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The Effect of Ionomer to Carbon Ratio and Relative Humidity on Cathode Catalyst Degradation in PEM Fuel Cells

  • The effect of ionomer to carbon (I/C) weight ratio and relative humidity (RH) on cathode catalyst degradation was investigated by comprehensive in situ characterization. Membrane electrode assemblies (MEA) with I/C ratios of 0.5, 0.8 and 1.2 were subjected to an accelerated stress test performed at 40, 70 and 100% RH. The results show an increasing loss in electrochemical active surface area (ECSA) for both higher I/C ratios and RH during voltage cycling. To differentiate between ionomer and water connected ECSA, carbon monoxide stripping measurements were performed at varying RH. Before degradation, all MEAs show comparable total ECSA values, while higher I/C ratios lead to a larger fraction of ionomer connected ECSA. After degradation, ECSA measurements of the lowest I/C ratio showed a relatively higher loss of Pt in contact with ionomer than Pt in contact with water, while an opposite trend was observed for higher I/C ratios. H2 /N2 impedance measurements showed drastically increasing protonic catalyst layer resistances forThe effect of ionomer to carbon (I/C) weight ratio and relative humidity (RH) on cathode catalyst degradation was investigated by comprehensive in situ characterization. Membrane electrode assemblies (MEA) with I/C ratios of 0.5, 0.8 and 1.2 were subjected to an accelerated stress test performed at 40, 70 and 100% RH. The results show an increasing loss in electrochemical active surface area (ECSA) for both higher I/C ratios and RH during voltage cycling. To differentiate between ionomer and water connected ECSA, carbon monoxide stripping measurements were performed at varying RH. Before degradation, all MEAs show comparable total ECSA values, while higher I/C ratios lead to a larger fraction of ionomer connected ECSA. After degradation, ECSA measurements of the lowest I/C ratio showed a relatively higher loss of Pt in contact with ionomer than Pt in contact with water, while an opposite trend was observed for higher I/C ratios. H2 /N2 impedance measurements showed drastically increasing protonic catalyst layer resistances for decreasing RH especially at low I/C ratios, which might hinder Pt 2+ ion diffusion towards the membrane, hence decreasing the ECSA loss. Limiting current measurements show increasing molecular O 2 diffusion resistances at end of test for samples with higher I/C ratios and higher ECSA loss.show moreshow less

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Metadaten
Author:Patrick Schneider, Anne-Christine Scherzer, Brian Storey, Matthias KlingeleGND, Nada Zamel, Dietmar Gerteisen
DOI:https://doi.org/10.1149/1945-7111/acff1f
Identifier:0013-4651 OPAC HS OPAC extern
Identifier:1945-7111 OPAC HS OPAC extern
Parent Title (English):Journal of the Electrochemical Society: JES
Publisher:IOP Publishing Limited
Place of publication:Bristol
Document Type:Article
Language:English
Date of Publication (online):2023/10/16
Year of first Publication:2023
Volume:170.
Issue:10
Article Number:104505
Number of pages:10 Seiten
First Page:1
Last Page:10
Institutes:Fakultät Maschinenbau
IFA – Institut für Innovative Fahrzeugantriebe
Open Access:open_access
Research focus:FSP2: Mobilität
Publication Lists:Klingele, Matthias
Publication reviewed:begutachtet
Licence (German):Creative Commons - CC BY - Namensnennung 4.0 International
Release Date:2024/01/26
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