Electrochemical Oxidation of Anthracene to Anthraquinone inside the Nanopores of Activated Carbon: Implications for Electrochemical Capacitors

Anthracene (ANT) is oxidized to anthraquinone (AQ) insidethe nanoporesof activated carbon (AC) without any metal catalysts. The resultinghybrid of AC and AQ shows high performance as an anode for aqueouselectrochemical capacitors due to the reversible redox reaction ofAQ inside the nanopores of AC. ANT is first adsorbed inside the nanoporesof AC in the gas phase and finely dispersed at the nanolevel. Consequently,the adsorbed ANT has a large contact area with the conductive carbonpore surface. The adsorbed ANT is then electrochemically oxidizedto AQ in aqueous H2SO4 electrolyte. The oxidationof ANT requires conductive surfaces for charge transfer, and ANT isefficiently oxidized at the large contact interface between the conductivecarbon pore surface and ANT by using AC. The hybrid is capable offast charging and discharging through rapid charge transfer at thelarge contact interface. In addition, since the hybridization of AQinside the AC pores does not expand the volume of AC particles, thevolumetric capacitance is enhanced by the hybridization. Furthermore,the nanopores of AC prevent AQ from desorbing into the electrolyteduring charging and discharging. Consequently, the hybridization endowsthe hybrid with a high volumetric capacitance, a high rate capability,and a long cycle lifetime. We demonstrate that nanopores can providethe reaction environment not only for efficient oxidation of ANT asnanoreactors but also for a fast redox reaction of AQ.