Carbon quantum Dot incorporated Xanthan gum based gel polymer electrolytes for high performance supercapacitors

In this study, a novel biodegradable gel polymer electrolyte (GPE) was developed using carbon quantum dots (CQDs)-infused xanthan gum (XG) as the polymer matrix, sodium perchlorate (NaClO₄) as the ionic dopant, and glycerol as the plasticizer. The GPE was paired with activated carbon (AC) and graphene (GC) electrodes to fabricate symmetric supercapacitor cells to enhance energy storage performance. Xanthan gum underwent hydrothermal treatment to form a distinctive puffer ball-like microstructure, which was further nucleated into CQDs. This study introduced an innovative approach by incorporating carbon quantum dots into a polymer electrolyte system, with a new focus on investigating the interactions between the polymer matrix and the salt, offering new insights into their integrated performance. These CQDs functioned as stabilizers and enhanced both the ionic conductivity and electrochemical behavior of the GPE. Structural and morphological analyses, including X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM), confirmed a wave-like, porous surface and well-dispersed CQDs. Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) revealed strong intermolecular interactions among the GPE constituents, indicating excellent thermal and chemical stability. Electrochemical studies showed that the AC electrode achieved a specific capacitance of 92 F g⁻¹ via cyclic voltammetry (CV), while the GC electrode delivered 69 F g⁻¹. Galvanostatic charge-discharge (GCD) tests at 1 mA g⁻¹ showed that the GC electrode reached specific capacitance of 75 F g⁻¹, with energy density and power density of 10.40 Wh kg⁻¹ and 0.49 kW kg⁻¹ respectively. Similarly, AC electrode-based supercapacitor was tested which showed specific capacitance, energy density and power density as 45 F g⁻¹, 5.55 Wh kg⁻¹, and 0.66 kW kg⁻¹, respectively. Both systems demonstrated good reversibility and cycling stability, highlighting the potential of CQD-integrated biodegradable GPEs and carbon-based electrodes for environmentally friendly, flexible, and high-performance supercapacitor applications.