Effect of Titanium additive element on the discharging behavior of MgNi Alloy electrode

Mg0.90Ti0.10Ni, Mg0.85Ti0.15Ni, Mg0.80Ti0.20Ni, Mg0.90Ti0.15Ni0.95, Mg0.90Ti0.20Ni0.90 and Mg0.95Ti0.15Ni0.90 ternary alloys were synthesized by mechanical alloying and their electrochemical hydrogen storage characteristics were investigated. Among the Mg–Ti–Ni ternary alloys Mg0.90Ti0.20Ni0.90 alloy showed the best discharge performance. The initial discharge capacity was observed to depend on Mg/Ni atomic ratio rather than Ti/Mg atomic ratio in alloys. As the Ti/Mg atomic ratio increased the alloy charge transfer resistances decreased probably due to the partial selective dissolution of the surface Ti/Ti-oxides and thus the limited enrichment of the surface by the electro-catalytic Ni. The average hydrogen diffusion coefficients in all the Ti-including alloys were higher than that in MgNi alloy. The increase in Ti/Mg atomic ratio, however, did not cause any further increase in the average hydrogen diffusion coefficient.