Theoretical Study On The Electrical And Hydrogen Storage Properties Of The C - Sub - 4 3 3 3 N

Since the graphene were found, two-dimensional materials because of the unique properties and wide attention by researchers. With dimensions as the material of the basic parameters, a series of type of graphene materials is studied and used in the industries of related interests. Graphite-like carbon and nitrogen compounds （C₃N₄ and C₄N₃） have more researched in the field of optoelectronics and were synthesis in the experiment. C₄N₃ is half metal material and has a lot more superior performance, it is suitable for spin injection into the material. Through to the two materials compression theory calculation, we can understand the material electronic structure changes and provide some theoretical cognitive for experiment and application.Using density-functional calculations （DFT）, the diversely electronic structure of graphitic carbon nitride C₄N₃, called g-C₄N₃ here, was obtained by applying biaxial compressive strain. The results show that g-C₄N₃ preserves ferromagnetic half-metallicity when the strain is lower than -2%, accompanied by the decrease of half-metallic gap. When the compressive strain ranges from -5% to -3%, the compound turns into nonmagnetic metal. With increasing the compressive strain, g-C₄N₃ turn into nonmagnetic semiconductor. Further investigations show that all nonmagnetic g-C₄N₃ behaves as a direct band gap semiconductor, and the band gap is around 1.6 eV. This fact indicates that g-C₄N₃ can be applied in spintronic field under stain environment and be tuned to suitable materials for practical application in photovoltaic field as well.When we investigation and study on g-C₄N₃, we found that it is carbon atoms replace one nitrogen atoms of g-C₃N₄. The ground state of g-C₃N₄ is Non-metallic semiconductor and the researchers have already synthesized. The g-C₃N₄ is a kind of highly efficient catalyst, it is often used in the industry in light splitting water hydrogen production and light absorption. The same biaxial compressive researched on g-C₃N₄, but the result is not satisfied.Development and utilization of new energy has always been popular science, hydrogen storage has attract more and more attention. Analogy in the study of hydrogen storage of graphene, we found that g-C₃N₄ has more advantages than graphene in hydrogen storage, such as:higher metal adsorption energy、bigger aperture structure、elevated hydrogen adsorption and adsorption density. So we held a series of studies of g-C₃N₄ to research the hydrogen storage properties.Through these study, we have some positive conclusions as following:（1） The g-C₄N₃ can exhibit half-metallic nature without any external modification, and preserve the structural and magnetic stability even at high temperature of 500 K. When it is under different biaxial strain, and three magnetic phases, nonmagnetic, antiferromagnetic, and ferromagnetic （FM） configurations are considered here.（2） The band structure of g-C₄N₃ changes with compression, from half-metal to metal phase at first, and then the indirect band gap into direct band gap.（3） Non-magnetic semiconductor g-C₃N₄ was biaxial strained and maintain the original nature, only the semiconductor band gap decreases.（4） Li atoms adsorb on both of the g-C₃N₄ and the hydrogen storage mass fraction is 9.2 wt%, which is more than the requirements of DOE.