Towards the Mechanism of Electrochemical Hydrogen Storage in Nanostructured Carbon Materials

P. S. FERNÁNDEZ; E. B. CASTRO; S. G. REAL; M E MARTINS

Foz do Iguaçú

Congreso; ISE 2008 Spring Meeting of the International Society of Electrochemistry; 2008

International Society of Electrochemistry

Carbon nanotubes (CNTs) combine unique chemical and physical properties which have attracted the interest of numerous researchers for applications such as supercapacitors, chemical sensors and energy storage devices. One of the most exciting application fields for CNTs is hydrogen storage. The storage of hydrogen in a light element like carbon could lead to the formation of power supplies for mobile applications with higher energy densities. Dillon et al. reported for the first time excellent hydrogen storage properties of single walled carbon nanotubes (SWNTs). Thereafter, many research groups started to carry out hydrogen storage experiments. Most of the studies on hydrogen storage in CNTs were conducted by temperature-programmable desorption measurements and electrochemical methods. From the literature results it is quite difficult to reach a common conclusion for maximum adsorption capacity. The variation of hydrogen storage capacity may arise due to the differences of CNTs used (SWNT or multi walled carbon nanotubes), purity, chirality of tubes, tube diameter, bundle appearance and possible presence of metals used as catalysts in the synthesis procedure. Furthermore, metals able to interact with hydrogen can also be introduced during the activation process. Besides the debate of hydrogen storage capacity, there are other important tasks to be achieved such as the understanding of the mechanism for hydrogen storage. The aim of this work is to study the electrochemical absorption and desorption of hydrogen in SWNTs. The hydrogen sorption ability has been evaluated electrochemically in a three-electrode cell in an aqueous 6M KOH medium, where activated and purified SWNT is used as the working electrode, nickel is the counter electrode and Hg/HgO/6M KOH is the reference electrode (+0.098V vs NHE).