Abstract
The hydrogen adsorption characteristics and mechanism of transition metal-doped zeolite template carbon (ZTC) as a novel porous material are studied by theoretical calculations employing first-principle all-electron atomic orbital method based on density functional theory. The stability of transition metal atoms (Sc, Ti, and V) decorated on zeolite template carbon is investigated by calculating the absorption binding energy. The adsorption configurations of the doped metal atom and adsorbed hydrogen are obtained from the energy functional minimization of first-principles calculations. The underlying mechanism for improving hydrogen storage performance of ZTC by doping transition metal atoms are explored through analyzing charge/spin populations of metal atoms in combination with the calculated results of hydrogen adsorption quantity and binding energy. To improve the hydrogen storage capability, the Sc, Ti, and V are individually introduced into the ZTC model according to the triplex axisymmetry. The hydrogen storage properties of ZTC decorated with different metal atoms are characterized by the adsorption energy and structure of several hydrogen atoms. The more energetically stable complex system with higher binding energy and adsorbing distance of hydrogen than lithium-doped ZTC can be achieved by doping Sc, Ti, V atoms in ZTC, which is expected to fulfill the substantial safe hydrogen storage by increasing hydrogen capacity with multi-sites doping of transition metal atoms. The present investigation provides a theoretical basis and predictions for the following experimental research and design of porous materials for hydrogen storage.
Highlights
At present, hydrogen storage techniques are primarily classified into physical and chemical schemes
At various sites are studied by employing the all-electron numerical orbital first-principles calculations at various sites are studied by employing the all-electron numerical orbital first-principles based on density functional theory, being analyzed by calculating the binding energy of complex calculations based on density functional theory, being analyzed by calculating the binding energy of metal-decorated structure and H2 adsorption for four representative absorbing sites according to the complex metal-decorated structure and H2 adsorption for four representative absorbing sites three-fold rotational symmetry of zeolite template carbon (ZTC)
The transition metal atoms and H2 molecules introduced onto A1, A3, A4 and A10 sites in ZTC respectively, and the geometric optimization has been are subsequently introduced onto A1, A3, A4 and A10 sites in ZTC respectively, and the geometric performed to obtain metal coordination structures and H2 multiple-molecule adsorption configurations
Summary
Hydrogen storage techniques are primarily classified into physical and chemical schemes. Because of the evident difference in electronic structure between transition metal and lithium atoms, especially for the unsaturated d-orbital electrons of transition metal atom which can produce a stronger force similar to coordinating bond than main group metal, it is reasonably suggested that the hydrogen storage performance of ZTC being doped with transition metal atoms will be improved more obviously compared with main-group metal. Triggered by this inspiration, the present paper proposes to modify. The optimum adsorption position and quantity of hydrogen molecules around the doped metal atoms are studied to found a theoretical basis for experiments and explore the transition metal-decorated ZTC porous materials applied in hydrogen storage
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