Heat treatment of iron/carbon composites for energy storage: effect on physicochemical and electrochemical properties

Abstract

Carbon materials are widely used as supercapacitor electrodes while iron oxides and other iron compounds are promising electrode materials due to its pseudocapacitive contribution. This work deals with the preparation and electrochemical characterization of iron/carbon composites for supercapacitor electrode applications. The carbon precursor samples were prepared from a carbonization of babassu coconut endocarp, and the iron/carbon nanocomposites were obtained by precipitation synthesis using iron salt, followed by a heat treatment at different temperatures. The electrochemical characterization of the samples show that, at low current density, the sample without iron compounds shows the higher electrical capacitance, up to 98 F g-1 in 2 M H2SO4. This good performance can be associated to a pseudocapacitive contribution of the oxygenated functional groups present in this sample. However, at higher current densities, the best electrochemical behaviour was achieved for the sample treated at 1000 °C. This good performance is may be associated to the Feº and Fe3C nanoparticles present in the sample which can enhance its electrical conductivity. On the other hand, is no there clearly evidence of pseudocapacitive contribution of the iron particles. Future works will seek to improve the surface area of the materials with the aim to increase the double layer capacitance, and also to perform electrochemical studies using other electrolytes.