The effect of MWNTs with different diameters on the electrochemical hydrogen storage capability

The difference in electrochemical hydrogen storage of pure multi-walled carbon nanotubes (MWNTs) with different diameters of 10-20 nm, 10-30 nm, 20-40 nm, 40-60 nm and 60-100 nm were investigated. The MWNTs were synthesized by chemical vapor deposition (CVD) using LaNi5 alloy particles as catalyst and were treated in vacuum at 600 degrees C. Three-electrode system was introduced. The CNTs-Ni electrodes were used as the working electrode, which were prepared by mixing carbon nanotubes (CNTs) and Ni powder in a weight ratio of I : 9 and compressing the mixture into porous nickel collector. 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. 10-30 nm CNTs has the best electrochemical hydrogen storage capacity with a highest capacity of 480.6 mAh/g and a corresponding discharging plateau voltage of 0.95 V, which were gained at 200 cycle with 200 mA/g charge/discharge current density. However, 60-100 nm CNTs has the lowest capacity of 298.3 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. (c) 2005 Elsevier B.V. All rights reserved.