The study of the electrochemical properties of CNTs–LaNi5 electrodes

The effect of MWNTs with different diameters on the electrochemical properties of LaNi5 alloy were investigated. The MWNTs were synthesized by chemical vapor deposition (CVD). The purified CNTs were treated with a temperature of 500 °C for 1.5 h in vacuum. Three-electrode system was introduced. The CNTs–LaNi5 electrodes were used as the working electrode, which were prepared by mixing carbon nanotubes (CNTs) and LaNi5 Alloy in a weight ratio of 1:10. Ni(OH)2/NiOOH worked as the counter electrode and Hg/HgO as the reference electrode. 6 mol/L KOH solution acted as the electrolyte. Results showed that MWNTs with different diameters represented a great discrepancy in the electrochemical hydrogen storage capability under the same testing condition. The CNTs–LaNi5 electrodes in which CNTs diameter is 20–40 nm has the best electrochemical hydrogen storage capacity with a highest capacity of 425.9 mAh/g and a corresponding discharging plateau voltage of 1.07 V, which were gained with 200 mA/g charge current density and 60 mA/g discharge current density 0.2 V discharge voltage limit. However, 60–100 nm CNTs–LaNi5 electrodes has the lowest capacity of 340.5 mAh/g under the same testing condition. This shows that the tube diameter of CNTs is an important factor that influences its electrochemical hydrogen storage performance.