Theoretical Design And Study Of Edge Modified Black Phosphorus Nanoribbons For Photolysis Of Water

Black phosphorus(BP)is a new type of semiconductor material,which has attracted the attention of academia due to its excellent photoelectric properties.The two-dimensional black phosphorus with nanometer thickness,also known as phosphorene,can be prepared from bulk crystals by simple mechanical exfoliation.Black phosphorus can be used to fill the gap between graphene and two-dimensional crystalline transition metals---molybdenum disulfide due to its excellent performance.With its high carrier mobility,adjustable band gap with the number of atomic layers,strong visible-light absorption characteristics,high specific surface area,and anisotropy,thus it has essential application prospects in various fields,such as solar cells,energy storage,sensors,field-effect transistors,biomedicine,and environmental protection.The same material with different dimensions also displays different physical properties.Based on two-dimensional black phosphorus,two typical edge black phosphorus nanoribbons: zigzag black phosphorus nanoribbons(ZPNRs)and armchair black phosphorus nanoribbons(APNRs),can be obtained by cutting along the non crystalline direction.Due to the quantum confinement effect and unique edge effect,black phosphorus nanoribbons show better performance than the original black phosphorus in some dimensions.For instance,theoretical studies have proved that black phosphorus nanoribbons with suitable size have excellent visible light absorption characteristics and energy band structure suitable for photolysis of water and have great application prospects in photolysis catalysis.Although the theoretical research of black phosphorus nanoribbons has been reported,most of them are completed based on hybrid functional theory,which could well describe the electronic structure of bulk materials.Nevertheless,considering the low dimensional materials,hybrid functional theory methods often deviate greatly from experiments and many body perturbation theory methods based on Green’s function and even draw opposite conclusions.This thesis utilizes the many body perturbation theory method(MBPT)based on Green’s function to investigate the structural system of black phosphorus nanoribbons which are passivated and modified by hydrogen(H),fluorine(F),chlorine(Cl),and pseudo-halogen chemical groups(CN)through GW approximation.Our results show that the dielectric environment of black phosphorus nanoribbons,such as the length of the nanoribbons,the number of layers of the nanoribbons,and the significant impacts of band edge modification of the nanoribbons on their electronic structures.Based on a comprehensive understanding of the regulation law of black phosphorus nanoribbons dielectric environment on its electronic structure,we designed several bilayer black phosphorus nanoribbons heterojunctions based on van der Waals force via regulating the orientation of black phosphorus nanoribbons and band edge modifiers,which are suitable for photolytic water energy band structure.In specific,when one atomic layer in the heterojunction rotates 90 degrees relative to the other,the bilayer heterojunction has excellent comprehensive photocatalytic performance.On the other hand,our calculation results also indicate that black phosphorus nanoribbons still have the ability to photolysis water even if they are partially oxidized under natural conditions.In conclusion,this research not only understands the regulation of the dielectric environment of black phosphorus nanoribblons on their electronic structures,but further theoretically predicts several bilayer black phosphorus nanoribblons heterojunctions with suitable band structures for water splitting.Our work provides the theoretical guidance and foundation for developing metal-free photocatalysts in the future.