CO 2 outperforms KOH as an activator for high-rate supercapacitors in aqueous electrolyte - Université de Lorraine Access content directly
Journal Articles Renewable and Sustainable Energy Reviews Year : 2022

CO 2 outperforms KOH as an activator for high-rate supercapacitors in aqueous electrolyte

J. Castro-Gutiérrez
R.L.S. Canevesi
M. Emo
A. Celzard
Vanessa Fierro
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Abstract

Although high-surface area activated carbons used as supercapacitor (SC) electrodes are frequently produced by KOH activation, this study shows that, when aqueous electrolytes are used, CO2 activation is a better choice from the point of view of SC performance, environment and economy. Ordered mesoporous carbons (OMCs) produced by a mechanochemical synthesis method from mimosa tannin are activated with KOH to use these materials as electrodes for SCs. A comparative analysis of the same OMCs but activated with CO2 is presented to examine the effect of the activation process on materials performance. KOH-activated materials exhibit good electrochemical performance at low charging rates, reaching specific cell capacitance values of 49 F g-1 at 0.5 A g-1, however, restricted access to microporosity and low water affinity water reduces their performance at high charging rates. In contrast, the best performing CO2-activated material can retain 81 % of capacitance at 20 A g-1, compared to 25 % for a KOH-activated OMC with similar properties and tested under the same conditions. A thorough review of the open literature suggests that CO2 activation would produce materials with a suitable combination of pore network connectivity and water affinity, resulting in SCs with high rate capability in an aqueous electrolyte. These conclusions were drawn by judiciously integrating the analysis of: (i) the hysteresis loop scanning of N2 adsorption-desorption isotherms; and (ii) water adsorption isotherms as tools to more accurately assess the pore network connectivity and water affinity of the materials, which are not generally considered when studying SC performance.
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Dates and versions

hal-03840590 , version 1 (05-11-2022)

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Attribution - NonCommercial - NoDerivatives

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J. Castro-Gutiérrez, R.L.S. Canevesi, M. Emo, M.T. Izquierdo, A. Celzard, et al.. CO 2 outperforms KOH as an activator for high-rate supercapacitors in aqueous electrolyte. Renewable and Sustainable Energy Reviews, 2022, 167, pp.112716. ⟨10.1016/j.rser.2022.112716⟩. ⟨hal-03840590⟩
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