Journal of Power Sources 196 (2011) 179–181 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Short communication Fuel cell catalyst layers containing short-side-chain perfluorosulfonic acid ionomers Jennifer Peron a , Dave Edwards a , Mark Haldane a , Xiaoyan Luo b , Yongming Zhang c , Steven Holdcroft a,b,∗∗ , Zhiqing Shi a,∗ a Institute for Fuel Cell Innovation, National Research Council Canada, Vancouver, British Columbia, Canada V6T 1W5 b Department of Chemistry, Simon Fraser University, Burnaby, British Columbia, Canada V5A 1S6 c School of Chemistry and Chemical Technology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai 200240, China article info Article history: Received 26 April 2010 Received in revised form 15 June 2010 Accepted 16 June 2010 Available online 23 June 2010 Keywords: Short-side-chain PFSA ionomer PEMFC Catalyst layers Low equivalent weight Fuel cells PEM abstract Porous catalyst layers (CLs) containing short-side-chain (SSC) perfluorosulfonic acid (PFSA) ionomers of different ion exchange capacity (IEC: 1.3, 1.4 and 1.5 meq g -1 ) were deposited onto Nafion 211 to form catalyst-coated membranes. The porosity of SSC-PFSA-based CLs is larger than Nafion-CL analogues. CLs incorporating SSC ionomer extend the current density of fuel cell polarization curves at elevated temperature and lower relative humidity compared to those based on long-side chain PFSA (e.g., Nafion)- based CLs. Fuel cell polarization performance was greatly improved at 110 ◦ C and 30% relative humidity (RH) when SSC PFSI was incorporated into the catalyst layer. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. 1. Introduction Perfluorosulfonic acid (PFSA) ionomers are commonly employed in PEMFCs catalyst layers (CLs) to ensure proton transport between the PEM and reaction sites in the CL [1,2]. Current PEMFCs utilize long-side-chain (LSC) PFSA ionomer, e.g. Nafion, and much has been reported on the structure–properties relationships of LSC-PFSA-based CLs [3]. During CL fabrication, carbon-supported Pt and ionomer segregates on various length scales into bicontinuous percolating phases, the optimal Nafion content being ∼30–35 wt% [4–8]. For automotive applications it is preferable that PEMFCs operate at temperatures >100 ◦ C and low RH but LSC-PFSA ionomer loses proton conductivity above 90 ◦ C and under lower RH [9]. Attention is thus being paid to short- side-chain (SSC) PFSA ionomers, as they possess longer sequence lengths between side chains (for a given IEC) that translate to a higher degree of crystallinity and higher thermal transition temperatures than LSC analogues [10,11]. Moreover, the enhanced ∗ Corresponding author at: 4250 Wesbrook Mall, Vancouver, British Columbia, Canada V6T 1W5. Tel.: +1 604 221 3000; fax: +1 604 221 3001. ∗∗ Corresponding author at: 8888 University Drive, Burnaby, British Columbia, Canada V5A 1S6. Tel.: +1 778 782 4221; fax: +1 778 782 3785. E-mail addresses: holdcrof@sfu.ca (S. Holdcroft), ken.shi@nrc-cnrc.gc.ca (Z. Shi). crystallinity enables the preparation of higher IEC PFSA ionomers that do not dissolve or become too gelatinous upon exposure to water. SSC-PFSA ionomer was developed by Dow Chemicals in the mid-1980s, however, due to the complexity and cost of synthesis of the functional monomer further development was abandoned [12]. A simpler route for the synthesis of SSC ionomer was developed and marketed under the trade name Aquivion ® (previously Hyflon ® ) by Solvay Solexis [12]. SSC-PFSA ionomer membranes (PEMs) have been previously characterised ex situ and in fuel cells [10,13–15], as have theoretical studies aiming to explain the morphology of SSC-PFSA as a function of IEC [16,17]. The development of new ionomers to replace Nafion as a mem- brane has led to the incorporation of new ionomers in the catalyst layer. The influence of parameters such as ion exchange capacity and ionomer content of the catalyst layer has been previously reported for LSC-PFSA [8,18,19] and for several non-perfluorinated polymers, examples of which include sulfonated polyetherketones [20–24], polyimides [25], polybenzimidazoles [26], sulfonated polysulfones and polyethersulfones [27–29]. However, despite the importance of the ionomer in the CL [1,2], reports on the incorporation of SSC-PFSA, and the effect of incor- porating high IEC ionomer, are absent. In this work the influence of SSC-PFSA, and IEC, on fuel cell CL performance is reported and compared to Nafion ionomer. The IECs of SSC-PFSA studied were 1.3, 1.4, and 1.5 meq g -1 , i.e. much higher than that of Nafion 0378-7753/$ – see front matter. Crown Copyright © 2010 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2010.06.050