(Keynote) New Fabrication Methods and Cathode Designs for Nanofiber Electrode Fuel Cell MEAs

Abstract

When fuel cell electrodes are prepared by a conventional spraying or slot-die coating method, there is little or no control over the multi-scale organization of catalyst particles and polymer binder. Electrode features such as particle and binder interconnectivity, macro-porosity, and micro-porosity are difficult to control, but are critically important when high-performance nanocatalysts are used in fuel cell electrodes. Consequently, the excellent oxygen reduction reaction activity observed in rotating disk experiments with next-generation catalysts does not usually translate into improved hydrogen/air fuel cell performance when such catalysts are incorporated in membrane-electrode-assemblies (MEAs). Nanofiber electrospinning is an electrode fabrication technique that can address fuel cell electrode morphology issues for next-generation MEAs. As a commercial fabrication method, electrospinning is scalable, robust, and cost-effective, especially for the creation of non-woven mats of sub-micron-diameter polymer fibers. In addition to the production of polymer nanofibers, electrospinning can also be used to prepare particle/polymer fiber networks with intra- and inter-fiber porosity. Such fiber mats have been used as the electrode material in Li-ion batteries and H2/air proton-exchange membrane fuel cells [1-4]. In this talk, new experimental results will be presented on nanofiber mat electrode MEAs with Pt/C and Pt-alloy catalysts at cathode loadings of 0.1 and 0.2 mgPt/cm2. Methods for electrospinning fibers with different ionomer binders will be described and new methods of incorporating particle/polymer nanofibers into MEAs will be discussed, with a focus on: (a) developing techniques that can be used with existing roll-to-roll MEA processing lines and (b) varying the electrode morphology at the nano and micron scales. Hydrogen/air fuel cell power output and durability results will be contrasted with data obtained for conventional electrode designs. Acknowledgments This work was funded by the U.S. Department of Energy’s Fuel Cell Consortium for Performance and Durability, DOE-EERE FC-PAD Project DE-EE0007653. References 1. C. Self, M. Naguib, R. E. Ruther, E. C. McRen, R. Wycisk,G. Liu, J. Nanda,and P. N. Pintauro, ChemSusChem, 10, 1823 – 1831 (2017). 2. Brodt, T. Han, N. Dale, E. Niangar, R. Wycisk, and P. Pintauro, J. Electrochem. Soc., 162, F84-F91 (2015). 3. Brodt, R. Wycisk, N. Dale, and P. Pintauro, J. Electrochem. Soc., 163, F401-F410 (2016). 4. J. Slack, C. Gumeci, N. Dale, J. Parrondo, N. Macauley, R. Mukundan, D. Cullen, B. Sneed, K. More, P.N. Pintauro, J. Electrochem. Soc., 166, F3202-F3209 (2019).