The study of the electrochemical properties of CNTs–LaNi 5 electrodes

Abstract

The effect of MWNTs with different diameters on the electrochemical properties of LaNi 5 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–LaNi 5 electrodes were used as the working electrode, which were prepared by mixing carbon nanotubes (CNTs) and LaNi 5 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–LaNi 5 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–LaNi 5 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.