am201360j_si_001.pdf (45.02 kB)
Preparation and Fuel Cell Performance of Catalyst Layers Using Sulfonated Polyimide Ionomers
journal contribution
posted on 2012-02-22, 00:00 authored by Takuya Omata, Manabu Tanaka, Kenji Miyatake, Makoto Uchida, Hiroyuki Uchida, Masahiro WatanabeSulfonated polyimide (SPI-8) ionomers were used as binders
in the
catalyst layers, and their fuel cell performance was evaluated. SPI-8
ionomers functioned well in the anode with only minor overpotential
even at low humidity (50% relative humidity (RH)). In contrast, the
cathode performance was significantly dependent on the content and
molecular weight of the ionomers and humidity of the supplied gases.
Higher molecular weight of the ionomer caused larger potential drop
at high current density at 80 and 100% RH since oxygen supply and/or
water discharge became insufficient due to higher water uptake (swelling)
of the ionomer. Similar results were obtained at higher ionomer content,
because of the increase of thickness in the catalyst layer. The mass
transport was improved with decreasing humidity, however, proton conductivity
became lower. While the maximum values of j@0.70 V for all membrane electrode assemblies (MEAs) were ca. 0.35 A/cm2, each electrode could have the different appropriate operating
conditions. The results suggest that the parameters such as oxygen
supply, proton conductivity, and water uptake and discharge need to
be carefully optimized in the catalyst layers for achieving reasonable
cathode performance with hydrocarbon ionomers.