The effect of ammonia as an anode impurity on the performance of PEM fuel cells.

摘要

The effects of ammonia as fuel impurity on the performance of Proton Exchange Membrane Fuel Cells (PEMFCs) have not been widely tested in-situ and therefore this dissertation focus on these effects. Ammonia is chosen not only because it is an impurity resulting from reforming nitrogen containing hydrocarbons but because it can serve as a model for impurities that appear to attach the ionomer rather than the catalyst. This is of importance to the developers of Membrane Electrode Assemblies (MEAs) and filters and it will provide an understanding of the mechanism of the MEA poisoning with these impurities. Data are presented to provide insight on the extent of NH 3 effects at different concentration levels for high performance MEAs as well as to provide a basis for the poisoning mechanism when NH3 is introduced to the anode side of a PEMFC. Data are also shown for NH3 present on a reformate mixture. Reformate contains N 2, CO2, and H2.; In addition to the commercially available MEAs, electrodes were prepared with ETEK type gas diffusion media with 15%, 20%, and 25% Nafion in the catalyst. These electrodes were studied at 200 ppm NH3 in neat H2 by recording changes in the cell voltage corresponding to a step change from neat H2 to the NH3/H2 mixture while the current density was 0.6 A/cm2. A model is presented to help understand which of these mechanisms is controlling the performance of the cell.