Fuel cell and gas diffusion electrode used for fuel cell

Abstract

Disclosed is a fuel cell comprising a pair of catalyst layers so arranged as to sandwich a proton conductive electrolyte membrane therebetween. The fuel cell is characterized in that at least a catalyst layer of the cathode is composed of a mixture including a catalyst component, an electrolyte material and a carbon material which is composed of a catalyst supporting carbon material carrying the catalyst component and a gas diffusion carbon material not carrying the catalyst component, and the water vapor adsorption of the catalyst supporting carbon material at a relative humidity of 90% at 25 1 / 2 C is not less than 50 ml / g.

Description

technical field [0001] The present invention relates to a fuel cell, and more particularly, to an electrode with excellent output characteristics that improves the movement of substances in a catalyst layer and reduces costs by increasing the effective utilization of catalyst components, and a fuel cell using the electrode. Background technique [0002] If we take the structure of an ordinary solid polymer fuel cell as an example, its electrode structure has the following basic structure: one catalyst layer becomes the cathode, and the other becomes the anode, and the catalyst layer is joined together with the polymer electrolyte membrane sandwiched between them. Both sides are connected with waterproof treated carbon paper as gas diffusion layer. [0003] In order to extract current from a fuel cell with such a basic structure, an oxidizing gas such as oxygen or air is supplied from the outside through a gas diffusion layer to the cathode side, and a reducing gas such as hy...

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Problems solved by technology

That is, in U.S. Patent No. 5,620,807 specification, although the preferred ranges of porosity and pore diameter are specified, the carbon particles or fibers used are not specified, especially the method of controlling the pore diameter of the microporous layer in contact with the catalyst layer. Depending on the amount and molecular weight of the polymer material that is one of the main components, it is difficult to control the pore diameter and cannot be generalized

[0051] In addition, in Japanese Patent Laid-Open No. 10-261421, a laminated structure involving a gas diffusion layer with a two-layer structure is proposed, and the same as the specification of U.S. Patent No. 5,620,807, there is no provision for the type or structure of the preferred carbon black, only based on It is difficult to derive all catalyst layer properties from the proposed

[0052] In particular, in the aforementioned U.S. Patent No. 5,620,807 specification or Japanese Patent Laid-Open No. 10-261421, the methods for securing the gas diffusion path are both based on waterproof polymer materials, and in order to improve the gas diffusivity, it is necessary to improve the insulation. The content of non-conductive polymer materials, which tends to impair the electrical conductivity

[0053] In addition, in Japanese Patent Laid-Open No. 2001-57215, it is proposed to mix large-diameter carbon particles and small-diameter carbon particles as the main component of the gas diffusion layer in contact with the catalyst layer. Although the structure of the carbon material itself is mentioned, However, depending on the combination of particle sizes, the gas diffusion path may be blocked instead. When using the pores formed in the gaps between different kinds of large-diameter carbon particles and small-diameter carbon particles as the gas diffusion path, there may be some problems due to the connection pressure of the battery. However, it is not a satisfactory proposal if the particles are moved to block the pores, or the arrangement of the particles is changed due to long-term use, and the pore diameter changes from the most suitable state.

[0054] Therefore, based on what has been proposed in the past, it is difficult to derive the maximum performance of the catalyst layer even though a certain degree of performance can be exhibited when the catalyst layer having high performance is connected to the gas diffusion layer.

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