What kind of structure is used for proton exchange membranes and their subsystems

Hydrogen fuel cells are a type of proton exchange membrane fuel cell. (1) Hydrogen reaches the anode through a pipeline or gas guide plate, and under the action of the anode catalyst, the hydrogen molecule dissociates into positively charged hydrogen ions (i.e., protons) and releases negatively charged electrons. (2) hydrogen ions pass through the electrolyte (proton exchange membrane) to the cathode; The electrons travel through an external circuit to the cathode.

The electronic external circuit forms an electric current, which can be used to output electrical energy to the load through appropriate connections. (3) At the other end of the battery, oxygen (or air) reaches the cathode through the pipe or air deflector; Under the action of the cathode catalyst, oxygen reacts with hydrogen ions and electrons to form water. Proton exchange membranes are used in hydrogen fuel cells, which can improve efficiency and ensure that hydrogen and oxygen react completely (basically completely).

The efficiency of hydrogen fuel cells can reach more than 60%, and there are now catalysts that do not use platinum, and the efficiency of internal combustion engines is limited by the Carnot cycle, so there is an upper limit to its efficiency and it is always low. (Fujian Yanan Group is a leading provider of clean energy solutions and an enterprise dedicated to the industrialization of hydrogen fuel cells.) Ya Xiaonan answers 4000-080-999).

Stationary long-life power supplies offer the highest power density over the longest service life and have been proven to last more than 10,000 hours of continuous use, and design improvements have been continuously improved to contribute to the commercial success of the stationary PEM fuel cell industry. Portable power supplies make portable fuel cell devices smaller and more powerful, and these components enable fuel cell dry reactive gases to work excellently and achieve durable power densities that meet the requirements of the most challenging applications. Utility power supplies offer maximum power density and durability in harsh (hot and dry) automotive environments.

These components can operate in hotter and drier operating conditions, enabling smaller fuel cell packs with a more streamlined system and more power.

A high-equilibrium modified membrane containing ionic groups that selectively permeabilizes ions in solution. Because it is generally used in applications to select its ion permeability, it is also called ion selective permeability membrane.

Preparation method: There are two types of ion exchange membranes: homogeneous membranes and heterogeneous membranes, which can be manufactured by polymer processing and molding methods.

Homogeneous membranes. First, the film is made of polymer materials such as styrene-butadiene rubber, cellulose derivatives, PTFE, polychlorotrifluoroethylene, polyvinylidene fluoride, polyacrylonitrile, etc., and then monomers such as styrene and methyl methacrylate are introduced to polymerize into polymers in the film, and then through chemical reactions, the required non-beat functional groups are introduced. Homogeneous membranes can also be obtained by direct polymerization of monomers such as formaldehyde, phenol, phenol sulfonic acid, etc.

Heterogeneous films. It is processed into a film after fully mixing ion exchange resin with a particle size of 200 400 mesh and ordinary film-forming polymer materials, such as polyethylene, polyvinyl chloride, polyvinyl alcohol, fluoroelastomer, etc. Both homogeneous and heterogeneous membranes must be kept in water because they will dry out in the air and become brittle or cracked.

Ion exchange membranes can be assembled into electrodialyzers for desalination of brackish water and concentration of salt solutions. The degree of desalination of electrodialysis units can reach the purity of primary distilled water. It can also be used for the desalination of glycerol and polyethylene glycol, the separation of various ions and radioactive elements, isotopes, and the separation of amino acids.

In addition to this rule, ion exchange membranes are also used in the purification of organic and inorganic compounds, in the treatment of radioactive waste in the nuclear energy industry and in the preparation of nuclear fuel, as well as in fuel cell separators and ion-selective electrodes. Ion exchange membranes occupy an important position in the field of membrane technology, and it will also play an important role in biomimetic membrane research.

Improvement and application of proton exchange membrane materials.

Proton exchange membrane fuel cells have the advantages of low operating temperature, fast starting, high specific power, simple structure, and convenient operation, and are recognized as the preferred energy source for electric vehicles and stationary power stations. Inside the fuel cell, the proton exchange membrane provides a channel for the migration and transport of protons, so that the protons pass through the membrane from the anode to the cathode, and the electron transfer of the external circuit forms a loop, providing current to the outside world, so the performance of the proton exchange membrane plays a very important role in the performance of the fuel cell, and its quality directly affects the life of the battery.

So far, the most commonly used proton exchange membrane (PEMFC) is still DuPont's NAFION membrane, which has the advantages of high proton conductivity and good chemical stability. However, there are still the following shortcomings of Nafion-like films: (1) it is difficult to make and costly, the synthesis and sulfonation of perfluorinated substances are very difficult, and the hydrolysis and sulfonation in the film-forming process are easy to denature and degrade the polymer, which makes the film-forming difficult and leads to high cost; (2) The optimal working temperature of Nafion series membranes is 70 90, which will cause the water content to decrease sharply and the conductivity to decline rapidly, which hinders the problem of increasing the electrode reaction speed and overcoming catalyst poisoning by appropriately increasing the working temperature; (3) Some hydrocarbons, such as methanol, have high permeability and are not suitable for use as proton exchange membranes for direct methanol fuel cells (DMFCs).

Therefore, research is ongoing to improve the performance of proton exchange membranes. Judging from the literature reports in the past two years, the following methods can be used to improve the method:

1) Organic-inorganic nanocomposite proton exchange membranes, which rely on the characteristics of small size and large specific surface area of nanoparticles to improve the water-holding capacity of composite membranes, so as to achieve the purpose of expanding the working temperature range of proton exchange membrane fuel cells;

2) To improve the bone frame material of the proton exchange membrane, aiming at the shortcomings of the most commonly used Nafion membrane, or improve on the basis of the Nafion membrane, or choose a new skeleton material;

3) Adjust the internal structure of the membrane, especially increase the micropores in it, so as to facilitate the formation of the film and solve the problem of catalyst poisoning.

In addition, in addition to these three improvements, many existing studies have adopted nanotechnology to a greater or lesser extent, making materials smaller and with better performance.

It is a membrane that allows only water and protons (or hydrated protons, H3O+) to pass through.

The principle is simply as follows: hydrated protons bind to sulfonic acid groups in the proton exchange membrane, then move from one sulfonic acid group to another, and finally reach the other side.

Proton exchange membrane fuel cells have become the most competitive clean alternative power source for gasoline internal combustion engine power. The material used as PEM should meet the following conditions:

1) Good proton conductivity;

2) The electroosmosis of water molecules in the membrane is small;

3) the permeability of the gas in the membrane is as low as possible;

4) Good electrochemical stability;

5) Good dry-wet conversion performance;

6) It has a certain mechanical strength;

7) Good machinability and appropriateness.

At this stage, it is divided into: perfluorosulfonic acid proton exchange membrane; Nafion™ recast films; non-fluoropolymer proton exchange membranes; new composite proton exchange membranes and more.