Comparison between Electrochemical Capacitors Based on NaOH- and KOH-Activated Carbons

Abstract

This work describes the chemical activation of a coke using two different activating agents in order to investigate their behaviour as electrodes in supercapacitors. A coke was chemically activated with two hydroxides (KOH and NaOH) under nitrogen flow, at a constant mass hydroxide/coke ratio of 2 and temperatures of 600, 650 and 700 ºC. All the samples were characterized in terms of porosity by N 2 sorption at 77 K, surface chemistry by temperature programmed desorption (TPD) and electrical conductivity. Their electrochemical behaviour as electric double layer capacitors was determined using galvanostatic, voltammetric and impedance spectroscopy techniques, in an aqueous medium with 1M H 2 SO 4 as electrolyte. Large differences in capacitive behaviour with the increase in current density were found between the two series of activated samples. The different trends were correlated with the results obtained from the TPD analysis of the CO-type oxygen groups. It was found that these oxygen groups make a positive contribution to capacitance finding a good correlation between the specific capacitance values and the amount of these oxygen groups was found for both series.

Energy storage applications of activated carbons: supercapacitors and hydrogen storage

“…96 Bleda-Martínez et al found also a good correlation between the specic capacitance of activated carbons and the amount of surface oxygen groups desorbing as CO. 48 Many other reports on pseudocapacitance contribution of oxygengroups in activated carbons are available. [188][189][190][191][192][193][194] Oxidation treatments, both chemical (HNO 3 or H 2 SO 4 ) and electrochemical, have also been applied to activated carbons to generate oxygen-containing functionalities, increasing the specic capacitance of the material. [195][196][197][198][199] Additionally, Mysyk et al have shown that a high concentration of oxygenated surface functionalities can prevent further oxidation of the activated carbon, allowing operation in a wider potential window.…”

Investigation on Template Etching Process of SBA‐15 Derived Ordered Mesoporous Carbon on Electrocatalytic Oxygen Reduction Reaction

“…It is well known that the morphology of the OMC (including specific surface area, pore size and volume) can be altered by post‐synthesis modification. In industries, KOH activation is a common method usually employed to generate micropores in activated carbon ,. The activation conditions such as temperature, concentration and other to facilitate the merging of micropores to get mesopores.…”

Pomelo peel-derived lamellar carbon with surface oxygen functional groups for high-performance supercapacitors

“…According to the literature, the pseudocapacitive effect is described by the following reaction (Eq. 1) [32].…”