1498
Assessment of Nanofiber Electrode MEA Durability By Analytical Electron Microscopy
The unusual but desirable behavior of nanofiber cathodes during a carbon corrosion voltage cycling test warranted further studies, in particular imaging and chemical analysis using scanning transmission electron microscopy (STEM), of cathodes at beginning-of-life (BOL) vs. end-of-life (EOL) (after 1,000 voltage cycles, triangular wave at 1.0 V to 1.5 V at a scan rate of 500 mV/s). Characterization experiments were performed at Oak Ridge National Laboratory using nanofiber MEAs prepared and tested for power output at Vanderbilt University. All MEAs were made with Johnson Matthey HiSpec® 4000 (40% Pt on Vulcan carbon) catalyst at an electrode loading (anode and cathode) of 0.1 mgPt/cm2. The anode binder was always Nafion + poly(acrylic acid) whereas the cathode nanofiber binder was either Nafion + poly(acrylic acid) or Nafion + poly(vinylidene fluoride) (PVDF), where the Nafion/PVDF weight ratio was varied from 80/20 to 20/80. We were particularly interested in understanding how the nanofiber electrode morphology and/or binder composition (e.g., PVDF content and binder hydrophobicity) affected cathode carbon corrosion and power output. In this presentation, results of STEM imaging and compositional analysis of nanofiber MEAs at BOL and EOL will be presented, along with fuel cell polarization curves for the same MEAs.
References
- C. A. Reiser, et al. Electrochemical and Solid State Letters, 8(6): A273-A276 (2005)
- M. Brodt, T. Han, N. Dale, E. Niangar, R. Wycisk, and P. Pintauro, , J. Electrochem. Soc., 162, F84-F91 (2015).
- M. Brodt, R. Wycisk, J. Slack, and P. N. Pintauro, “New Developments in Electrospun Nanofiber Electrodes for Hydrogen/Air Fuel Cells” paper #1250, Electrochemical Society Meeting, Cancun, Mexico (2014).