However, in current state-of-the-art fuel cells, each unit volume of electrode contains a random mix of components that must simultaneously provide catalytic activity, water transport, O2transport, electronic conductivity, and protonic conductivity. Since each unit must provide all functions, units cannot be optimized for individual functions. By separating the different electrode functions into discrete electrode elements, each element can be optimized for specific functions as shown in Figure 1a. Arranging these optimized discrete elements in a controlled, low-tortuosity configuration enables transport limitations to be reduced or eliminated. In previous work, Middlemen et al. showed under optimal conditions oriented catalyst layer structure can be fabricated but didn’t present any electrochemical evaluation 3. Komini Babu et al. fabricated vertically oriented Nafion nanofibers and deposited Pt via vapor deposition 4. The Nafion nanofiber electrode showed increase in performance compared to Pt sputtered on Nafion 115 electrode but lower in performance to Pt/C based electrode.
In this work, we propose an alternate electrode structure to enable good transport behavior and high cell performance through controlled deposition of electrode components in an optimized, organized structural configuration. Figure 1b shows the SEM image of Nafion nanofibers for proton transport, fabricated by solution casting on a porous template. Providing effective proton transport through these low-tortuosity percolating highways allows the catalyst domain to have a lower ionomer/catalyst ratio, reducing transport resistance.
This research is supported by DOE Fuel Cell Technologies Office, through the Fuel Cell Performance and Durability (FC-PAD) Consortium; Fuel Cells program manager: Dimitrios Papageorgopoulos.
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3. E. Middelman, Fuel Cells Bull., 2002, 9–12 (2002).