High-performance supercapacitors based on MoS2, TiO2, ZnO, and CQD nanocomposites: a comparative study

Supercapacitors are emerging as promising candidates for sustainable and high-performance energy storage; however, their efficiency is strongly governed by the properties of electrode materials, particularly their conductivity, surface area, and electrochemical activity. In this work, carbon quantum dots (CQDs) were synthesized using a green and sustainable hydrothermal method, employing banana peels as a low-cost carbon precursor. The obtained CQDs were incorporated to enhance the electrochemical properties of MoS₂-based binary and ternary composites, namely MoS₂–BN, MoS₂–TiO₂, and MoS₂–BN–ZnO. These CQD-integrated composites were mixed with carbon black (CB) and polyvinylidene fluoride (PVDF) and uniformly deposited onto nickel (Ni) foam substrates to fabricate high-performance supercapacitor electrodes: MoS₂–BN@CQDs, MoS₂–TiO₂@CQDs, and MoS₂–BN–ZnO@CQDs. Among them, the MoS₂–TiO₂@CQDs electrode exhibited the most superior electrochemical performance in a three-electrode configuration, achieving a specific capacitance (C_s) of 474 F/g, an energy density (E_d) of 29.03 Wh/kg, and a power density (P_d) of 62.99 W/kg at 0.1 A/g, along with outstanding cycling stability over 7500 charge–discharge cycles. These findings highlight the potential of CQD-engineered MoS₂ and TiO₂-based hybrids for next-generation high energy storage devices, paving the way for their integration into practical and scalable supercapacitor applications.