The PEMFC electrode is a porous gas diffusion electrode, generally composed of a gas diffusion layer and a catalyst layer. High-performance carbon fiber paper is a gas diffusion layer material widely used in electrodes. At present, PEMFC research units in China basically use carbon fiber paper from Japan’s TORAY company, German technology company (SGL) or Canada’s SGL Ballard company. Therefore, the development of high-performance carbon fiber paper with independent intellectual property rights has important theoretical and practical significance.
The gas diffusion electrode is the core component of PEMFC, and the gas diffusion layer is an important component of the electrode. Commonly used gas diffusion layer materials include carbon fiber paper, carbon fiber woven fabric, non-woven fabric and carbon black paper. But some also use metal materials, such as flat metal sponge-mesh metal nickel. Among them, carbon fiber paper is a gas diffusion layer material widely used in electrodes. PEMFC must meet the following performance requirements:
⑴ Uniform porous structure gives it excellent air permeability;
⑵ Low resistivity gives it high electronic conductivity;
⑶ The structure is compact and the surface is flat, reducing contact resistance and improving electrical conductivity;
⑷ It has certain mechanical strength, which is conducive to the production of electrodes and provides stability of the electrode structure under long-term operating conditions;
⑸ It has chemical stability and thermal stability;
⑹ Low manufacturing cost, high cost performance.
Carbon fiber paper patent
At present, Japan Toray Company has applied for many carbon fiber paper patents, and it has been continuously improved in recent years. US2005100498 is a US patent filed by Japan’s MITSUBISHI RAYON in 2003. Its carbon fiber paper uses organic polymer compounds as a binder. It selects carbon fibers with an average diameter of less than 5 μm and an average length of 3 to 10 mm, and introduces the use of this carbon fiber paper for making Manufacturing method of porous carbon electrode material.
JP2003323897, which was filed in 2002, introduced an electrode material and carbon paper material with high conductivity and flexibility. The carbon paper includes carbon fibers and acid groups instead of water-soluble aniline conductor polymers, and the polymers are also substituted with sulfur or carboxyl groups.
Among Chinese patents, many foreign (especially Japanese) companies have applied for patents, while Chinese companies have applied for fewer patents. For example, the Chinese patent filed by Shanghai Yiji Technology Co., Ltd. on November 9, 2001 provides a carbon fiber paper material (CN1417879) for the gas diffusion layer of fuel cell electrodes. The carbon fiber paper material of the present invention uses short-height carbon fibers as the raw material for papermaking slurry, and is characterized in that the length of the short-height carbon fibers is distributed between 0.5 mm and 5.0 mm, and the average length is between 1.0 mm and 3.0 mm. It accounts for 96% to 99% by weight. Since the carbon fiber paper material contains short-height carbon fibers of different lengths, these short fibers of different lengths are overlapped and entangled with each other to form an excellent conductive system, and have uniformly distributed pores, ensuring uniform gas diffusion and overcoming traditional electrodes. The carbon paper of the gas diffusion layer has shortcomings in terms of resistivity, porosity and uniformity. The invention patent was authorized and announced in January 2005.
In November 2002, Beijing University of Petroleum disclosed a functional carbon paper with different hydrophilic and hydrophobic properties on both sides and its preparation technology. Because the two sides of carbon paper have different hydrophilic and hydrophobic properties, this process avoids the complicated post-treatment process when using carbon paper. At the same time, by adding graphite powder and other substances in the preparation process, the carbon paper has good conductivity and suitable porosity (CN1378014).
Carbon fiber paper products
The most famous international brands are the products of German Technology Company (SGL), Japan's TORAY Company and Canada's Ballard Material Products Company.
German SGL company uses high-quality carbon fiber as raw material to produce various textile products, such as SIGRATEX non-woven fabrics. It chooses PAN-based carbon fiber, and it can be produced through a very common production process. It has flexibility and good conductivity, and there is no health hazard. In addition, it also has the characteristics of anti-acidification, smooth surface, and avoiding the electrostatic load of semiconductors, which is suitable for the electrode substrate of electrochemical cells.
TORAY is another famous carbon paper production company. It was established in 1971, mainly engaged in the human-type industrial production of PAN-based carbon fiber, and named its product "TORAYCA", which is the abbreviation of TORAY carbon fiber. Currently, TORAY is a global leader in the production and marketing of carbon fiber. The carbon fiber paper produced by Toray has many advantages such as high conductivity, high strength, high gas permeability, and smooth surface.