Phase Change Driven Water Transport in Polymer Electrolyte Fuel Cells

摘要

The objective of this work is to investigate water transport of polymer electrolyte fuel cell (PEFC) materials subjected to a temperature gradient. Experiments on different fuel cell materials (Nafion~®, reinforced membrane, reinforced membrane electrode assembly (MEA), non-reinforced MEA, hydrophilic and hydrophobic diffusion media) were performed using an in-house fuel cell fixture with an imposed temperature gradient between the anode and cathode.rnContrary to thermo-osmotic flow in fuel cell membranes (17, 18), a net flux of water was found to flow from the hot to cold side of the fuel cell. The key to this is the existence of some gas phase in the catalyst layer or other porous media. This mode of transport can be explained by a phase-change driven flow, also known as a heat pipe effect. The measured water transport through the membrane electrode assembly is the net effect of mass diffusion as well as thermo-osmosis in the membrane, which moves counter to the direction of the phase-change driven flow. The net flux of water was fit by Arrhenius functions that are dependent on material set, temperature gradient, and average temperature across the materials. In addition to direct quantification, the phase-change driven flow was visualized and confirmed using high resolution neutron radiography.