| 초록 |
Proton exchange membrane fuel cell (PEMFC) engines can potentially replace the internal combustion engine for transportation because they are clean, quiet, energy efficient, modular, and capable of quick start-up. Since a PEMFC simultaneously involves electrochemical reactions, current distribution, hydrodynamics, multicomponent transport, and heat transfer, a comprehensive mathematical model is needed to gain a fundamental understanding of the interacting electrochemical and transport phenomena and to provide a computer-aided tool for design and optimization of future fuel cell engines.The diffusion layer in a PEMFC consists of a thin layer of carbon black mixed with polytetrafluoroethylene (PTFE) that is coated onto a sheet of macro-porous carbon backing cloth. This diffusion layer provides a physical micro-porous support for the catalyst layer while allowing gas transport to and from the catalyst layer. Although the diffusion layer is a seemingly minor component in a fuel cell, it has been shown that altering the composition of the diffusion layer can lead to substantial improvements in the performance of the cell. The improvements reported relate to the thickness of the layer, and the porosity of the layer.The diffusion layer was prepared by screen-printing that could make it very thin. The effect of diffusion layer thickness was attributed to a decrease in the electrical resistance of the gas diffusion electrode as the diffusion layer thickness was increased. A thinner diffusion layer will improve gas diffusion properties by providing a shorter path for gas diffusion. However, if the diffusion layer is made too thin, some other factors become pertinent. The reason for lower cell performances at low diffusion layer loadings is high electronic resistance in the electrode, since the electronic contact area between the catalyst and diffusion layers is thought to become too small at low diffusion layer loadings.The goals of this work are to find the optimum thickness of the gas diffusion layer and analyze the variables related to the electrode by simulation. |
