Experimental Characterization of the Poisoning Effects of Methanol-Based Reformate Impurities on a PBI-Based High Temperature PEM Fuel Cell

Abstract

In this work the effects of reformate gas impurities on a H₃PO₄-doped polybenzimidazole (PBI) membrane-based high temperature proton exchange membrane fuel cell (HT-PEMFC) are studied. A unit cell assembly with a BASF Celtec^®-P2100 high temperature membrane electrode assembly (MEA) of 45 cm² active surface area is investigated by means of impedance spectroscopy. The concentrations in the anode feed gas of all impurities, unconverted methanol-water vapor mixture, CO and CO₂ were varied along with current density according to a multilevel factorial design of experiments. Results show that all the impurities degrade the performance, with CO being the most degrading agent and CO₂ the least. The factorial analysis shows that there is interdependence among the effects of the different factors considered. This interdependence suggests, for example, that tolerances to concentrations of CO above 2% may be compromised by the presence in the anode feed of CO₂. Methanol has a poisoning effect on the fuel cell at all the tested feed ratios, and the performance drop is found to be proportional to the amount of methanol in feed gas. The effects are more pronounced when other impurities are also present in the feed gas, especially at higher methanol concentrations.