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Author:Jokimies, Sonja
Title:Studies on Polymer Electrolyte Membrane Fuel Cell Degradation
Polymeeripolttokennojen degradaatio
Publication type:Master's thesis
Publication year:2008
Pages:47      Language:   eng
Department/School:Teknillisen fysiikan laitos
Main subject:Ydin- ja energiatekniikka   (Tfy-56)
Supervisor:Lund, Peter
Instructor:Mikkola, Mikko
OEVS:
Electronic archive copy is available via Aalto Thesis Database.
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Location:P1 Ark TF80     | Archive
Keywords:fuel cell
PEMFC
degradation
FER
polttokenno
PEMFC
degradaatio
fluoridiemissio
Abstract (eng):A Polymer Electrolyte Membrane Fuel Cell (PEMFC) is an electrochemical energy conversion device suitable for lowtemperature applications with high energy density.
One of the largest obstacles in commercializing fuel cells is their short life time.
In this thesis a literature survey of the PEM fuel cell degradation mechanisms is made.
The most severe damage is encountered by the membrane and the electrodes.
In the experimental part of this thesis a so called multisinglecell, which consists of electrically connected cells with individual gas connections, was used.
A long term open circuit voltage hold test and a constant current hold test were conducted.
Outlet water from cells was collected and analyzed for fluoride ions, which is the main decomposition product in membrane degradation.
In the OCV test the fluoride emission rates were in practice similar at the anode and the cathode, and after 288 h they increased markedly.
FERs from the constant current cells were smaller because OCV operation enhances membrane degradation.
After the experiments the MEAs were analyzed with a transmission electron microscope.
The images showed that the sample preparation method was unsuitable and damaged the membrane, so that no results for structure changes were obtained
Abstract (fin):Polymeeripolttokenno on sähkökemiallinen energianmuuntolaite, joka sopii matalan lämpötilan sovelluksiin korkealla energiatiheydellä.
Suurimpia esteitä polttokennojen kaupallistumiseen on niiden lyhyt elinikä.
Tässä työssä tehtiin kirjallisuusselvitys polymeeripolttokennojen degradaatiomekanismeista.
Pahimmat vauriot aiheutuvat membraanille ja elektrodeille.
Tämän työn kokeellisessa osassa käytettiin ns. moniyksikkökennoa, joka koostuu sähköisesti kytketyistä kennoista, joilla on omat erilliset kaasuliitännät.
Pitkäkestoinen avoimen piirin koe sekä vakiovirtamittaus suoritettiin.
Kennojen ulostuloista kerättiin vesi talteen ja siitä analysoitiin fluoridi-ionipitoisuus, sillä fluoridi on membraanien degradaation päähajoamistuote.
Avoimen piirin kokeessa fluoridiemissionopeudet olivat käytännössä samat anodilla ja katodilla ja 288 tunnin jälkeen ne nousivat merkittävästi.
Fluoridiemissionopeudet vakiovirtamittauksessa olivat pienempiä, sillä avoimen piirin tila kiihdyttää membraanin hajoamista.
Mittausten jälkeen membraanin ja elektrodit sisältävä kalvo analysoitiin läpäisyelektronimikroskoopilla.
Kävi ilmi, että näytteiden valmistusmenetelmä ei soveltunut tälle materiaalille ja vahingoitti membraania.
Näin ollen rakennemuutoksia ei voitu havaita.
ED:2009-02-17
INSSI record number: 36753
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