Hydrogen sorption properties of Ternary Mg–Nb–O phases synthesized by solid–state reaction

Three Mg–Nb–O compounds were synthesized in order to understand the role of oxides as promoters/catalysts for hydrogen storage in Mg/MgH2 systems. Ternary Mg–Nb–O compounds were prepared by solid-state reactions. The effect of calcination temperature on phase formation and chemical composition of the solid-state products were studied by X-ray diffraction. Gradual reaction of precursor components and simultaneous formation of solid-state products were found to be strongly dependent on calcination conditions. Hydrogen sorption properties were investigated by Mass Spectrometry. MgNb2O6 and Mg4Nb2O9 phases were rather inactive with respect to hydrogen. On the contrary, Mg3Nb6O11 compound showed remarkable uptake and release of molecular hydrogen. The reversible hydrogen interaction with this phase is discussed with respect to octahedral niobium clusters present in the oxide structure.