Change a 'membrane' fuel-powered car can go further

Schematic diagram of protons passing through the graphene membrane. The picture is supplied by the interviewee. The new fuel cell vehicle as a new energy electric vehicle can be filled with fuel in just one or two minutes. The core component is the fuel cell. The conductivity of the proton conductive membrane To a large extent, it affects the energy conversion efficiency of fuel power cells. Recently, Professor Zhang Sheng from the School of Chemical Engineering of Tianjin University and the Nobel Prize winner Sir Andre u0026middot; Heim of the University of Manchester in the United Kingdom and others have confirmed that two-dimensional materials such as graphene and boron nitride have proton conductivity and further discovered , The high-temperature proton exchange membrane of mica used in fuel power cells, which is widely existing in nature, has better performance than current commercial membranes, and is more energy-saving and environmentally friendly. These two research results were recently published in 'Nature u0026middot; Nano' and 'Nature u0026middot; Communication'. Looking for a thinner membrane to increase the cruising range. It is reported that compared with the current common household lithium-ion electric vehicles, fuel-powered battery vehicles save a long charging time and can be filled with fuel in just one or two minutes. At the same time, fuel-powered battery vehicles do not undergo a thermal engine process, are not restricted by thermal cycles, have extremely high energy conversion efficiency, and have a longer battery life. The product of the fuel-powered battery power generation process is only water, which is more environmentally friendly. Therefore, fuel-powered battery vehicles have become the future of automobiles. One of the important development directions. The working principle of the fuel power cell is that the anode fuel hydrogen loses electrons and becomes protons, and then passes through the proton exchange membrane to reach the cathode and combines with oxygen and electrons to form water. The protons are transmitted inside the battery and form a current loop with the electrons in the external circuit. The energy conversion efficiency of fuel power cells is very critical. At present, the thickness of commercial perfluorosulfonic acid proton conducting membrane is at least 5 microns, and it must be in a hydrated state below 100°C before it can be used. At this time, the purity of hydrogen is relatively high. The development of membrane materials that can efficiently conduct protons above 100°C will help improve fuel power cell efficiency, reduce hydrogen purity requirements, simplify water management systems, and achieve the purpose of reducing costs and reducing pollution. The business development of the company is of vital importance. It is not easy to find high-efficiency high-temperature proton-conducting membrane materials. Zhang Sheng analyzed that this material is not only required to be thin, but it also has to block the penetration of hydrogen while allowing protons to pass through at high speed. The permeation of hydrogen will cause side reactions, reduce the battery output voltage, and affect the overall reaction efficiency of the fuel power cell. At the same time, it also needs to have the characteristics of high temperature resistance. Two-dimensional materials such as graphene are ideal materials. Zhang Sheng first prepared micron-level single-layer graphene and boron nitride films with his collaborators, with a thickness of about 0.3 nanometers (1 nanometer equals 0.001 micrometers), and placed the two sides of the film separately In hydrochloric acid solutions of different concentrations, due to the existence of a concentration gradient, the ions on the side with higher concentration will diffuse to the side with lower concentration, and the movement of the ions forms an electric current. They calculated based on theory that two-dimensional materials such as graphene and boron nitride with a hexagonal grid structure only allow particles with a diameter of less than 10 picometers (1 picometer is equal to one thousandth of a nanometer) to pass through due to their special physical structure. . Hydrochloric acid is composed of hydrogen ions and chloride ions. The proton radius is about 0.001 picometers and the chloride ion radius is about 180 picometers, so only smaller protons can pass through the membrane. This proves that the current passing through the two-dimensional thin film in this experiment is all initiated by proton conduction, while the slightly larger chloride ion does not contribute at all. Zhang Sheng said: This test proves that graphene and boron nitride two-dimensional materials only allow protons to pass, and can block the passage of other ions and molecules, including hydrogen, which meets the requirements of fuel power cell proton conducting membrane materials. But he also said frankly that although graphene and boron nitride are thinner than commercial proton-conducting membranes (a difference of 10,000 times), their structure is too dense, causing the proton-conducting resistance to be greater than commercial membranes, and the energy conversion efficiency has not been improved. Commercial promotion. Mica film is more promising than graphene. On the basis of confirming that two-dimensional materials such as graphene can be used as proton conducting materials, Zhang Sheng and his collaborators found that another two-dimensional material mica is more effective than graphene after two years of active exploration. The fuel power battery category is more promising. Mica is a kind of mineral with extremely abundant reserves and very low price in the earth's crust. Its main body is composed of an aluminosilicate layer like a sponge, and potassium ions are abundantly present in the pores like water. Zhang Sheng analyzed that due to the ion exchange reaction, potassium ions can be easily exchanged with protons. Because the radius of potassium ions is about 100 picometers, and the radius of protons is about 0.001 picometers, the volume is much smaller, so protons can be transported well in the pores where potassium ions are located. The study found that the proton conductivity of the mica membrane after the ion exchange solution is greatly improved, and the use temperature can be extended from 100°C to 500°C, which is very promising. Zhang Sheng explained: We found that the proton conductivity of the mica membrane after the ion exchange reaction has increased by 100 times. At the same time, the mica film has higher thermal stability, abundant reserves and low price. The study also found that at the current temperature of 150°C, the proton conductivity of the mica membrane is more than twice the current commercial requirement. After being used in fuel power cells, the mileage of cars will be greatly improved. At present, Zhang Sheng is leading a research team to prepare large-scale mica films, using its efficient proton conductivity and excellent heat resistance to improve the existing fuel power cell technology and promote the development of fuel cell vehicles. In addition to fuel power cells, Zhang Sheng also plans to use the above-mentioned proton-conducting membrane materials for solar energy photolysis water, ocean blue energy extraction, and electrochemical conversion of carbon dioxide into many clean energy technologies such as formic acid, ethanol, ethylene and other chemical raw materials.