First-principles Study Of Light-metal-decorated Phosphorene For Hydrogen Storage

Phosphorene are new two-dimensional semiconductor materials with their unique cellular geometry and tunable band gap characteristics,which have a good application prospect in the field of nanoscale electronic devices.Based on the first-principles method and the light metal atom doping decoration method,the hydrogen storage characteristics of blue phosphorene and black phosphorene are systematically studied in this paper.The main research contents and results are as follows.(1)Based on the first principles of density functional theory,taking surface decoration into consideration,the effect of single light metal(LM,include Li,Na,Ca)adatom on doping properties of blue phosphorene and black phosphorene have been studied.The calculation results show that the most stable binding position is in the hollow site when blue phosphorene decorated by Li,Na and Ca.The introduction of single Li,Na or Ca atom opens an energy band gap of 1.31 e V,1.67 e V,and 1.57 e V,respectively,presenting characteristics of N-type semiconductor.The bonding modes of Li,Na and Ca with blue phosphorene are ionic bonds.When black phosphorene decorated by Li,Na and Ca,the most stable binding position is in the hollow site.The blue phosphorene decorated by Li atoms no longer has semiconductor properties,and the introduction of single Na or Ca atom opens an energy band gap of 0.27 e V and 0.11 e V,respectively,presenting characteristics of N-type semiconductor.The bonding modes of Li,Na and Ca with black phosphorene are ionic bonds.(2)Based on the first principles of density functional theory,the hydrogen storage characteristics of light atom modified blue phosphorene and black phosphorene have been systematically studied.The calculation results show that Ca atom decorated blue phosphorene and black phosphorene could have good hydrogen storage capacity.Blue phosphorene decorated by single Li atom cannot store hydrogen stably.Blue phosphorene decorated with single Na atom can stably adsorb 2 hydrogen molecules.Blue phosphorene decorated with single Ca atom can stably adsorb 5 hydrogen molecules.Single Li atom and single Na atom decorated black phosphorene could not store hydrogen stably.Black phosphorene decorated by single Ca atom can stably adsorb 4 hydrogen molecules.(3)Furthermore,In the case of double-sided Ca atoms decorated blue phosphorene,which can absorb up to 10 hydrogen molecules,respectively,resulting in hydrogen storage capacity of 5.79 wt% with the average adsorption energy of 0.2322 e V/H2,well meeting the hydrogen storage standard set by the U.S.Department of Energy.In the case of double-sided Ca atoms decorated black phosphorene,which can absorb up to 8 hydrogen molecules,respectively,resulting in hydrogen storage capacity of 2.72 wt% with the average adsorption energy of 0.2079 e V/H2.Combined with the analysis of the bader charge population,the charge density difference and the density of states,it can be observed that the charge-induced electrostatic interaction and the orbital hybridization are the key factors of the hydrogen storage for LM adatoms-decorated blue phosphorene and black phosphorene.(4)Based on the first principles of density functional theory,the material properties and hydrogen storage properties of defective blue phosphorene and defective black phosphorenes are systematically studied.The calculation results show that in the energy band structure,the absence of a single atom causes the valence band of blue phosphorene to move up and pass through the Fermi energy level with p-type semiconductor characteristics.Black phosphorene changed from direct band gap to indirect band gap.LM atoms on defective blue phosphorene and defective black phosphorene tend to bind in the center of the defect site in an ionic bond.For LM decorated defective blue phosphorene,the point defect reduces the adsorption energy of hydrogen molecules,which has a negative effect on the hydrogen storage performance of LM decorated blue phosphorene.As for the defective black phosphorene decorated by LM,the point defect can increase the adsorption capacity of hydrogen molecules and increase the stable adsorption amount of hydrogen molecules,which has a positive effect on the hydrogen storage performance of the LM decorated black phosphorene.