Preparation of MEA for PEM fuel cell by hot press process

Kód výsledku v IS VaVaI

<a href="https://www.isvavai.cz/riv?ss=detail&h=RIV%2F60461373%3A22310%2F18%3A43916123" target="_blank" >RIV/60461373:22310/18:43916123 - isvavai.cz</a>

Nalezeny alternativní kódy

RIV/60461373:22310/18:43916124

Výsledek na webu

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DOI - Digital Object Identifier

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Jazyk výsledku

angličtina

Název v původním jazyce

Preparation of MEA for PEM fuel cell by hot press process

Popis výsledku v původním jazyce

On of the key components of the PEM fuel cell stack is the membrane-electrode assembly (MEA). MEA composed from a polymer electrolyte membrane and gas diffusion electrodes containing catalytic layer (GDE). The performance of a MEA depends critically on the conductivity of membrane and activity of the catalytic layer. GDE can be based on carbon cloth, or on carbon paper. Both materials have a different level of porosity, electric conductivity and mechanical properties. Their selection strongly depends mainly on the membrane properties. Catalytic layer is mechanically stabilized by Nafion binder creating at the same time three-phase contact. Prepared electrodes can be assembled with the membrane either directly in the fuel cell, or by pressing them onto each side of proton exchange membrane under high pressure and temperature (hot-pressed MEA). The method of the MEA preparation plays an important role in the final performance of fuel cell. Different properties of electrodes and different membrane materials, as well as parameters of MEA fabrication represent a broad field for optimization. In the present study, the impact of membrane thickness and material on fuel cell performance and water management was investigated. Membranes commercially available under name Nafion, Fumapem and CTPEM were used. Porosity and wettability of electrode material have a crucial influence on transport properties of electrodes for water and gases. Carbon paper is representative of low porosity and ohmic resistance material characterized by high rigidness. On the other hand, carbon cloth represents material with high porosity, ohmic resistance and flexibility. These parameters may influence stability of the gas diffusion electrode during pressing. Carbon paper is more sensitive to string compression than carbon cloth. Therefore, homogeneous contact between electrode and bipolar plate in whole area electrode area may be unsafe. This is also a reason why in the case of using carbon paper as GDE material, requirements on sealing of the cell increase. Alternative solution of this problem represent addition of woven material based on carbon fibers on the back side of the carbon paper and thus to prepare sort of hybrid carbon paper/cloth GDE. Another issue represents glass transition temperature of the membrane. It has to be approached during hot-pressing to connect well the catalytic layer and membrane. Increasing time of the hold-up at this temperature improves the ionic contact between these two components. At the same time, it affects internal structure of the polymer and subsequently ionic conductivity of the membrane on one side and its permeability to hydrogen on the other side. Second problem represent risk of damage of membrane by electrodes during application of hot-press. Membranes with thickness less than 150 µm, have an insufficient mechanical properties and it is easy to perforate them. This problem can be solved by using reinforced membranes. Unfortunately, fibers of polytetrafluoroethylene are distributed in mass of membrane not fully homogeneously. They thus cause spontaneous rolling of membranes resulting again in imperfect contact between the electrode and membrane. The target of this study is to provide more insight into above-mentioned problems for the selected membranes.

Název v anglickém jazyce

Preparation of MEA for PEM fuel cell by hot press process

Popis výsledku anglicky

On of the key components of the PEM fuel cell stack is the membrane-electrode assembly (MEA). MEA composed from a polymer electrolyte membrane and gas diffusion electrodes containing catalytic layer (GDE). The performance of a MEA depends critically on the conductivity of membrane and activity of the catalytic layer. GDE can be based on carbon cloth, or on carbon paper. Both materials have a different level of porosity, electric conductivity and mechanical properties. Their selection strongly depends mainly on the membrane properties. Catalytic layer is mechanically stabilized by Nafion binder creating at the same time three-phase contact. Prepared electrodes can be assembled with the membrane either directly in the fuel cell, or by pressing them onto each side of proton exchange membrane under high pressure and temperature (hot-pressed MEA). The method of the MEA preparation plays an important role in the final performance of fuel cell. Different properties of electrodes and different membrane materials, as well as parameters of MEA fabrication represent a broad field for optimization. In the present study, the impact of membrane thickness and material on fuel cell performance and water management was investigated. Membranes commercially available under name Nafion, Fumapem and CTPEM were used. Porosity and wettability of electrode material have a crucial influence on transport properties of electrodes for water and gases. Carbon paper is representative of low porosity and ohmic resistance material characterized by high rigidness. On the other hand, carbon cloth represents material with high porosity, ohmic resistance and flexibility. These parameters may influence stability of the gas diffusion electrode during pressing. Carbon paper is more sensitive to string compression than carbon cloth. Therefore, homogeneous contact between electrode and bipolar plate in whole area electrode area may be unsafe. This is also a reason why in the case of using carbon paper as GDE material, requirements on sealing of the cell increase. Alternative solution of this problem represent addition of woven material based on carbon fibers on the back side of the carbon paper and thus to prepare sort of hybrid carbon paper/cloth GDE. Another issue represents glass transition temperature of the membrane. It has to be approached during hot-pressing to connect well the catalytic layer and membrane. Increasing time of the hold-up at this temperature improves the ionic contact between these two components. At the same time, it affects internal structure of the polymer and subsequently ionic conductivity of the membrane on one side and its permeability to hydrogen on the other side. Second problem represent risk of damage of membrane by electrodes during application of hot-press. Membranes with thickness less than 150 µm, have an insufficient mechanical properties and it is easy to perforate them. This problem can be solved by using reinforced membranes. Unfortunately, fibers of polytetrafluoroethylene are distributed in mass of membrane not fully homogeneously. They thus cause spontaneous rolling of membranes resulting again in imperfect contact between the electrode and membrane. The target of this study is to provide more insight into above-mentioned problems for the selected membranes.

Druh

O - Ostatní výsledky

CEP obor

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OECD FORD obor

10405 - Electrochemistry (dry cells, batteries, fuel cells, corrosion metals, electrolysis)

Projekt

<a href="/cs/project/VI20152019018" target="_blank" >VI20152019018: Vývoj a realizace nezávislého DC zdroje napájení s vodíkovým palivovým článkem</a><br>

Návaznosti

P - Projekt vyzkumu a vyvoje financovany z verejnych zdroju (s odkazem do CEP)

Rok uplatnění

2018

Kód důvěrnosti údajů

S - Úplné a pravdivé údaje o projektu nepodléhají ochraně podle zvláštních právních předpisů