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PEMFC Catalyst Layers: The Role of Micropores and Mesopores on Water Sorption and Fuel Cell Activity Tatyana Soboleva,†,‡ Kourosh Malek,‡ Zhong Xie,‡ Titichai Navessin,‡ and Steven Holdcroft†,‡,* † ‡
Department of Chemistry, Simon Fraser University, 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6 Institute for Fuel Cell Innovation, National Research Council Canada, 4250 Wesbrook Mall Vancouver, British Columbia, Canada V6T 1W5 ABSTRACT: The 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.6 This has several implications for the design of catalyst layers. First, only the surface area of pores larger than ∼20 nm is available for distributing the ionomer; hence, an increase in carbon surface area through introduction of microporosity, as in Ketjen Black, might not result in the efficient distribution of ionomer. An optimal quantity of ionomer in the CL is highly specific to the mesoporous surface area of the carbon and thus 30 wt % ionomer cannot be optimal for carbons that differ in mesoporous surface area. Received: November 7, 2010 Accepted: May 16, 2011 Published: May 16, 2011 1827
dx.doi.org/10.1021/am200590w | ACS Appl. Mater. Interfaces 2011, 3, 1827–1837
ACS Applied Materials & Interfaces Second, Pt particles deposited in the pores
