Electrodeposited Preparation And Characteristics Of La-Mg-Ni Hydrogen Storage Alloy

Hydrogen storage alloy has been applied widely in Ni-MH battery and other affairs.With the development of application of hydrogen storage alloy, it is specially necessaryhow increases the capacity of hydrogen storage that can be required. Recent studiesdemonstrated that Ni-MH battery which is added rare earth will obtain higher capacity andlonger cycle life. The La-Mg-Ni system hydrogen storage alloy has a perfect applicationforeground that can be used as the cathode of Ni-MH battery，because of its high capacityand good activation performance．Presently，La-Mg-Ni system hydrogen storage alloy aspowder-like or piece-like in shape can be made by melting，mechanize or burning knot.However, these methods have high cost and complicated equipment. Electrodeposited inaqueous solution system provides several advantages such as simple equipment, low cost,easy operating, sedimentary conditions and craft parameter easy to control.In this work, La-Mg-Ni alloy film was prepared by galvanostatic electrodeposition inaqueous. By means of cyclic voltammetry（CV）, Tafel polarization curve, cathodepolarization curves and electrochemical impedance spectroscopy（EIS）, electrochemicalperformance of the alloy film was studied. Sanning electronic microscope（SEM）, energydistribution spectrum（EDS） and X-ray diffractometer（XRD） were used to research thephase structure, component and composition.The results showed that the characteristic peak of electrodeposited alloy films inaqueous solution system can be seen from the XRD patterns, which has strong LaMg₂Ni₉peaks. Amorphous deposit obtained in adding NaH₂PO₂, and has a stronger activities ofantioxidase. Adding C₆H₄SO₂NNaCO·2H₂O to the baths, the loose of electrodepositedalloy films has decreased, the roughness, adhesion and crystalizaiton index of alloy films isbetter, those facilitate the formation of LaMg₂Ni₉phase. The better technology parameters:the deposition current density is40A/dm², the deposition temperature is20℃, LaCl₃·7H₂Ois3g/L, MgCl₂·6H₂O is10.5g/L, NiCl₂·6H₂O is30g/L, C₆H₈O₇·H₂O is30g/L, NH₄Cl is11g/L, NaH₂PO₂is13.5g/L, C6H4SO₂NNaCO·2H₂O is0.60g/L, H₃BO₃is44g/L. The alloyfilm obtained at this technology parameters was dark gray, the apparent activation free energy reaches to40.78kJ/mol, the potential for hydrogen evolution reaches to-0.22V,Hydrogen evolution current density j0is1.71×10^-3A/cm², indicating it has higherhydrogen evolution activity; the electrode adsorption degree Q is7.20×10^-2F·cm^-2, theroughness on the surface is larger, indicating the film has better hydrogen storage function.The deposition rate of alloy films is higher, the degree of cathode polarization is smaller.