Indigo-Functionalized Activated Carbon Electrode for Screen-Printed Eco-Friendly Supercapacitors

Employing indigo to functionalize commercial activated carbon (CAC) for screen-printed electrodes represents an innovative approach to enhance the electrochemical characteristics of CAC, making it suitable for applications in supercapacitors (SCs). The indigofunctionalized activated carbon (IAC) electrode material was successfully synthesized through a solvothermal method. Various material characterization techniques, such as X-ray diffraction, thermogravimetric analysis, BET surface area analysis and Raman spectroscopy confirmed the successful functionalization of indigo onto the CAC. Screen-printed SCs fabricated with aqueous electrolyte exhibit a specific capacitance of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$32.7 \mathrm{F} \mathrm{g}^{-1}$</tex> at a current density of <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$0.5 \mathrm{A} \mathrm{g}^{-1}$</tex> which is higher than the CAC (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$10.8 \mathrm{F} \mathrm{g}^{-1}$</tex>). This work presents a promising pathway for developing printed, sustainable, and non-toxic SCs for low power wireless sensors and IoT devices.