Phenylenediamine‐Derived Carbon Dots for Carbon‐Based Supercapacitors

In the present investigation, multicolor fluorescent carbon dots (CDs) are produced using meta (m‐PD), ortho (o‐PD), and para (p‐PD) phenylenediamine isomers as precursors. These CDs display bright and stable green, yellow, and red fluorescence under ultraviolet light excitation, with variations in photoluminescence emissions attributed to differences in particle size and bandgap. The CDs from o‐PD, m‐PD, and p‐PD are thoroughly characterized using techniques such as UV–vis spectroscopy, fluorescence emission spectroscopy, transmission electron microscopy, a zeta sizer, Fourier Transform Infrared Spectroscopy, and Raman spectroscopy. As electrode materials in a two‐electrode system for symmetric supercapacitors, the performance of CDs is examined, revealing that m‐PD‐derived CDs (m‐CDs) exhibit superior electrochemical properties. Specifically, m‐CDs achieve a specific capacitance of 72.3 F g−1 at 0.1 A g−1, an energy density of 1.00 Wh kg−1, and a power density of 9.41 kW kg−1. The enhanced performance of m‐CDs is attributed to an increase in electropositivity and faster electron mobility associated with smaller particle sizes. This research highlights the potential of utilizing PD‐derived CDs to enhance the electrochemical performance of supercapacitors, demonstrating significant advancements in energy storage technology.