Chemical Activation for Supercapacitor Electrodes Materials for Energy Storage: Synthesis and SEM Characterization

Abstract

Activated carbon derived from coconut shells is a widely used porous material with diverse applications. In this study, activated carbon suitable for supercapacitor electrodes was prepared by chemical activation process using potassium hydroxide (KOH) as an activating agent. Coconut shell was used as the raw material and was carbonized/ activated at 700 0C for varying activation times of 1hr, 2hrs and 3hrs for the three samples respectively. From the activated carbon produced, it has been observed that a greater yield was obtained from sample A, activated/carbonized for the duration of 1 hour. Also it has being observed that the stainless steel cup produced carbon faster on heating at low temperature. The porous structure of activated carbon was characterized by some techniques such as scanning electron microscopy (SEM), Energy Dispersive Spectroscopy (EDS) in order to investigate the porosity, surface morphology and chemical composition of the activated carbon produced. The pores obtained were analyzed using Zeiss Image Analyzer. The largest pore diameter was obtained in sample C (activated/carbonized for 3hrs) having average pore diameter as Daverage = 315.4 nm. The results obtained from EDS shows that high concentration of carbon (71.25% by weight) was found in sample C (activated/carbonized for the duration of 3 hrs). The weight percentage of carbon in the activated carbon produced is in the range of 62.81% to 71.25% and the impurities left are from 29.75% to 38.29%. This implies that the longer the duration of activation/carbonization time, the higher the quality (concentration) of carbon in the activated carbon. The activated carbon produced is inferred to have high electric capacity and stable electric characteristics due to high macroporosity of the activated carbon produced. Further investigation using Brunauer-Emmett-Teller (BET) surface area analysis will elucidate the impact of these characteristics on the electrochemical performance of the electrodes in supercapacitors.

Keywords: Activated carbon, chemical activation, supercapacitor electrode, carbonization, macroporocity.