Structural and electrochemical properties of MgNi-based alloys with Ti, Pt and Pd additives

This work reports the results on the structural and electrochemical properties of MgNi-based hydrogen storage alloys prepared by ball milling, in which electroless and electrochemical depositions of palladium and copper were made on the surface of the particles. Copper and palladium layers were produced by the reduction of CuSO4 and PdCl2 salts, respectively. The physical properties of the base alloys, Mg50Ni50 and Mg50Ni50+10wt% of Ti or Pt, before and after the deposition process of Pd and Cu were characterized by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) at the Ni K-edge. For all alloys, XRD and extended X-ray absorption fine structure (EXAFS) results have shown the presence of a predominant amorphous structure. X-ray absorption near edge structure (XANES) results showed that the introduction of Ti and Pt did not affect the electronic properties of the Ni atoms in the alloys and that the Ni atoms are appreciably oxidized during the electroless deposition of Cu and Pd. On the other hand, for electrochemically Cu- and Pd-coated Mg50Ni50 alloys there are only minor changes in the electronic properties of the Ni atoms. In all cases, it is observed that the introduction of Pt and/or the Pd electrochemical coating of the particle surface improves the cycling stability of the alloys.