Experimental and modeling studies of direct methanol fuel cells

The performance of the direct methanol fuel cell (DMFC) and the various transport mechanisms have been studied both experimentally and mathematically.; A. A specially designed fuel cell fixture was used to study the effect of the gas diffusion layer (GDL) compression and the component tolerance on the performance of PEM fuel cells (PEMFCs) and DMFCs. The results show that both the GDL compression and the component tolerance have significant effect on the cell performance.; B. The effects of operating parameters on the performance of the DMFC have been systematically studied. The operating parameters include the cell temperature, the methanol concentration, the cathode humidification temperature and both the anode and cathode flow rates.; C. A new set of experiments is designed to study the effect of methanol cross-over on the performance due to the methanol oxidation in the cathode catalyst layer. The experimental results show that the thickness of cathode catalyst layer indeed has significant effect.; D. A one-dimensional model was developed to study the effect of methanol oxidation and methanol cross-over on the performance. Not only the mixed over-potential was considered, but also the role of methanol concentration in the cathode catalyst layer was also investigated which was ignored in almost all other models.; E. A three-dimensional, single-phase and multi-component model has been developed for a liquid-fed DMFC. The traditional continuity, momentum, and species conservation equations are used. The modeling results compared well with our experimental data.; F. A 3D multi-component and two-phase model has been developed for a liquid-fed DMFC. Two phases (liquid and gas) are considered in the entire anode; while at the cathode, two-phases are considered in the gas diffusion layer and the catalyst layer but only single gas phase is considered in the channel. The modeling results also show that the single-phase flow models over-predict methanol cross-over.