Abstract: The structure change of carbon nanotubes (CNTs) after heat treatment and the effect of CNTs treated at different temperatures in nitrogen ambient on the electrochemical properties of CNTs-LaNi5 electrodes were investigated. The thickness of CNTs after heat treatment is thinner, the number of layers is less and the outside diameter is smaller than those unheated of CNTs. So the deposition and release of hydrogen are easier. CNTs-LaNi5 electrodes were prepared by mixing CNTs and LaNi5 alloy in a mass ratio of 1:10. The CNTs-LaNi5 electrodes with CNTs treated at 800 ℃ in nitrogen has the best electrochemical hydrogen storage capacity with a highest capacity of 519.1 mAh•g-1 and a corresponding discharging plateau voltage of 1.19 V. From 500 ℃ to 800 ℃, the higher the temperature of the heat treatment is, the better the electrochemical hydrogen storage property of the electrode will be. However, CNTs-LaNi5 electrodes with CNTs treated at 900 ℃ has a lower capacity. This shows that the temperature of treatment is an important factor that influences electrochemical hydrogen storage performance of CNTs. Pure LaNi5 electrode has a discharge capacity of only 265.6 mAh•g-1 and a discharging plateau voltage of only 0.83 V, which are lower than those of all CNTs-LaNi5 electrodes treated at different temperatures in nitrogen ambient.

Key words: Carbon nanotubes, Electrochemical properties, Hydrogen storage alloy, Heat treatment