EFFECT OF IMPURITIES OF A REFORMATE GAS ON PEMFC MEMBRANE ELECTRODE ASSEMBLIES

Proton-exchange membrane fuel cells (PEMFCs) are gaining popularity due to their benefits such as environmental friendliness and increased fuel efficiency. Because of the difficulties inherent to storing hydrogen, fuels such as natural gas, propane, gasoline, diesel are used to produce reformate gas. Dry reformate obtained by steam reforming is tipically composed of 65-70% hydrogen, 20-25% carbon dioxide, about 5% nitrogen, and several impurities: hydrocarbons (~1%), carbon monoxide (<50 ppmV), sulphur (<10 ppmV).
It is well known that CO poisons the platinum catalysts used in PEMFC system, indeed several efforts are devoted to develop CO tolerant anode catalysts; whereas less information are available on sulphur and hydrocarbons effects on MEA (Membrane Electrolyte Assembly). In this work the effects of CO, methane and H₂S on the electrochemical performance of MEAs are studied.
Simulate reformate gas was fed to the anode side by adding increasing amount of CO (from 50 to 750 ppmV), of CH₄ (from 1 to 2.8%) and of H₂S (from 5 to 45 ppmV). A higher level of impurities than that of a typical reformate composition was reached in order to accelerate the poisoning effects.
The MEAs, furnished by Arcotronics Fuel Cell were tested, after conditioning, keeping constant the current density at 0.3 A/cm². The poisoning effect was evaluated considering the voltage decrease during the tests.
Different percentages of air bleeding were employed in presence of different amounts of CO and the recovery in pure hydrogen was considered.