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Recently, Professor Jiang Jun, a member of the research team headed by Prof. Luo Yi from Hefei National Laboratory for Microscale Physical Sciences, collaborated with Prof. Zhao Wei of the National Laboratory of Microscale Physical Sciences to use the first-principles calculations to propose the first photolysis water system. The hydrogen storage hydrogen integrated material system design has the advantages of low cost, versatility, and safe hydrogen storage. The related results were published in Nature Communications under the title "Combining photocatalytic hydrogen generation and capsule storage in graphene based sandwich structures".
Hydrogen economics is one of the most "perfect" sustainable energy solutions put forward in the 1970s, envisioning a future economic structure using hydrogen as a medium (preparation, storage, transportation, and conversion). Driven by the inexhaustible sunlight, the water is decomposed into hydrogen and oxygen. Hydrogen is a kind of clean energy. It generates water by combustion and does not produce any pollutants. It achieves the goal of environmental protection and sustainable development.
However, the development of hydrogen production by photolysis has been stagnant for a long time, and the door to the era of “hydrogen energy economy†appears to have closed. The reason is that the technical bottleneck in the collection and storage of hydrogen inhibits the practical application of hydrogen production from photolysis of water. The generation of hydrogen depends on the transfer of photogenerated electrons and holes to the oxidation and reduction sites, respectively, so that the distance between the two must be smaller than the mean free path of the electrons (about 10-50 nm). Such a short interval not only results in the inevitable occurrence of a reverse reaction, but also increases the difficulty of separating and collecting hydrogen. On the other hand, safe storage of hydrogen is a long-term challenge. Hydrogen (H2) and oxygen (O2) are prone to react and produce explosions, which is very dangerous. The commonly used high-pressure liquefaction of hydrogen after the high cost of metal, inconvenient to use. Therefore, before the development of low-cost solutions for hydrogen capture and safe hydrogen storage, hydrogen production from solar photolysis cannot be effectively applied on a large scale.
In view of the serious adverse reactions in hydrogen production from photolysis of water and the difficulty of hydrogen separation and storage, the researchers have studied the work of British scientists Sir Andréheim (Nobel laureate) and Professor Wu Heng'an of the University of Science and Technology of China. Inspired: graphene can block all gases and liquids, lack of protons can be "open side", generous release. Taking advantage of this “gate of convenience†opened by nature to protons, Jiang Jun et al. designed a sandwich structure consisting of a two-dimensional carbon-nitrogen material and a graphene-based material.
Jiang Jun's research group has long been immersed in the field of photocatalytic system design and simulation, focused on the key line of electron motion, and precisely controlled the evolutionary behavior of electrons in the material system through structural design (J. Phys. Chem. Lett. 2016, 7, 1750; J. Am. Chem. Soc. 2016, 128, 8928; Angew Chem. Int. Ed. 2016, 55, 6396; Angew Chem. Int. Ed. 2015, 54, 11495), proposed a series of The experimentally proven effective photocatalytic system design. In this sandwich structure system, the carbon-nitrogen material is sandwiched between two functional group-modified graphenes. The first-principles calculations show that this system can absorb both ultraviolet and visible light, and use solar energy to generate excitons. Photoexcited excitons rapidly separate to form high-energy electrons and holes and migrate to intermediate carbon-nitrogen materials and outer graphite, respectively. On the ene material. The water molecules adsorbed on the active site of the graphene-based material are cleaved with the help of photogenerated holes and generate protons. The generated protons are driven by the built-in electrostatic field on the carbon-nitrogen material (as shown by the dipole moment), can penetrate the graphene material, move to the internal two-dimensional carbon-nitrogen material, and react to produce hydrogen after encountering electrons. . Since only the hydrogen atoms (protons) are released from graphene, the hydrogen produced by photolysis of water cannot penetrate the graphene material, resulting in hydrogen molecules produced by photolysis of water that will be safely retained in the sandwich composite system; at the same time O2, OH and other systems cannot enter the composite system, inhibiting the occurrence of reverse reactions, and achieving safe hydrogen storage at high hydrogen storage rates.
This research system subtly inhibits the occurrence of the reverse reaction of hydrogen production from photolysis of water at a low cost, and realizes the effective purification of hydrogen. This is the first design that integrates safe hydrogen production and hydrogen storage. The sandwich composite system reported in this article will not only be limited to graphene and carbon-nitrogen materials, other functional group-modified sp2 hybrid carbon materials (such as fullerenes, carbon nanotubes, etc.) and photocatalysts can also be used in this composite system. in. This will solve the two bottleneck problems of the most difficult hydrogen separation and safe storage and transportation for the realization of the conversion of solar pyrolysis water to hydrogen energy, and the large-scale application of hydrogen energy, opening the door for the start-up of the “Hydrogen Energy Eraâ€.
Relevant work was supported by the Ministry of Science and Technology's Youth 973 Project, the National Natural Science Foundation, and the Chinese Academy of Sciences' pilot project. The first author of the thesis was Dr. Yang Li, Li Xiyu, and Dr. Zhang Guozheng, PhD students in the School of Chemistry, and Jiang Jun was the author of the correspondence.
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