Possible scenario of forming a catalyst layer for proton exchange membrane fuel cells

Zeng, Rong; Zhang, H. Y.; Liang, Shuai; Wang, L. G.; Jiang, Lijun; Liu, X. P.

doi:10.1039/c9ra09864j

Cited by 6 publications

(6 citation statements)

References 30 publications

(44 reference statements)

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“…(1) ionomer-covered carbon support surface, (2) ionomercovered Pt catalyst surface, and (3) packed free ionomer between the aggregated Pt/C particles. 29 For the catalyst layer with an additional PDMS film, the PDMS film can be deposited on both the ionomer-covered and uncovered regions of the carbon and the Pt surface, as well as between the aggregated Pt/ C particles. By comparing the volume of the PDMS film with the Nafion film, the relative thickness of the PDMS films to the thickness of Nafion film can be estimated.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…To examine these phenomena in detail, it is necessary to consider the change in the electrode structure and characteristics due to the PDMS. In the electrode, the ionomer coverage can be divided into three parts: (1) ionomer-covered carbon support surface, (2) ionomer-covered Pt catalyst surface, and (3) packed free ionomer between the aggregated Pt/C particles . For the catalyst layer with an additional PDMS film, the PDMS film can be deposited on both the ionomer-covered and uncovered regions of the carbon and the Pt surface, as well as between the aggregated Pt/C particles.…”

Section: Resultsmentioning

confidence: 99%

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Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells

Yeon

Jang

Choi

et al. 2021

ACS Appl. Mater. Interfaces

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The catalyst layer’s high durability is essential in commercializing polymer electrolyte membrane fuel cells (PEMFCs), particularly for vehicle applications, because their frequent on/off operation can induce carbon corrosion, which affects surface properties and morphological characteristics of the carbon and results in aggregation and detachment of Pt nanoparticles on the carbon surface. Herein, to address the carbon corrosion problem while delivering a high-performance PEMFC, polydimethylsiloxane (PDMS) with high gas permeability, chemical stability, and hydrophobicity was employed to protect the catalyst layer from carbon corrosion and improve the mass transport. Because the catalyst slurry using alcohol-based solvents showed low compatibility with nonpolar solvents of the PDMS solution, a parallel two-nozzle system with separated solution reservoirs was developed by modifying a conventional three-dimensional printing machine. To determine the optimal PDMS amount in the cathode catalyst layer, PDMS solution concentration was varied by quantitatively controlling the PDMS amount coated on the electrode layer. Finally, the PEMFC with the PDMS-modified cathode of 0.1 mgPDMS cm–2 loading showed enhanced durability due to increased electrochemical surface and maximum power density by 37.2 and 21.7%, respectively, after the accelerated stress test. Furthermore, an improvement in the initial performance from enhanced water management was observed compared to those of PEMFCs with a conventional electrode.

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Section: ■ Results and Discussionmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells

Yeon

Jang

Choi

et al. 2021

ACS Appl. Mater. Interfaces

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show abstract

“…[77][78][79][80] The degree of dispersion can reach from fully lumped ionomer too perfectly dispersed ionomer, with the optimum to be found in-between. 81 The authors will address the resulting heterogeneities in ionomer coverage in a follow-up work, accounting for additional structural parameters, such as component and void fractions, ionomer dispersion and coverage, and the porous network properties. Based on this treatment, a description of mixed wettability will be possible that aligns well with previous works that employed continuous distributions of contact angles.…”

Section: Understanding Platinum Loading Reduction and Catalyst Layer ...mentioning

confidence: 99%

Review—Wetting Phenomena in Catalyst Layers of PEM Fuel Cells: Novel Approaches for Modeling and Materials Research

Olbrich

Kadyk

Sauter

et al. 2022

J. Electrochem. Soc.

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The development of high-performance polymer electrolyte fuel cells increasingly relies on modeling to optimally tune cathode catalyst layers (CCL) to desired properties. This includes models to rationalize the role of water as a promoter and asphyxiant to the oxygen reduction reaction. Existing models are able to reproduce or predict, using assumed parameters, the performance of the cell. However, consideration of the wetting properties of the composite has remained elusive. Experiments to characterize these properties are difficult to perform. There is thus a gap in theory for relating material choices with wetting properties. Here we elaborate on this gap and presents a novel conceptual approach to close it. Fundamental modeling approaches, molecular dynamics studies, and experimental works have shown that the interaction of ionomer with the Pt/C surface exerts a major impact on wetting behavior and water sorption properties of the porous CCL composite. In our approach, the state of molecular alignment of ionomer sidechains and backbones is linked to the structural characteristics of the Pt/C catalyst. From this rationalization, wetting properties of the CCL can be deduced. An analysis of these correlations supports a crucial hypothesis: lowering the platinum loading leaves the CCL more prone to flooding.

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“…Closer examination of this agglomerate structure and of the ionomer morphology revealed that typically the ionomer film is unevenly distributed 21 – 24 , i.e., its coverage and thickness can vary significantly. Additionally, large ionomer aggregates that are not part of the thin film have been observed 24 – 26 . These variations in ionomer morphology largely impact the percolation behavior of the ionomer network and thus the proton conductivity of the CCL, as well as the volume fraction and network properties of gas-filled pores needed for oxygen supply 27 – 29 .…”

Section: Introductionmentioning

confidence: 99%

Structure and conductivity of ionomer in PEM fuel cell catalyst layers: a model-based analysis

Olbrich,

Kadyk,

Sauter

et al. 2023

Sci Rep

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Efforts in design and optimization of catalyst layers for polymer electrolyte fuel cells hinge on mathematical models that link electrode composition and microstructure with effective physico-chemical properties. A pivotal property of these layers and the focus of this work is the proton conductivity, which is largely determined by the morphology of the ionomer. However, available relations between catalyst layer composition and proton conductivity are often adopted from general theories for random heterogeneous media and ignore specific features of the microstructure, e.g., agglomerates, film-like structures, or the hierarchical porous network. To establish a comprehensive understanding of the peculiar structure-property relations, we generated synthetic volumetric images of the catalyst layer microstructure. In a mesoscopic volume element, we modeled the electrolyte phase and calculated the proton conductivity using numerical tools. Varying the ionomer morphology in terms of ionomer film coverage and thickness revealed two limiting cases: the ionomer can either form a thin film with high coverage on the catalyst agglomerates; or the ionomer exists as voluminous chunks that connect across the inter-agglomerate space. Both cases were modeled analytically, adapting relations from percolation theory. Based on the simulated data, a novel relation is proposed, which links the catalyst layer microstructure to the proton conductivity over a wide range of morphologies. The presented analytical approach is a versatile tool for the interpretation of experimental trends and it provides valuable guidance for catalyst layer design. The proposed model was used to analyze the formation of the catalyst layer microstructure during the ink stage. A parameter study of the initial ionomer film thickness and the ionomer dispersion parameter revealed that the ionomer morphology should be tweaked towards well-defined films with high coverage of catalyst agglomerates. These implications match current efforts in the experimental literature and they may thus provide direction in electrode materials research for polymer electrolyte fuel cells.

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Possible scenario of forming a catalyst layer for proton exchange membrane fuel cells

Abstract: Ionomer in the catalyst layer provides an ion transport channel which is essential for many electrochemical devices.

Cited by 6 publications

References 30 publications

Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells

Layer-by-Layer Polydimethylsiloxane Modification Using a Two-Nozzle Spray Process for High Durability of the Cathode Catalyst in Proton-Exchange Membrane Fuel Cells

Review—Wetting Phenomena in Catalyst Layers of PEM Fuel Cells: Novel Approaches for Modeling and Materials Research

Structure and conductivity of ionomer in PEM fuel cell catalyst layers: a model-based analysis

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