Two-Dimensional Graphitic Carbon Nitride As The Gas Separation Membrane For H₂/CO: A Density Function Theory Investigation

Fossil fuels belong to non-renewable energy,dust particles and greenhouse gases are the culprits leading to the haze and global warming.In the face of energy crisis and environmental pollution,clean energy has drawn public attention.Hydrogen energy is a kind of secondary energy which is high in combustion efficiency and clean and pollution-free.It can meet the requirement of economy development.The sustainable development of hydrogen energy involves the production storage,transportation,utilization of hydrogen and a series of problems,the current production of hydrogen in the industry is mainly on the natural gas reforming and coal gasification of the mixed gas separation,the production process will be mixed with other gases,reducing the purity of hydrogen.At present,the main methods of separating hydrogen are pressure swing adsorption method,cryogenic separation method and membrane separation technology.Because of the advantages of high efficiency,low energy consumption,small space occupancy,no material before and after separation and low cost of equipment,Membrane separation technology has become One of the best prospects for the development of the best technology.The core of the membrane separation technique is to select an ideal separation membrane material with high selectivity and high permeability.The permeability of the membrane material is inversely proportional to the thickness of the membrane.By reducing the thickness of the separation membrane,the permeation flux of the gas can be increased,The two-dimensional graphite phase carbon nitride crystal belong to the single-electron thickness of the two-dimensional thin film material,in the crystal structure,surrounded by the six-ring pore size appropriate,The graphite is more suitable for use as a membrane material for the separation of hydrogen.In this paper,two-dimensional graphite carbon nitride g-C₃N₄ crystal and g-C10N13 crystal were studied.Based on the first-principles method of density functional theory,the triazine and heptazine structures of two-dimensional g-C₃N₄ crystals and two-dimensional g-C10N13 crystal separation of H₂ and CO gas feasibility.For the two-dimensional g-C₃N₄ crystal,the interaction between the two chains in the process of the separation of H₂ molecules,the interaction between the two systems can be exceed the energy of H₂ molecules mostly.The charge transfer between the N atom and the H₂ molecule in the two-dimensional g-C₃N₄ crystal,and the chemical adsorption between the H₂ gas and the two-dimensional g-C₃N₄ crystal can not be crystallized.For the heptazine structure,the interaction between the H 2 molecules in the system through the two-dimensional g-C₃N₄ crystal is very weak,and there is no chemical adsorption with the crystal,can successfully penetrate the two-dimensional g-C₃N₄ crystal micropore,the horizontal position of the CO molecules close to the crystal micropore and the charge transfer between the crystal occurs,the partial adsorption of some CO molecules and crystals makes it impossible to go through the two-dimensional g-C₃N₄ crystal micropore smoothly.In the system where the H₂ molecules go through the two-dimensional g-C10N13 crystal,the relative position of the gas molecules has little effect on the interaction energy.The two gas molecules are not charged with the atoms between the crystal,H₂ and CO molecules can penetrate the micropore of two-dimensional g-C10N13 crystal.so the two-dimensional g-C10N13 crystal does not have the separation of H₂ / CO gas required for selective permeability.The two-dimensional heptazine structure g-C₃N₄ crystal can be considered as a separation membrane material for separating H 2 and CO gas molecules.