New Developments in Electrospun Nanofiber Electrodes for Hydrogen/Air Fuel Cells
Previously, we have shown that more power was generated from nanofiber electrode MEAs than a conventional MEA with decal electrodes [1,2]. For example, the maximum power density for a H2/air fuel cell with a nanofiber cathode and anode (at loadings of 0.065 mgPt/cm2 and 0.10 mgPt/cm2, respectively) was 437 mW/cm2 vs. 400 mW/cm2 for a decal MEA with a cathode containing 40% more Pt (a loading of 0.104 mgPt/cm2) and an anode loading of 0.10 mg/cm2. In these experiments, the nanofiber catalyst binder was a mixture of Nafion® and poly(acrylic acid), the binder used in decal electrodes was neat Nafion, and the membrane was Nafion 212. The fuel cell operating conditions were: 80oC, 1 atm (ambient) pressure, 125 sccm H2, and 500 sccm air. As another example, an electrospun cathode with a Pt loading of 0.055 mg/cm2 produced a maximum power density of 906 mW/cm2 at 80°C and 3 atm pressure with 2000 sccm fully humidified air and 500 sccm H2. Additionally, the mass activity (0.16 A/mgPt at 0.9 V) and electrochemical surface area (~41 m2/g) of nanofiber cathodes containing Johnson-Matthey HiSpec™ 4000 catalyst were found to be very high and electrospun cathodes exhibited less degradation than a conventional decal cathode in an accelerated voltage cycling durability test.
In this presentation, new catalyst/binder electrode formulations will be discussed, in terms of the conditions required to electrospin well-formed fibers and the performance of the fiber mats as cathodes in a hydrogen/air fuel cell operating at 80oC. MEAs are assessed in terms of the initial power density at high and low humidity operation and the changes in power output during voltage cycling Pt dissolution and carbon corrosion durability experiments. All anode and cathodes were prepared with Johnson Matthey HiSpec 4000 catalyst (40% Pt on Vulcan carbon), at a Pt loading of 0.10 mg/cm2.
This work was funded by EMD Millipore and the NSF-funded TN-SCORE program, NSF EPS-1004083, under Thrust 2.
- W. Zhang and P. N. Pintauro, ChemSusChem, 4, 1753-1757 (2011).
- M. Brodt, R. Wycisk, and P. N. Pintauro, Journal of the Electrochemical Society, 160, F744-F749 (2013).