Application of nanotextured carbons for electrochemical energy storage in aqueous medium

Abstract

This paper presents a hybrid capacitor, with two different electrodes working in their optimal potential range. The negative electrode is based on the reversible hydrogen sorption which occurs at low potential values in nanoporous carbons. Galvanostatic cycling at temperatures ranging from 20 to 60°C demonstrates that hydrogen is weakly chemisorbed. This is confirmed by TPD on the electrode material after charging, which shows a peak due to hydrogen at 200-250°C. The positive electrode is a composite made of carbon nanotubes, as minor component, and MnO2. Interesting properties are given by the presence of nanotubes, such as a developed porosity, a high electrical conductivity and a good resiliency, all being very important for enhancing the power and cycle life of supercapacitors. The hybrid capacitor is able to operate at voltage values as high as 2 V in aqueous medium with a long cycle life. ©2006 Sociedade Brasileira de Química.