Kyoung-hwan Choi

Water transport in polymer membranes for PEMFC

To determine the net electro-osmotic drag coefficient of Nafion 115 and Hanwha membrane, we measured the fluxes of water discharged from anode and cathode at different current densities. Also, we investigated the contribution of water supply for membrane from anode and cathode. When the cathode was humidified, water supply for membrane at low current densities was achieved via the cathode, but the contribution of the anode became more important as current density gradually increased. The net electro-osmotic drag coefficient decreased sharply with current density, but it had a nearly constant value over 200 mA cm−2. When the cathode was not humidified, at low current densities, most of water generated at cathode was supplied for membrane, but water supply from cathode at high current densities decreased proportionately, and the net electro-osmotic drag coefficient showed larger value.

Real-time, In situ Measurement of Fuel and Crossover Methanol Vapor Concentration of a Vapor-Fed Passive Direct Methanol Fuel Cell Using Laser Absorption Spectroscopy

The concentration of methanol vapor in a vapor-fed direct methanol fuel cell (DMFC) is measured using absorption spectroscopy with a 3.39 µm He–Ne laser. A noise correction method is applied to compensate for the higher noise levels associated with the He–Ne laser. Based on this, real-time, in situ measurement of the methanol vapor concentration has been performed simultaneously in a methanol vapor transport layer and on the cathode surface (air transport layer) under various DMFC operating conditions. The change in methanol vapor concentration and cell performance is measured at various galvanostatic conditions and the impact of methanol concentration in the methanol transport layer on the methanol crossover amount is analyzed. Moreover, the changes of methanol vapor concentration are measured when the fuel supply is suspended during fuel cell operation. No previous method has been able to measure the concentration of the methanol vapor in the methanol transport layer and the air transport layer in real-time with noncontact. The results from this study can contribute to the development of stable and high-power vapor-fed DMFCs.