We present here a simple strategy to achieve high energy density capacitor by functionalizing zeolite-templated carbon (ZTC), which is a nanographene-based material having a very high specific surface area (&gt;3600 m2/g) together with a uniform pore size (1.2 nm) and ordered micropore structure, with quinone molecules by wet impregnation method. Two types of quinone, anthraquinone (AQ) and tetrachlorohydroquinone (TCHQ), which have different redox potential, were introduced into ZTC framework and were electrochemically characterized in a sulfuric acid electrolyte. We have found that the amount of quinones loaded into ZTC can be increased up to 60 wt% (6AQ-4ZTC and 6TCHQ-4ZTC), where the capacity of the functionalized electrodes reach their maximum resulting from the quinones adsorbed inside the nanochannels of ZTC. This loading amount is two-fold higher than that of the activated carbon (Maxsorb) recently reported. Beyond this value, quinones would form larger crystals (as confirmed by XRD analysis) adsorbed at the external surface of the ZTC particles. These indicate that a large amount of the quinones, AQ and TCHQ, can be introduced into the ZTC framework and adsorbed inside its 1.2-nm pore. Cyclic voltammograms of 6AQ-4ZTC and 6TCHQ-4ZTC confirms the redox peaks corresponding to the redox reaction of AQ and of TCHQ, respectively. We have simply calculated that inside one supercage of ZTC, which has a diameter of 1.2 nm, approximately 3-4 of quinones (AQ and TCHQ) can be adsorbed. H-NMR analyses (not shown here) reveal that these quinone molecules in a nanopores of ZTC would had a less-ordered structure, which agree well with the results from XRD measurements indicating the less-crystalline or nanocrystalline of the quinones. A redox capacitor using a couple of quinone-doped ZTC electrode (with the loading amount of 60 wt%) was then assembled and characterized in the sulfuric acid electrolyte. The quinone/ hydroquinone couple consists of AQ and TCHQ as the active materials with different redox potentials for proton insertion/ extraction reactions, in which protons in the electrolyte will play a role of charge carrier and are shuttled back and forth between two electrodes (so called a proton rocking-chair system). The assembled hybrid capacitor exhibits a high energy density (30.6 Wh kg-1), with an operating voltage of 1.4 V, which is superior to the activated carbon-based capacitors working in an organic electrolyte.

Hybrid redox capacitor with high energy density derived from quinone-functionalized zeolite templated-carbon

249th National Meeting (2015)

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