Room-temperature synthesis of ZnO-based quantum dots for enhanced electron/ion transport in ultra-stable hybrid supercapacitors

In this study, ZnO-based quantum dots (QDs) were synthesized at room temperature, which exhibited remarkable electrochemical performance. A bandgap reduction from 4.24 to 3.13 eV enhances electron/ion movement from the valence band to the conduction band by reducing the energy barrier, increasing electron mobility, and facilitating faster and more efficient charge storage. Furthermore, it improves stability by minimizing the potential for thermal degradation. The bandgap reduction was also confirmed via first-principles studies. The ZnO-based QDs achieved a specific capacitance of 1961 F g⁻¹ at 1 A g⁻¹ with ultra-high cycling stability, retaining 99 % of their capacitance after 100,000 galvanic charge-discharge cycles. A hybrid supercapacitor (ZnO-QDs@NF//AC@NF) achieved a maximum energy density of 39.58 W h kg⁻¹ and a power density of 7431 W kg⁻¹. Additionally, a specific capacitance of 118 F g⁻¹ at 1 A g⁻¹ was achieved by maintaining 94.34 % of its original capacitance after 100,000 cycles. These findings highlight the capability of this hybrid supercapacitor for advanced energy-storage applications owing to significant improvements in its electrochemical characteristics.