Future Development Direction of Fuel Cell CCM Membrane Electrode Assemblies
CCM membrane electrodes in fuel cells mainly include proton exchange membranes, catalysts, gas diffusion layers (GDLs) (prepared by CCM), and sometimes GDLs are not classified as CCM membrane electrodes according to catalyst loading. This paper mainly summarizes the research and development progress of each CCM membrane electrode assembly and the research units at home and abroad. In addition to hydrogen, hydrogen storage, transportation and hydrogenation, the upstream technologies of the hydrogen fuel cell industry chain also include the core materials and components of fuel cells such as electrolyte membranes, catalysts, anode plates, gas diffusion layers, air compressors, pumps, and hydrogen pumps.
1. Proton exchange membrane
The proton exchange membrane is the core element and core material of the fuel cell. During the reaction, the anode allows hydrogen ions (protons) that have lost electrons to reach the cathode, but prevents the passage of electrons, hydrogen molecules, water molecules, etc., so the following characteristics are required: (1) High conductivity (highly selective ionic conduction, not electronic conduction) ) (2) Good chemical stability (acid resistance and redox resistance). (3) Good thermal stability. (4) Mechanical properties of CCM membrane electrodes (such as strength and flexibility); (5) Low gas permeability of reactive gases and small electroosmotic coefficient of water. (6) Good workability and reasonable price.
Proton exchange membrane mechanism of action
The proton exchange membrane is the core component of the proton exchange membrane fuel cell (PEMFC). The CCM membrane electrode is mainly a perfluorosulfonic acid membrane. At present, the process of localization is accelerating. The perfluorosulfonic acid membrane has mechanical strength, chemical stability and high humidity. It has the advantages of high conductivity under the same conditions, but the disadvantages are high temperature, poor proton conductivity, easy chemical decomposition at high temperature, and difficulty in monomer synthesis. The current mainstream trend of proton exchange membranes is perfluorosulfonic acid reinforced composite membranes. The proton exchange membrane is gradually thinned, from tens of microns to 10 microns, reducing the ohmic polarization of proton transfer and enabling higher performance. The development of CCM-type thin catalytic layer electrodes with low platinum and high reaction efficiency is an important technical direction for the development of proton exchange membrane fuel cells.
Metal catalyst-PT/C is the current mainstream, and ultra-low platinum and no tungsten are the future directions. CCM membrane electrode metal catalyst is one of the materials of hydrogen fuel cells. The metal catalyst acts on hydrogen and makes electronic devices leave hydrogen atoms. The most commonly used commercial metal catalyst in current hydrogen fuel cells is Pt/C, which is composed of nano-Pt particles (3–5 nm) and a large-surface-area activated carbon package of Pt particles such as pillars. One of the primary problems in the commercialization of ion-exchange membrane hydrogen fuel cells is the heavy metal catalyst, the plutonium load is greatly reduced, and the ultra-low plutonium or plutonium-free is the core of future scientific research. The cost of fuel cell components mainly comes from raw material and processing costs. A report published by Strategic Analysis in the United States pointed out that at the current level of technology, the cost of proton exchange membranes, gas diffusion layers and other processing cost components can be reduced through large-scale production, but the material cost of catalysts is difficult to reduce through mass production. cost. Therefore, reducing the amount of plutonium used is an effective way to reduce the cost of catalysts.