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2 pages, 149 KiB

Open AccessEditorial

Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis

by Jin-Soo Park

Energies 2021, 14(16), 5068; https://doi.org/10.3390/en14165068 - 18 Aug 2021

Cited by 2 | Viewed by 1466

Abstract

This book [...] Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

Research

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14 pages, 5028 KiB

Open AccessArticle

Composite Membranes Using Hydrophilized Porous Substrates for Hydrogen Based Energy Conversion

by Seohee Lim and Jin-Soo Park

Energies 2020, 13(22), 6101; https://doi.org/10.3390/en13226101 - 21 Nov 2020

Cited by 6 | Viewed by 1727

Abstract

Poly(tetrafluoroethylene) (PTFE) porous substrate-reinforced composite membranes for energy conversion technologies are prepared and characterized. In particular, we develop a new hydrophilic treatment method by in-situ biomimetic silicification for PTFE substrates having high porosity (60–80%) since it is difficult to impregnate ionomer into strongly [...] Read more.

Poly(tetrafluoroethylene) (PTFE) porous substrate-reinforced composite membranes for energy conversion technologies are prepared and characterized. In particular, we develop a new hydrophilic treatment method by in-situ biomimetic silicification for PTFE substrates having high porosity (60–80%) since it is difficult to impregnate ionomer into strongly hydrophobic PTFE porous substrates for the preparation of composite membranes. The thinner substrate having ~5 μm treated by the gallic acid/(3-trimethoxysilylpropyl)diethylenetriamine solution with the incubation time of 30 min shows the best hydrophilic treatment result in terms of contact angle. In addition, the composite membranes using the porous substrates show the highest proton conductivity and the lowest water uptake and swelling ratio. Membrane-electrode assemblies (MEAs) using the composite membranes (thinner and lower proton conductivity) and Nafion 212 (thicker and higher proton conductivity), which have similar areal resistance, are compared in I–V polarization curves. The I–V polarization curves of two MEAs in activation and Ohmic region are very identical. However, higher mass transport limitation is observed for Nafion 212 since the composite membrane with less thickness than Nafion 212 would result in higher back diffusion of water and mitigate cathode flooding. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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16 pages, 7468 KiB

Open AccessFeature PaperArticle

Pore-Filled Anion-Exchange Membranes with Double Cross-Linking Structure for Fuel Cells and Redox Flow Batteries

by Do-Hyeong Kim and Moon-Sung Kang

Energies 2020, 13(18), 4761; https://doi.org/10.3390/en13184761 - 11 Sep 2020

Cited by 8 | Viewed by 2376

Abstract

In this work, high-performance pore-filled anion-exchange membranes (PFAEMs) with double cross-linking structures have been successfully developed for application to promising electrochemical energy conversion systems, such as alkaline direct liquid fuel cells (ADLFCs) and vanadium redox flow batteries (VRFBs). Specifically, two kinds of porous [...] Read more.

In this work, high-performance pore-filled anion-exchange membranes (PFAEMs) with double cross-linking structures have been successfully developed for application to promising electrochemical energy conversion systems, such as alkaline direct liquid fuel cells (ADLFCs) and vanadium redox flow batteries (VRFBs). Specifically, two kinds of porous polytetrafluoroethylene (PTFE) substrates, with different hydrophilicities, were utilized for the membrane fabrication. The PTFE-based PFAEMs revealed, both excellent electrochemical characteristics, and chemical stability in harsh environments. It was proven that the use of a hydrophilic porous substrate is more desirable for the efficient power generation of ADLFCs, mainly owing to the facilitated transport of hydroxyl ions through the membrane, showing an excellent maximum power density of around 400 mW cm⁻² at 60 °C. In the case of VRFB, however, the battery cell employing the hydrophobic PTFE-based PFAEM exhibited the highest energy efficiency (87%, cf. AMX = 82%) among the tested membranes, because the crossover rate of vanadium redox species through the membrane most significantly affects the VRFB efficiency. The results imply that the properties of a porous substrate for preparing the membranes should match the operating environment, for successful applications to electrochemical energy conversion processes. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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14 pages, 2904 KiB

Open AccessArticle

Optimization of Perfluoropolyether-Based Gas Diffusion Media Preparation for PEM Fuel Cells

by Riccardo Balzarotti, Saverio Latorrata, Marco Mariani, Paola Gallo Stampino and Giovanni Dotelli

Energies 2020, 13(7), 1831; https://doi.org/10.3390/en13071831 - 10 Apr 2020

Cited by 9 | Viewed by 3157

Abstract

A hydrophobic perfluoropolyether (PFPE)-based polymer, namely Fluorolink^® P56, was studied instead of the commonly used polytetrafluoroethylene (PTFE), in order to enhance gas diffusion media (GDM) water management behavior, on the basis of a previous work in which such polymers had already proved [...] Read more.

A hydrophobic perfluoropolyether (PFPE)-based polymer, namely Fluorolink^® P56, was studied instead of the commonly used polytetrafluoroethylene (PTFE), in order to enhance gas diffusion media (GDM) water management behavior, on the basis of a previous work in which such polymers had already proved to be superior. In particular, an attempt to optimize the GDM production procedure and to improve the microporous layer (MPL) adhesion to the substrate was carried out. Materials properties have been correlated with production routes by means of both physical characterization and electrochemical tests. The latter were performed in a single PEM fuel cell, at different relative humidity (namely 80% on anode side and 60%/100% on cathode side) and temperature (60 °C and 80 °C) conditions. Additionally, electrochemical impedance spectroscopy measurements were performed in order to assess MPLs properties and to determine the influence of production procedure on cell electrochemical parameters. The durability of the best performing sample was also evaluated and compared to a previously developed benchmark. It was found that a final dipping step into PFPE-based dispersion, following MPL deposition, seems to improve the adhesion of the MPL to the macro-porous substrate and to reduce diffusive limitations during fuel cell operation. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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11 pages, 2498 KiB

Open AccessArticle

KOH-doped Porous Polybenzimidazole Membranes for Solid Alkaline Fuel Cells

by Jong-Hyeok Park and Jin-Soo Park

Energies 2020, 13(3), 525; https://doi.org/10.3390/en13030525 - 21 Jan 2020

Cited by 11 | Viewed by 2984

Abstract

In this study the preparation and properties of potassium hydroxide-doped meta-polybenzimidazole membranes with 20–30 μm thickness are reported as anion conducting polymer electrolyte for application in fuel cells. Dibutyl phthalate as porogen forms an asymmetrically porous structure of membranes along thickness direction. One [...] Read more.

In this study the preparation and properties of potassium hydroxide-doped meta-polybenzimidazole membranes with 20–30 μm thickness are reported as anion conducting polymer electrolyte for application in fuel cells. Dibutyl phthalate as porogen forms an asymmetrically porous structure of membranes along thickness direction. One side of the membranes has a dense skin layer surface with 1.5–15 μm and the other side of the membranes has a porous one. It demonstrated that ion conductivity of the potassium hydroxide-doped porous membrane with the porogen content of 47 wt.% (0.090 S cm⁻¹), is 1.4 times higher than the potassium hydroxide-doped dense membrane (0.065 S cm⁻¹). This is because the porous membrane allows 1.4 times higher potassium hydroxide uptake than dense membranes. Tensile strength and elongation studies confirm that doping by simply immersing membranes in potassium hydroxide solutions was sufficient to fill in the inner pores. The membrane-electrode assembly using the asymmetrically porous membrane with 1.4 times higher ionic conductivity than the dense non-doped polybenzimidazole (mPBI) membrane showed 1.25 times higher peak power density. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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9 pages, 2438 KiB

Open AccessArticle

Innovative Membrane Electrode Assembly (MEA) Fabrication for Proton Exchange Membrane Water Electrolysis

by Guo-Bin Jung, Shih-Hung Chan, Chun-Ju Lai, Chia-Chen Yeh and Jyun-Wei Yu

Energies 2019, 12(21), 4218; https://doi.org/10.3390/en12214218 - 5 Nov 2019

Cited by 9 | Viewed by 5565

Abstract

In order to increase the hydrogen production rate as well as ozone production at the anode side, increased voltage application and more catalyst utilization are necessary. The membrane electrode assembly (MEA) produces hydrogen/ozone via proton exchange membrane water electrolysis (PEMWE)s which gives priority [...] Read more.

In order to increase the hydrogen production rate as well as ozone production at the anode side, increased voltage application and more catalyst utilization are necessary. The membrane electrode assembly (MEA) produces hydrogen/ozone via proton exchange membrane water electrolysis (PEMWE)s which gives priority to a coating method (abbreviation: ML). However, coating takes more effort and is labor-consuming. This study will present an innovative preparation method, known as flat layer (FL), and compare it with ML. FL can significantly reduce efforts and largely improve MEA production. Additionally, MEA with the FL method is potentially durable compared to ML. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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14 pages, 9187 KiB

Open AccessFeature PaperArticle

Liquid Water Transport in Porous Metal Foam Flow-Field Fuel Cells: A Two-Phase Numerical Modelling and Ex-Situ Experimental Study

by Ashley Fly, Kyoungyoun Kim, John Gordon, Daniel Butcher and Rui Chen

Energies 2019, 12(7), 1186; https://doi.org/10.3390/en12071186 - 27 Mar 2019

Cited by 18 | Viewed by 4893

Abstract

Proton exchange membrane fuel cells (PEMFCs) using porous metallic foam flow-field plates have been demonstrated as an alternative to conventional rib and channel designs, showing high performance at high currents. However, the transport of liquid product water through metal foam flow-field plates in [...] Read more.

Proton exchange membrane fuel cells (PEMFCs) using porous metallic foam flow-field plates have been demonstrated as an alternative to conventional rib and channel designs, showing high performance at high currents. However, the transport of liquid product water through metal foam flow-field plates in PEMFC conditions is not well understood, especially at the individual pore level. In this work, ex-situ experiments are conducted to visualise liquid water movement within a metal foam flow-field plate, considering hydrophobicity, foam pore size and air flow rate. A two-phase numerical model is then developed to further investigate the fundamental water transport behaviour in porous metal foam flow-field plates. Both the experimental and numerical work demonstrate that unlike conventional PEMFC channels, air flow rate does not have a strong influence on water removal due to the high surface tensions between the water and foam pore ligaments. A hydrophobic foam was seen to transport liquid water away from the initial injection point faster than a hydrophilic foam. In ex-situ tests, liquid water forms and maintains a random preferential pathway until the flow-field edge is reached. These results suggest that controlled foam hydrophobicity and pore size is the best way of managing water distribution in PEMFCs with porous flow-field plates. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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17 pages, 2447 KiB

Open AccessArticle

Gas Diffusion Layers in Fuel Cells and Electrolysers: A Novel Semi-Empirical Model to Predict Electrical Conductivity of Sintered Metal Fibres

by Reza Omrani and Bahman Shabani

Energies 2019, 12(5), 855; https://doi.org/10.3390/en12050855 - 5 Mar 2019

Cited by 16 | Viewed by 3326

Abstract

This paper introduces novel empirical as well as modified models to predict the electrical conductivity of sintered metal fibres and closed-cell foams. These models provide a significant improvement over the existing models and reduce the maximum relative error from as high as just [...] Read more.

This paper introduces novel empirical as well as modified models to predict the electrical conductivity of sintered metal fibres and closed-cell foams. These models provide a significant improvement over the existing models and reduce the maximum relative error from as high as just over 30% down to about 10%. Also, it is shown that these models provide a noticeable improvement for closed-cell metal foams. However, the estimation of electrical conductivity of open-cell metal foams was improved marginally over previous models. Sintered porous metals are widely used in electrochemical devices such as water electrolysers, unitised regenerative fuel cells (URFCs) as gas diffusion layers (GDLs), and batteries. Having a more accurate prediction of electrical conductivity based on variation by porosity helps in better modelling of such devices and hence achieving improved designs. The models presented in this paper are fitted to the experimental results in order to highlight the difference between the conductivity of sintered metal fibres and metal foams. It is shown that the critical porosity (maximum achievable porosity) can play an important role in sintered metal fibres to predict the electrical conductivity whereas its effect is not significant in open-cell metal foams. Based on the models, the electrical conductivity reaches zero value at 95% porosity rather than 100% for sintered metal fibres. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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10 pages, 3063 KiB

Open AccessArticle

Effect of Dispersion Solvents in Catalyst Inks on the Performance and Durability of Catalyst Layers in Proton Exchange Membrane Fuel Cells

by Chan-Ho Song and Jin-Soo Park

Energies 2019, 12(3), 549; https://doi.org/10.3390/en12030549 - 11 Feb 2019

Cited by 26 | Viewed by 6106

Abstract

Five different ionomer dispersions using water–isopropanol (IPA) and N-methylpyrrolidone (NMP) were investigated as ionomer binders for catalyst layers in proton exchange membrane fuel cells. The distribution of ionomer plays an important role in the design of high-performance porous electrode catalyst layers since [...] Read more.

Five different ionomer dispersions using water–isopropanol (IPA) and N-methylpyrrolidone (NMP) were investigated as ionomer binders for catalyst layers in proton exchange membrane fuel cells. The distribution of ionomer plays an important role in the design of high-performance porous electrode catalyst layers since the transport of species, such as oxygen and protons, is controlled by the thickness of the ionomer on the catalyst surface and the continuity of the ionomer and gas networks in the catalyst layer, with the transport of electrons being related to the continuity of the carbon particle network. In this study, the effect of solvents in ionomer dispersions on the performance and durability of catalyst layers (CLs) is investigated. Five different types of catalyst inks were used: (i) ionomer dispersed in NMP; (ii) ionomer dispersed in water–IPA; (iii) ionomer dispersed in NMP, followed by adding water–IPA; (iv) ionomer dispersed in water–IPA, followed by adding NMP; and (v) a mixture of ionomer dispersed in NMP and ionomer dispersed in water–IPA. Dynamic light scattering of the five dispersions showed different average particles sizes: ~0.40 μm for NMP, 0.91–1.75 μm for the mixture, and ~2.02 μm for water–IPA. The membrane-electrode assembly prepared from an ionomer dispersion with a larger particle size (i.e., water–IPA) showed better performance, while that prepared from a dispersion with a smaller particle size (i.e., NMP) showed better durability. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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10 pages, 2109 KiB

Open AccessArticle

Experimental Studies of Effect of Land Width in PEM Fuel Cells with Serpentine Flow Field and Carbon Cloth

by Xuyang Zhang, Andrew Higier, Xu Zhang and Hongtan Liu

Energies 2019, 12(3), 471; https://doi.org/10.3390/en12030471 - 1 Feb 2019

Cited by 34 | Viewed by 4189

Abstract

Flow field plays an important role in the performance of proton exchange membrane (PEM) fuel cells, such as transporting reactants and removing water products. Therefore, the performance of a PEM fuel cell can be improved by optimizing the flow field dimensions and designs. [...] Read more.

Flow field plays an important role in the performance of proton exchange membrane (PEM) fuel cells, such as transporting reactants and removing water products. Therefore, the performance of a PEM fuel cell can be improved by optimizing the flow field dimensions and designs. In this work, single serpentine flow fields with four different land widths are used in PEM fuel cells to study the effects of the land width. The gas diffusion layers are made of carbon cloth. Since different land widths may be most suitable for different reactant flow rates, three different inlet flow rates are studied for all the flow fields with four different land widths. The effects of land width and inlet flow rate on fuel cell performance are studied based on the polarization curves and power densities. Without considering the pumping power, the cell performance always increases with the decrease in the land width and the increase in the inlet flow rates. However, when taking into consideration the pumping power, the net power density reaches the maximum at different combinations of land widths and reactant flow rates at different cell potentials. Full article

(This article belongs to the Special Issue Hydrogen-Based Energy Conversion: Polymer Electrolyte Fuel Cells and Electrolysis)

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