Influence of the dispersion state of ionomer on the dispersion of catalyst ink and the construction of catalyst layer

Yang, Daozeng; Guo, Yuqing; Tang, Haifeng; Wang, Yabo; Yang, Daijun; Ming, Pingwen; Zhang, Cunman; Li, Bing; Zhu, Shengli

doi:10.1016/j.ijhydene.2021.07.172

Cited by 21 publications

(9 citation statements)

References 61 publications

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“…Nafion ionomer is commonly employed in TF-RDE/RRDE studies as a dispersion for catalyst particles in catalyst ink as well as a binder to prevent the catalyst layer (CL) from peeling off the electrode surface. − The CL coated on the electrode surface is known to have a significant impact on the electrochemical performance . The key parameters that influence electrochemical characteristics are typically linked to the morphology of the catalyst ink, the coating technique, and the drying processes. , In diverse electrochemical processes, such as proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs), several authors have described the relevance of the ionomer in the catalyst ink with an optimal ionomer-to-catalyst ratio. − Due to the absence of contrast between Nafion and the catalyst particles, imaging the CL under a state-of-the-art electron microscope to obtain information on Nafion morphology and transport behavior is very challenging . As a result, electrochemical techniques have attracted more attention as an effective method to investigate and understand the CL’s interfacial mechanism and electrochemical behavior, revealing the function of the ionomer in the CL.…”

Section: Introductionmentioning

confidence: 99%

“… 35 , 36 In diverse electrochemical processes, such as proton exchange membrane fuel cells (PEMFCs) and anion exchange membrane fuel cells (AEMFCs), several authors have described the relevance of the ionomer in the catalyst ink with an optimal ionomer-to-catalyst ratio. 37 − 40 Due to the absence of contrast between Nafion and the catalyst particles, imaging the CL under a state-of-the-art electron microscope to obtain information on Nafion morphology and transport behavior is very challenging. 41 As a result, electrochemical techniques have attracted more attention as an effective method to investigate and understand the CL’s interfacial mechanism and electrochemical behavior, revealing the function of the ionomer in the CL.…”

Section: Introductionmentioning

confidence: 99%

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Indispensable Nafion Ionomer for High-Efficiency and Stable Oxygen Evolution Reaction in Alkaline Media

Kakati,

Anderson,

et al. 2023

ACS Appl. Mater. Interfaces

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Addressing the challenge of sluggish kinetics and limited stability in alkaline oxygen evolution reactions, recent exploration of novel electrochemical catalysts offers improved prospects. To expedite the assessment of these catalysts, a half-cell rotating disk electrode is often favored for its simplicity. However, the actual catalyst performance strongly depends on the fabricated catalyst layers, which encounter mass transport overpotentials. We systematically investigate the role and sequence of electrode drop-casting methods onto a glassy carbon electrode regarding the efficiency of the oxygen evolution reaction. The catalyst layer without Nafion experiences nearly 50% activity loss post stability test, while those with Nafion exhibit less than 5% activity loss. Additionally, the sequence of application of the catalyst and Nafion also shows a significant effect on catalyst stability. The catalyst activity increases by roughly 20% after the stability test when the catalyst layer is coated first with an ionomer layer, followed by drop-casting the catalysts. Based on the half-cell results, the Nafion ionomer not only acts as a binder in the catalyst layer but also enhances the interfacial interaction between the catalyst and electrolyte, promoting performance and stability. This study provides new insights into the efficient and accurate evaluation of electrocatalyst performance and stability as well as the role of Nafion ionomer in the catalyst layer.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Indispensable Nafion Ionomer for High-Efficiency and Stable Oxygen Evolution Reaction in Alkaline Media

Kakati,

Anderson,

et al. 2023

ACS Appl. Mater. Interfaces

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show abstract

“…The shear method can quickly destroy the flocculation structure in the slurry and then release the free water in the structure to reduce its viscosity . The ball milling method uses the collision and friction between zirconium beads and clusters to break the clusters. , The ultrasonic method generates microbubbles by ultrasonic waves and uses the impact force generated when bubbles burst to break clusters. − Yang et al found that increasing the main chain mobility of ionomer in solvent with water bath ultrasound increased the dissociation degree of −SO 3 H and the ζ potential of cluster surface, which improved the dispersion of clusters in the slurry, reduced the ohmic impedance and mass transfer impedance of MEA, increased the electrochemically active area, and increased the output voltage and power density of fuel cells. Du et al investigated the rheological properties of slurry prepared by ultrasonic waves and ball milling and reported that slurry prepared by the two dispersion processes had obvious shear thinning behavior besides different viscosity and thixotropy.…”

Section: Introductionmentioning

confidence: 99%

Effects of Electrostatic Force and Network Structure on the Stability of Proton-Exchange Membrane Fuel Cell Catalyst Ink

Xie

Guo

Yang

et al. 2023

ACS Appl. Mater. Interfaces

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The stability of the catalyst slurry of a protonexchange membrane fuel cell (PEMFC) is of great significance to its large-scale production and commercialization. In this study, three kinds of slurries with different stabilities were prepared using different probe ultrasonic powers. The influence of electrostatic force and network structure on slurry stability was also studied. In addition, the catalyst layer (CL) and membrane electrode assembly (MEA) were further tested to determine the relationship between slurry stability, CL, and MEA performance. The results showed that the slurry prepared with 600 W dispersion power had the least agglomeration on day 12, which is due to the clusters in the slurry having the smallest average particle size and the largest surface area, thereby allowing them to absorb the most Nafion and have the largest electrostatic force to inhibit agglomeration. However, the slurry with 1200 W dispersion power had the least sedimentation after 9.4 days because the strength of the network structure in the slurry strengthened the most, resulting in a significant increase in viscosity and inhibition of sedimentation. Electrochemical tests showed that the MEA gradually exhibited worse electrical performance and higher impedance due to the agglomeration of catalyst particles caused by the standing process. Altogether, this study provides insights to better understand and regulate the stability of catalyst slurries.

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Section: Introductionmentioning

confidence: 99%

“…This involves drying a catalyst ink that is a mixture of catalyst powders, ionomers, and water/alcohol solvent. Past studies have shown that the ionomer distribution is greatly influenced by the solvent composition 30,31 and the mixing method. 32 Although the ionomer distribution in mesoporous carbon is key for determining both the catalytic activity and the oxygentransport resistance, its details are unclear.…”

Section: ■ Introductionmentioning

confidence: 99%

Does an Ionomer Penetrate a Carbon Mesopore? Free-Energy Analysis Using Molecular Dynamics Simulations

Kikkawa

Jinnouchi

2022

J. Phys. Chem. C

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Mesoporous carbon support enhances the catalytic activity and gas diffusivity of the cathode catalyst layers of polymer-electrolyte fuel cells. The key role of the mesopores is believed to be their suppression of catalyst poisoning by the ionomers and reduction of the oxygen diffusivity near the catalysts. However, because of the difficulty to observe the ionomer distributions directly, it is unclear whether the ionomer penetrates the mesopores. Here, using molecular dynamics simulations of ionomer penetration into a seamless carbon mesopore, we show that the penetrability depends upon the pore size and the type of solvent. Free-energy profiles obtained from the simulations indicate that an ionomer in a water solvent easily invades a mesopore with a diameter >2 nm, while in a mixed water−ethanol solvent, it cannot do so. Structural differences between the two solvents suggest that three factors affect penetrability. Our results suggest that the ionomer distribution can be controlled by optimizing the solvent composition in the catalyst ink.

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Influence of the dispersion state of ionomer on the dispersion of catalyst ink and the construction of catalyst layer

Cited by 21 publications

References 61 publications

Indispensable Nafion Ionomer for High-Efficiency and Stable Oxygen Evolution Reaction in Alkaline Media

Indispensable Nafion Ionomer for High-Efficiency and Stable Oxygen Evolution Reaction in Alkaline Media

Effects of Electrostatic Force and Network Structure on the Stability of Proton-Exchange Membrane Fuel Cell Catalyst Ink

Does an Ionomer Penetrate a Carbon Mesopore? Free-Energy Analysis Using Molecular Dynamics Simulations

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