On November 16, the reporter learned from Tianjin University that Professor Zhang Sheng of the School of Chemical Engineering of the school collaborated with Professor Andre Heim, the Nobel Prize winner in physics at the University of Manchester, and confirmed the two-dimensionality of graphene and boron nitride. The selectivity of hydrogen ion transport in the material was 100%, and it was found that mica can be used as a high-temperature proton exchange membrane for fuel cells. These two research results are expected to promote the commercial development of hydrogen fuel cell vehicles.
Zhang Sheng said: "The proton conductivity of the mica film has increased by 100 times, which is encouraging. At present, graphene is considered to be a promising proton conductive material, and our research found that mica may be more than graphene. Promising because of its better proton conductivity, higher thermal stability, and abundant reserves at a low price. "The study also found that at 150 ° C, the proton conductivity of the mica membrane exceeds twice the current commercial requirements. In other words, after using it for fuel cells, the mileage of the car will also be greatly improved.
According to Zhang Sheng, compared with the current lithium-ion battery electric vehicles, hydrogen fuel cell vehicles have a shorter charging time, only one or two minutes to fill up the fuel, and the energy conversion efficiency is extremely high and the battery life is longer. The working principle of the core component fuel cell is that hydrogen loses electrons to become hydrogen ions, and then passes through the proton exchange membrane to be transmitted inside the battery to form a complete current loop. Therefore, the hydrogen ion conductivity of the proton conductive membrane greatly affects the energy conversion efficiency of the fuel cell. At present, the thickness of commercial proton conductive membranes is at least 5 microns or more. If thinner membrane materials can be developed, it will help to improve the proton conductivity and have an important promotion significance for fuel cell vehicles.
The research team prepared micron-scale single-layer boron nitride films, and according to the theoretical calculations, two-dimensional materials such as graphene and boron nitride with a hexagonal grid structure only allowed particles with a diameter of less than 10 picometers to pass through. Their experiments found that all the current through the boron nitride film is generated by hydrogen ion conduction. "This is not only an important progress in our understanding of the interaction between protons and thin films, but also important for basic research and application development of graphene and other two-dimensional materials in the field of efficient membrane separation." Zhang Sheng said.
Further research found that although graphene, boron nitride, etc. have the property of allowing only hydrogen ions to pass through, their transmission resistance is high, and the conduction speed of hydrogen ions is slow, which is not suitable for commercial promotion. To this end, the research team developed a new proton conductive membrane material with high proton conductivity-mica membrane. The study found that the proton conductivity of the treated mica film has been greatly improved, and the use temperature has been extended from 100 ℃ to 500 ℃, which has great application prospects.
At present, the research team is preparing large-scale mica membranes, using its efficient proton conductivity and excellent heat resistance, to improve the existing fuel cell technology, and promote the development and improvement of fuel cell vehicles. In addition, the membrane material can also be used in flow batteries, solar photolysis water, ocean blue energy extraction, and the electrochemical conversion of carbon dioxide to formic acid, ethanol, ethylene and other clean energy technologies. (Author: Chen Fei Zhang)
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