conductivity, and containing no ionomer. Although NSTF electrodes showed higher efficiency and power density than conventional Pt/C electrodes under suitable operating conditions, 24,25 it has been reported that they tend to show larger performance loss under dry or wet conditions. [26][27][28] The aim of this research is to examine all those properties of NSTF on other thin film electrodes and reveal their general fe...

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“…[116] Additionally, under wet conditions (RH ≈ 100%) and temperatures below 60 °C (occurring, e.g., upon car start-up) NSTF cathode CLs have a propensity to flooding, restricting the access to reactants and leading to cell reversal. [105,116,117] These observations prove the need for an efficient water management to improve the operational robustness of such systems. Indeed, efforts to increase the proton conductivity and the water removal capability by coating the whiskers' surface with ionomer were undertaken, yielding only minor improvement in high current density performance, [117] possibly due to the simultaneous increase in O 2 mass transport resistance.…”

Section: Novel Catalyst Layer Conceptsmentioning

confidence: 93%

Nanostructuring Noble Metals as Unsupported Electrocatalysts for Polymer Electrolyte Fuel Cells

Cai

Henning

Herranz

et al. 2017

Advanced Energy Materials

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Two major challenges that impede fuel cell technology breakthrough are the insufficient activity of the electrocatalysts for the oxygen reduction reaction and their degradation during operation, caused by the potential‐induced corrosion of their carbon‐support upon fuel cell operation. Unsupported electrocatalysts derived from tailored noble‐metal nanostructures are superior to the conventional carbon‐supported Pt nanoparticle catalysts and address these barriers by fine‐tuning the surface composition and eliminating the support. Herein, recent efforts and achievements in the design, synthesis and characterization of unsupported electrocatalysts are reviewed, paying special attention to noble‐metal aerogels, nano/meso‐structured thin films and template‐derived metal nanoarchitectures. Their electrocatalytic performances for oxygen reduction are compared and discussed, and examples of successful catalyst transfer to polymer electrolyte fuel cells are highlighted. This report aims to demonstrate the potential and challenges of implementing unsupported catalysts in fuel cells, thereby providing a perspective on the further development of these materials.

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Improving Operational Robustness of NSTF Electrodes in PEM Fuel Cells

Cited by 37 publications

References 30 publications

Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Fabrication and Cell Analysis of a Pt/SiO₂Platinum Thin Film Electrode

Nanostructuring Noble Metals as Unsupported Electrocatalysts for Polymer Electrolyte Fuel Cells

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Improving Operational Robustness of NSTF Electrodes in PEM Fuel Cells

Cited by 37 publications

References 30 publications

Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Development of Dispersed-Catalyst/NSTF Hybrid Electrode

Fabrication and Cell Analysis of a Pt/SiO2Platinum Thin Film Electrode

Nanostructuring Noble Metals as Unsupported Electrocatalysts for Polymer Electrolyte Fuel Cells

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Fabrication and Cell Analysis of a Pt/SiO₂Platinum Thin Film Electrode