A DFT study of hydrogen adsorption kinetics and thermodynamics on mixed oxides of Mg0.5Ni0.25O1.13

Hydrogen sorption mechanism, kinetics and thermodynamics of hydrotalcite derived mixed oxides of Mg0.5Ni0.25O1.13 have been studied using the density functional theory. Hydrotalcite based magnesium 0.5 0.25 0.25 1.13 and nickel and aluminum containing mixed oxides showed significant hydrogen sorption kinetics and thermodynamics. Reduced mixed oxides or active metals of Magnesium (Mg) and Nickel (Ni) converted to hydrides of MgH2 and Mg2NiH4. The study indicated the favorable hydrides formation which is due to the electrostatic interaction and strong hydrogen bonding type interaction between them. The materials itself facilitate to diffuse hydrogen molecules to different layers of the materials and enhances the sorption kinetics. Hydrogen adsorption and desorption energy of MgH2 and Mg2NiH4 are 60.13, 64.31, 40.22 and 45.72 kJ/mol, respectively. Model predicted values of hydrogen adsorption enthalpy and entropy changes of MgH2 and Mg2NiH4 are -48.18 Kj/mol, -135j/mol.K, -55.10 Kj/mol and -155 J/mol.K, respectively. The rate constant of adsorption are 6.0×1012 and 1.3×1013 sec-1 for MgH2 and Mg2NiH4 hose are indicating physical and chemical adsorption of hydrogen. © Medwell Journals, 2017.