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Nanofiber electrodes prepared with three different commercial Pt/C catalysts and 1100 EW Nafion® binder were fabricated by electrospinning. The electrodes were further processed into membrane-electrode-assemblies (MEAs) using Nafion 211 as the membrane material. MEAs were evaluated for catalyst activity and power output in a hydrogen/air fuel cell at 80oC. Tanaka Kikinzoku Kogyo (TKK) TEC10E50E (46.1% Pt on Ketjen Black) was more electrochemically active and produced slightly more power than its heat-treated counterpart, TKK TEC10E50E-HT (50.5% Pt on Ketjen Black), and Johnson Matthey HiSpec 4000 catalyst (40% Pt on Vulcan carbon). The nanofiber cathodes were compared to MEAs with standard non-structured gas diffusion electrodes (GDEs) containing the same catalysts, and in all cases, the electrospun fibers generated more power. For example, with a Pt loading of 0.10 mg/cm2, the electrospun TKK TEC10E50E generated 470 mW/cm2 at a 0.65 V vs. 349 mW/cm2 for the GDE-based MEA, an improvement of 35%. The effect of nanofiber composition (the ratio of Pt/C to Nafion) and the effect of fiber diameter on power output were also investigated. In general, such changes had a little or no impact on performance and all the electrospun mats tested yielded MEAs that produced very high power.

A CO2 detection system that enables in-situ and real-time monitoring of CO2 formation from carbon corrosion during start-stop potential cycling was developed. The set-up included a nondispersive infrared (NDIR) CO¬2 detector connected to the fuel cell cathode exhaust. For both Ketjen Black (KB) and Platinum/Ketjen Black (Pt/KB) (50 wt% carbon) cathodes, the amount of CO2 was found to increase with the number of potential cycles (up to 500 cycles) and the carbon loading. Pt was found to increase the initial rate (µg CO2/cycle) of CO2 formation, confirming the findings of earlier studies that Pt accelerates carbon corrosion. Preliminary calculations show that carbon loss is about 30% for both KB and Pt/KB cathodes under the potential cycling protocol used in this study. Pt only acts as a catalyst for the reaction, and it does not significantly affect the total carbon loss which is a function of the amount of corrodible carbon.

An iron based metal-nitrogen-carbon (MNC) type oxygen reduction reaction catalyst was tested for in-situ polarization performance and durability. High open circuit voltage (OCV) of ~0.97 V and high activities were observed. Current density around 750 mA/cm2 was obtained at 0.6 ViR-free/RHE and volumetric current density of 31 A/cm3 was obtained at 0.8 ViR-free. A significant decrease in polarization after start-stop durability test was observed for this catalyst. An attempt was made to recover the in-situ performance after start-stop durability test by running the fuel cell at steady state current density. Partial performance recovery was achieved from the significantly degraded MNC based membrane electrode assembly (MEA). However, performance could not be recovered indefinitely due to eventual carbon loss.

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