First-principles Study On The Performance Of Electrocatalytic Hydrogen Evolution Reaction And Hydrogen Storage Of Defective Blue Phosphorene Monolayer

Blue phosphorene,as one of the isomers of black phosphorene,is an emerging nanomaterial with numerous excellent physical properties such as structural stability,multiple surface pores,large specific surface area and strong tunability,which has broad research prospects in the fields of hydrogen storage and electrocatalysis.Based on the first-principles calculation method of density generalization theory(DFT),the effect of modification of metal atoms(Li,Ca),defect engineering,atomic doping and strain modulation on the electronic properties as well as the hydrogen storage and electrocatalytic hydrogen desorption properties of blue phosphorene monolayers was systematically investigated in this paper.The main study and results are as follows:(1)The pristine blue phosphorene(Blue-p)monolayer,defective blue phosphorene monolayers and nonmetal atom-doped blue phosphorene monolayers were systematically investigated for their geometrical structures and electronic properties.Four structures of Stone-Wales defects(SW),single defects(SV),and double defects(DV and DV2)were considered for the defect structure,and boron-doped blue phosphorene(B@BlueP)and nitrogen-doped blue phosphorene(N@BlueP)monolayers were considered for the doping structure.The results show that the Blue-p monolayer is a nonmagnetic indirect bandgap semiconductor with a bandgap width of 1.93 eV,while the bandgap structure is transformed by the introduction of defective structures or the substitutional doping of nonmetallic atoms.Specifically,the defective structures SW,DV and DV2 as well as the doped structures B@BlueP and N@BlueP still maintain the semiconductor nature,but the band gaps are reduced to 1.28 eV,0.34 eV,1.26 eV,1.27 eV and 0.91 eV,respectively,with the SV exhibiting metallicity.(2)We investigated the effects of vacancy defects and biaxial strain on the HER activity of blue phosphorus monolayers.The results show that the defective structure provides more active sites for the hydrogen evolution reaction and more efficient catalytic activity,especially the SV defective structure exhibits the same efficient HER catalytic performance as the catalyst Pt.Biaxial strain can also change the HER activity of blue phosphorus.The Gibbs Free-Energy(ΔGH*)value of DV2 varies linearly with the intensity of the strain to be received,and when the strain reaches 2.4%,the ΔGH*value converges to 0 eV,exhibiting extremely high catalytic activity.The pz band centers(εpz)of the SV monolayer and the DV2 monolayer with biaxial strain were calculated respectively.The results suggest that the pz-band center(εpz)can be regarded as an ideal descriptor for the HER activity of the blue phosphorus structure.(3)The structural and electronic properties of alkali metal Li atom decorated with pristine blue phosphorene(Li/BlueP-p)and defective blue phosphorene(Li/SW,Li/SV,Li/DV2)monolayers as well as alkaline earth metal Ca atom decorated with SV-defective blue phosphorene(Ca/SV)and nonmetal atom-doped blue phosphorene(Ca/B@BlueP and Ca/N@blueP)monolayers were systematically investigated.It is shown that metal atoms have difficulty in forming strong bonds with the Blue-p monolayer,resulting in the diffusion of metal atoms to form cluster structures easily.Whereas,the interaction between metal atoms and blue phosphorene monolayer is significantly strengthened by introducing defects and non-metal atoms,and the binding energies are all over the bulk phase cohesion energy.Whereas,the interaction between the metal atoms and the blue phosphorene monolayer is significantly enhanced by the introduction of defects and non-metallic atoms.The study of the electronic structure shows that the band gap of the system is further reduced due to the decoration of the metal atoms,and one of the systems,Li/DV2,Ca/SV and Ca/N@BlueP,exhibits metallic properties.Besides,there is an orbital hybridization and charge transfer between the metal atoms and the monolayer,which result in a local electric field favoring the adsorption of H2 molecules.(4)We systematically investigated the hydrogen storage properties of metal-atom decorated defective blue phosphorus and atom-doped blue phosphorus systems.The results show that the hydrogen storage capacity of the systems with metal atom decoration has significantly increased,in which the B@BlueP system decorated with Ca atom can stably adsorb six H2 molecules,and the theoretical hydrogen storage capacity can reach 7.29 wt%for the two-sided decoration,with a great thermal stability.The analysis of differential charge density and electronic density of states reveals that both the polarization mechanism of H2 molecules and the weaker orbital hybridization are responsible for the adsorption of H2 molecules.The effect of temperature and pressure on the hydrogen storage performance is also investigated,and the results indicate that the H2 storage systems can be stable at room temperature and low pressure,and thus the practical reversible hydrogen storage can be achieved at room temperature.