Electrochemical behaviour of single walled carbon nanotubes – Hydrogen storage and hydrogen evolution reaction

The electrochemical behaviour of single walled carbon nanotubes (SWCNT) related to the mechanism involved in the hydrogen electrode reaction applying electrochemical and spectroscopic techniques is studied. Cyclic voltammetry applied to electrodes containing different percentages of SWCNT demonstrates that this material can behave as efficient capacitor and that the hydrogen electrode reaction develops through the H-electrosorption followed by the formation of molecular H₂ and its evolution. Also, SWCNT are able to storage hydrogen within their porous structure. This is confirmed through the galvanostatic charge and discharge experiments. Electrochemical impedance spectroscopy allowed calculating the real area that takes part in the electrode reaction and the main and valuable conclusion is that the hydrogen electrode reaction consists of a simple charge transfer reaction and that the H adatom relaxation or diffusion processes can be disregarded. Furthermore, a model proposed for their structure which was validated through impedance experiments confirms those conclusions. Results of Raman spectra allowed identifying the nature of the electrodes confirming that after purification the material is composed of single walled carbon nanotubes.