Effect of addition of Mn and Co on the hydrogen storage characteristics of microcrystalline Mg

Microcrystalline magnesium containing Mn and Co (Mg(Mn) and Mg(Co)) has been prepared by an arc vaporization-condensation method. The average crystal size of Mg(Mn) and Mg(Co) produced by this method is ∼50 nm. XRD patterns indicated that the main phase of the resulting microcrystalline Mg remained the hexagonal crystal structure and the lattice constants keep the same values as the pure microcrystalline Mg. This means no Mn or Co enters the Mg lattice. XRD results also showed that the main product of Mg(Mn) and Mg(Co) is MgH ₂ after hydriding. The TEM micrographs showed that some wadding was inlaid on the surface of the microcrystalline Mg. The Mg(Mn) and Mg(Co) absorbed and desorbed hydrogen more easily than pure microcrystalline Mg with the aid of Mn and Co. The complete desorption curves (P-C-T curves) with a wide pressure plateau can be obtained at 280 °C. The reversible capacity of hydrogen reached 700 cm³ g^-1 (STP), i.e. 6.2wt.% based on Mg(Mn) or Mg(Co).