A Study of Hydrogen Accumulation in Multiwall Carbon Nanotubes by Electrochemical Techniques

Abstract

Accumulation of electrolytic hydrogen in alkaline medium (5 M KOH) by multiwall carbon nanotubes (MWCNTs) 20–60 nm in inner diameter and 2 μm in length obtained by catalytic pyrolysis of propane/butane mixture has been studied by means of the electrochemical diffusion technique, cyclic voltammetry, and impedance spectroscopy. MWCNTs were applied on a steel membrane and were encapsulated by a 10-nm electrolytic nickel layer. Cyclic voltammograms were recorded in the range of potentials from −1.2 to +0.2 V and contained a current peak in the cathode region corresponding to hydrogen absorption by nanotubes at −0.9 V and current peak in the anode region corresponding to oxidation of absorbed hydrogen at −0.6 V. Hydrogen storage capacity of MWCNTs varies from 4.6 to 6.5% depending on the amount of nanotubes according to electrochemical diffusion data. The electrochemical impedance data correlate with the results of the above methods.