First Principles Study On Hydrogen Adsorption Properties Of Mg/Ni Interface

Mg-based material is regarded as being a very promising hydrogen storage material,howerver,the temperature of absorption/desorption is so high that limit its practical application.In this work,First principle caculation method is carried out to investigate system stability and hydrogen absorption performance about Ni-doped Mg matrix phase,(0001) surface and Mg(0001)/Ni(111) interface.We analyze hydrogen absorption mechanism of Mg-Ni system through caculate the formation energy of doped-system and Mg/Ni interface,adsorption energy of H atom,atomic interaction and electronic structure in the sysytem structure.We hope our result can provide theortical basis for improving hydrogen absorption property of Mg-based material.The result show that:First, Ni-doped Mg matrix phase and(0001) surface tend to form intermetallic compound,but the system of Ni-doped Mg bulk is not good for hydrogen absorption performance,yet with increasing of H atom number, compared to pure-Mg, absorption of doped-system is easier.When Ni doping surface,we find adsorption property with the change of doping position and quantity change,so Ni-doped surface can effectively improve the hydrogen absorption performance attributed to the bond of Mg-Ni and Mg with H,and Mg-Ni intermetallic compound help the absorption of H atom.Second, two interface matching way of Mg(0001)/Ni(111) is study, respectively AB and BA.The most stable interface structure is applied to research on interface hydrogen absorption capability.And we detect the most stable H atom adsorptive sites of both interface is top location.Comparing all location of H atom absorption,top in AB interface is the best site.Electronic structure was analysised and the H atom absorption principle about our interface is different from Mg H2 and Mg2 Ni H4,which there isnot strong Mg-H and Ni-H bonding that is reason for decreasing of system stability after H absorption. Based on structural optimization calculation and the analysis of the electronic structure of atomic position found that atom layers on either side of interface contract to the interface,and the nearer the interface, the more obvious shrinkage.Atoms near the interface layer bond strongly with H atom,and both sides of interface have the apparent trend of bonding,the same conclution is obtained by density state analysis,contrast to the bond of Mg-H、Ni-H and Mg-Mg、Ni-Ni, the link of Mg-Ni is the most intense. H atom absorption in three-layer Ni(111)/ Mg(0001)/ Ni(111) is superior to in interface Mg(0001)/Ni(111),the strong bonding between Mg,Mg-Ni intermetallic compound and H lead to system more stable.We investigate stability and absorption mechanism of hydrogen about Ni-doped Mg matrix,(0001) surface and Mg(0001) / Ni(111) interface system by the calculation of the energy and electronic structure analysis.We prove the interface of two element that can form intermetallic compounds can complete the H adsorption. Our research will play a promoting role to the practical application of Mg based hydrogen storage materials.