2-anilino-1,4-naphthoquinone and 2-benzylamino-1,4-naphthoquinone with activated carbon composite electrodes for supercapacitor application

This study focuses on the synthesis and electrochemical characterization of two naphthoquinone derivatives, 2-anilino-1,4-naphthoquinone (ANQ) and 2-benzylamino-1,4-naphthoquinone (BNQ), as promising composite materials with activated carbon (AC) for supercapacitor applications. Current supercapacitor electrodes use AC as the active material; however, the specific capacitance is limited by its surface area due to its electric double layer capacitive behavior. ANQ and BNQ were employed as composite material with AC to resolve this issue using pseudocapacitive behavior, which combines surface and chemical redox behavior for increased capacitance. First, ANQ and BNQ were analyzed using various techniques, including nuclear magnetic resonance spectroscopy, Fourier transform infrared spectroscopy, and electrospray ionization mass spectroscopy, to confirm their molecular structures. Then, the composite electrodes AC-ANQ and AC-BNQ were thoroughly investigated through scanning electron microscopy, energy-dispersive X-ray spectroscopy, and Brunauer–Emmett–Teller analysis to understand their surface morphology, elemental composition, and porosity. Notably, at an AC:NQ derivative weight ratio of 3:1, ANQ and BNQ efficiently occupied AC pores, a vital factor in achieving superior electrochemical performance. Finally, electrochemical characterization, including cyclic voltammetry, electrochemical impedance spectroscopy, and galvanostatic charge-discharge testing, demonstrated promising results for ANQ-AC and BNQ-AC composite electrodes with high specific capacitances of 134 and 174 F g−1, respectively. Additionally, these composite electrodes exhibited exceptional cycle stability over 10,000 cycles at high current densities. The enhanced electrochemical results are attributed to the pseudocapacitive behavior of quinone derivatives. ANQ and BNQ in particular have an extra aromatic ring attached to the naphthoquinone molecule which allows for additional π-π van der Waals stacking interactions between ANQ and BNQ, and AC which is theorized to be the reason for the excellent cycling stability. Our findings show the promise of ANQ and BNQ as composite materials with AC for enhancing supercapacitor electrode performance.