Durability of ABPBI‐based MEAs for High Temperature PEMFCs at Different Operating Conditions

Abstract

High temperature PEMFCs based on phosphoric acid‐doped ABPBI membranes have been prepared and characterised. At 160 °C and ambient pressure fuel cell power densities of 300 mW cm–2 (with hydrogen and air as reactants) and 180 mW cm–2 (with simulated diesel reformate/air) have been achieved. The durability of these membrane electrode assemblies (MEAs) in the hydrogen/air mode of operation at different working conditions has been measured electrochemically and has been correlated to the cell resistivity, the phosphoric acid loss rate and the catalyst particle size. Under stationary conditions, a voltage loss of only –25 μV h–1 at a current density of 200 mA cm–2 has been deduced from a 1,000 h test. Under dynamic load changes or during start–stop cycling the degradation rate was significantly higher. Leaching of phosphoric acid from the cell was found to be very small and is not the main reason for the performance loss. Instead an important increase in the catalyst particle size was observed to occur during two long‐term experiments. At high gas flows of hydrogen and air ABPBI‐based MEAs can be operated at temperatures below 100 °C for several hours without a significant irreversible loss of cell performance and with only very little acid leaching.

High temperature proton exchange membranes based on polybenzimidazoles for fuel cells

“…0.2 g m −2 s −1 ) at the cathode but only initially an acid loss (also ca. 0.2 g m −2 s −1 ) at the anode [240,260]. This was confirmed by the nearly constant resistance through the test period of 1000 h, indicating that the acid loss does not seem to be the main reason for the performance degradation.…”

“…With acid-doped AB-PBI, however, Wannek et al [260] reported a high degradation rate of 20-25 V h −1 under constant load. By collecting the acid from the offgas through a water condenser, they observed a constant acid loss (ca.…”

High temperature (HT) polymer electrolyte membrane fuel cells (PEMFC) – A review

“…The main problems reported in the literature are the loss in the catalyst active area due to catalyst agglomeration, and phosphoric acid leaching out from the cell [37,119,120]. It is the opinion of Yu et al [121] and Wannek et al [122] that the main source of performance loss is due to catalyst agglomeration.…”

Exceptional durability enhancement of PA/PBI based polymer electrolyte membrane fuel cells for high temperature operation at 200 °C

“…[14][15][16] In the higher end of the operating temperature regime (180-200 °C) the PA loss rate increases considerably, eventually leading to acid depletion and proton conductivity decay. 6,17 High water activities, i.e. operation at high current loads, further promote this mechanism, 6,18 due to suppressed pyrophosphate formation.…”