Electrospun Nanofiber Electrodes for High and Low Humidity PEMFC Operation

Abstract

MEAs with nanofiber mat electrodes containing Pt/C catalyst and Nafion binder were fabricated and evaluated. The electrodes were prepared by electrospinning a solution of catalyst powder, salt-form Nafion (with Na+, Li+, or Cs+ as the sulfonic acid counterion), and a carrier polymer of either polyethylene oxide or poly(acrylic acid). The carrier polymer was extracted prior to MEA testing by a hot water soaking step. The resulting fibers were 15-17% porous, with a core-shell-like morphology (a coating of primarily Nafion on the fiber surface). MEAs with anode/cathode catalyst loadings of 0.1 mgPt/cm2 each and a Nafion 211 membrane produced high power at both high and low relative humidity (RH) conditions in H2/air fuel cell tests, e.g., a maximum power density of 919 mW/cm2 at 100% RH and 832 mW/cm2 at 40% RH for a test at 80 °C and 200 kPaabs. The presence of nm-size pores within the fibers trapped water via capillary condensation during low RH feed gas testing, thus maintaining a high proton conductivity of the Nafion binder in the anode and cathode while minimizing/eliminating ionic isolation of catalyst particles in low water content, poorly conductive binder.

Enhanced PEMFC performance through high O2 permeation and proton conductive electrospun nanofiber electrodes with unique ionomer construction

“…The reason could be the presence of nmsized pores within the bers by the extraction of PAA carrier polymer-trapped water via capillary condensation, showing a similar voltage trend to PCL electrodes. 30 This suggests that although NFCL has different pore distributions from PCL, the difference in pore distribution did not inuence the cell performance as expected. It demonstrates a weak inuence of the nanober mat pore structure on performance, consistent with the conclusion drawn from LCD results.…”

A Recent Review of Electrospun Porous Carbon Nanofiber Mats for Energy Storage and Generation Applications

“…The ethanolamine (MEA)s with Nafion in salt form (Na+, Li+, or Cs+ as sulfonic acid counterion) were prepared by Waldrop et al They showed little or no change in maximum power density when the relative humidity (RH) of the feed gas was lowered from 100% to 40%, while the eMEAwith H+-Nafion/peroxyacetic acid (PAA) fibers showed a 33% power loss at 40% RH. The higher power densities at low humidity were attributed to capillary condensation of water in porous fibers with a pore diameter of 1.25 nm or less [115]. On the one hand, the interconnected porous structure of nanofibers enables efficient gas diffusion and transport and provides uniform distribution of reactants and products within the fuel cell [110].…”

Electrospun Si and Si/C Fiber Anodes for Li-Ion Batteries

“…Another approach for generating new battery electrode architectures is nanofiber electrospinning. Over the last decade, fiber mat materials, where the fibers contain particles and a polymer binder, have been prepared and characterized for both fuel cell [24,25] and LIB [26][27][28][29] electrodes with promising results. Self et al, for example, showed that a freestanding nanofiber particle/polymer anode containing Si nanoparticles, poly(acrylic acid) and carbon black (Si/PAA/C) worked well in a Li battery coin cell [27].…”