PEMFC catalyst layers: The role of micropores and mesopores on water sorption and fuel cell activity

  1. Get@NRC: PEMFC catalyst layers: The role of micropores and mesopores on water sorption and fuel cell activity (Opens in a new window)
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Journal titleACS Applied Materials and Interfaces
Pages18271837; # of pages: 11
SubjectCatalyst layers; Ketjen black; PEM fuel cell; Vulcan XC72; Water retention; Water sorption; Atmospheric humidity; Catalysts; Cathodes; Electrochemical properties; Microporosity; Microstructure; Pore size; Proton exchange membrane fuel cells (PEMFC); Size distribution; Sorption; Water vapor; Water content; carbon; water; article; catalysis; chemistry; electrochemistry; methodology; power supply; Carbon; Catalysis; Electric Power Supplies; Electrochemistry; Water
AbstractThe effects of carbon microstructure and ionomer loading on water vapor sorption and retention in catalyst layers (CLs) of PEM fuel cells are investigated using dynamic vapor sorption. Catalyst layers based on Ketjen Black and Vulcan XC-72 carbon blacks, which possess distinctly different surface areas, pore volumes, and microporosities, are studied. It is found that pores <20 nm diameter facilitate water uptake by capillary condensation in the intermediate range of relative humidities. A broad pore size distribution (PSD) is found to enhance water retention in Ketjen Black-based CLs whereas the narrower mesoporous PSD of Vulcan CLs is shown to have an enhanced water repelling action. Water vapor sorption and retention properties of CLs are correlated to electrochemical properties and fuel cell performance. Water sorption enhances electrochemical properties such as the electrochemically active surface area (ESA), double layer capacitance and proton conductivity, particularly when the ionomer content is very low. The hydrophilic properties of aCL on the anode and the cathode are adjusted by choosing the PSD of carbon and the ionomer content. It is shown that a reduction of ionomer content on either cathode or anode of an MEA does not necessarily have a significant detrimental effect on the MEA performance compared to the standard 30 wt % ionomer MEA. Under operation in air and high relative humidity, a cathode with a narrow pore size distribution and low ionomer content is shown to be beneficial due to its low water retention properties. In dry operating conditions, adequate ionomer content on the cathode is crucial, whereas it can be reduced on the anode without a significant impact on fuel cell performance. © 2011 American Chemical Society.
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AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Fuel Cell Innovation (IFCI-IIPC)
Peer reviewedYes
NPARC number21271395
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Record identifier93bdceee-b198-4edd-84e6-d7534f0236ce
Record created2014-03-24
Record modified2016-05-09
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