Microwave post-treated activated carbons for capacitance boosted non-aqueous supercapacitors

Herein, as a novel idea, a microwave (MW) post-treatment strategy is proposed to modify the structure and surface characteristics of already prepared activated carbons (ACs) for application in non-aqueous Electric Double-Layer Capacitors. Pistachio nutshell-derived carbon is first KOH-activated and then subjected to MW irradiation for 0, 2, 5, and 10 minutes. X-ray Diffraction and Raman analyses show that MW post-treatment leads to structural modifications, and FTIR and XPS analyses reveal relative elimination of surface functional groups which results in subsequent enhancement in water contact angle and renders more favorable surface wetting of carbon by non-aqueous organic electrolyte. The performance characteristics of symmetrical non-aqueous supercapacitors incorporated with the prepared ACs show a significant positive effect of MW irradiation in such a way that 0 and 10-minute-irradiated ACs demonstrate 152 and 392 F g-1 capacities, respectively, at 1.75 A g-1, with the corresponding specific energies and powers of 340 Wh kg-1 and 11 kW kg-1 for AC-10, respectively. This remarkable enhancement in the electrochemical performance is attributed to the effective role of the MW post-treatment in modifying the AC structure as well as providing AC surfaces that have better wettability with less polar non-aqueous electrolyte. Moreover, this strategy is additionally applicable to make hydrophobic activated carbons for other applications as the absorption of less polar contaminants from liquid or gaseous environments.