Durability Studies on PBI Based High Temperature PEMFC

Abstract

Proton exchange membrane fuel cells (PEMFC) look extremely promising as energy conversion solution for both stationary and transportation applications. However, for the further application, durability still needs to be improved in order to compete with the internal combustion engine.1 The present work focuses on ongoing work based on membrane electrode assemblies (MEAs) for high temperature Proton exchange membrane fuel cells (HT-PEMFCs). HT-PEMFCs were operated at 160-170 °C using either pure humidified hydrogen or humidified reformate of different compositions.2 The high operating temperature makes it possible to operate commercial fuel cell systems using methanol (or methanol-water mixtures) as fuel. The HT-PEM cells can tolerate fuel impurities e.g. up to 3 vol-% CO and 20 ppm H2S without significant performance losses, which could lead to higher operating efficiency.Our studies have shown remarkable durability of an HT-PEMFC equipped with a thermally cross-linked m-PBI membrane. A decay rate of only 0.5 μV /h at 0.2 A/cm2 over an extended period of time (9,200 h) was oserved.3 Further, we have illustrated that an increase in the pressure of the in-going gases to 1.5 bar (abs) – as expected – increases the performance. The preliminary results confirmed a power density of 0.5 W/cm2 at 0.9 A/cm2.Continuous operation and more than 260 start stop cycles have been performed in order to study the degradation effects of both continuous operation and of repeated start stops. The durability of HT-PEMFC can now be considered similar to low temperature PEMFC. Graphs of single cell performance during operation have shown very stable behavior for over 10,000 at a current density of 0.4 A/cm2.Several demonstration projects have been made, especially for cars and we continue improving our products (HT-PEMFCs), looking for innovative solutions to current limitations on HT-PEMFC durability.