| 摘要 |
A porous supporting carbon body of a gas diffusion layer is provided with a larger number of smaller pores at its catalyst layer side and a smaller number of larger pores at the other side, particularly with an appropriate distribution of finer mesh at its catalyst layer side and coarser mesh at the other side. Thereby, a high performance polymer electrolyte fuel cell can be obtained in which water generated at the catalyst layer is quickly sucked out to the gas diffusion layer, and is evaporated at the gas diffusion layer to be effectively exhausted to outside the fuel cell, so that excessive water can be prevented from retaining in the gas diffusion electrode, with the polymer electrolyte membrane being maintained at an appropriately wet condition. Further, a gas diffusion layer is provided with an electrically conductive polymer-containing layer comprising carbon particles and a polymer material. In it, a combination of two kinds of carbon particles having different amounts of acidic function group is used in a manner that the weight ratio of one kind having a larger acidic function group, relative to the other kind, increases from one end of the gas diffusion layer, corresponding to the inlet of a gas flow channel, to the other end. Thereby, the water permeating function at the surface of the gas diffusion layer can be so adjusted that the inside of the MEA is maintained at an appropriately wet condition, while excessive water is quickly exhausted to outside of the fuel cell together with e.g. the reactive gas. This can also be achieved by using a combination of two kinds of polymer materials in the electrically conductive polymer-containing layer in a manner that the two kinds have either different degrees of crystallinity or different coefficients of moisture permeability, so that the degrees of crystallinity decreases and the coefficients of moisture permeability increases from the one end to the other end of the gas diffusion layer. |
