Abstract
First-principles calculations were used to study the energetics and electronic structures of Ni and Sc co-doped MgH2 system. The preferential positions for dopants were determined by the minimal total electronic energy. The results of formation enthalpy indicate that Ni and Sc co-doped MgH2 system is more stable than Ni single-doped system. The hydrogen desorption enthalpies of these two hydrides are investigated. Ni and Sc co-doping can improve the dehydrogenation properties of MgH2. The lowest hydrogen desorption enthalpy of 0.30 eV appears in co-doped system, which is significantly lower than that of Ni doping. The electronic structure analysis illustrates that the hybridization of dopants with Mg and H atom together weakens the Mg-H interaction. And the Mg-H bonds are more susceptible to dissociate by Ni and Sc co-doping because of the reduced magnitude of Mg-H hybridization peaks. These behaviors effectively improve the dehydrogenation properties of Ni and Sc co-doped cases.
Highlights
Hydrogen energy with high efficiency and pollution-free characteristics [1]-[5], is considered to be one of the most promising candidates to replace fossil fuels
We have studied the preferential sites of Ni and Sc dopants on MgH2 depending on the minimization of total electronic energy
The Ni and Sc co-doping effects on the energetics and electronic structures of MgH2 were studied by the first-principles calculations based on density functional theory (DFT)
Summary
Hydrogen energy with high efficiency and pollution-free characteristics [1]-[5], is considered to be one of the most promising candidates to replace fossil fuels. Reducing the grain size [7]-[9], and introducing transition metals (TM) or transition metals oxides [10]-[14], can effectively improve the absorption/desorption kinetics of MgH2 Among these two methods, the introduction of transition metals into MgH2 has played a vital role in the development of Mg-based hydrogen storage materials. Despite the many experimental and theoretical studies of co-doped MgH2 hydrogen storage system, there is still a lack of systematic study of the structural, bonding and hydrogen desorption properties of co-doped MgH2 with Ni and Sc. in this paper, we conducted a systematic study on the effects of Ni and Sc co-doped on MgH2 using first-principles calculations. Electronic structures were analyzed to identify the intrinsic mechanisms of interactions between Mg and dopants and the desorption of hydrogen on co-doped system
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