Enhancing specific capacitance and cycling stability of zinc oxide-based supercapacitors using gamma-irradiated, amine-passivated carbon dots

Due to an energy crisis, the development of low-cost, high-performance supercapacitors is of great interest. This paper describes for the first time the use of gamma-irradiated, amine-passivated carbon dots to improve the ZnO-based supercapacitor performance. The carbon dots were irradiated by gamma ray at 50 kGy (CDs-EDA-50) and 200 kGy (CDs-EDA-200) in the presence of ethylenediamine (EDA). Compared to the pure ZnO electrode, the ZnO-CDs-EDA-50 and ZnO-CDs-EDA-200 electrodes boosted the specific capacitance by 194% and 312%, respectively. In addition to the specific capacitance, the cycling stability was also improved from 87.41% to 99.87% after 8500 cycles. Through several electrochemical analyses and contact angle measurement, the modified carbon dots in the composite electrodes were found to enhance several key factors, including surface-controlled capacitance, series resistance, ion diffusion coefficient, electrochemical active surface area, wettability, and mechanical integrity of the electrode, resulting in higher specific capacitance and cycling stability. This work demonstrates that the use of gamma-irradiated, amine-passivated carbon dots as electrode additives has potential for ZnO-based supercapacitors and can be applied for the fabrication of other high-performance energy storage devices. [Display omitted] •The gamma-irradiated, amine-passivated carbon dots were prepared.•The modified carbon dots/ZnO composites were employed in supercapacitors.•The specific capacitance was improved by 312%.•Cycling stability was also improved from 87.41% to 99.87% after 8500 cycles.•Several key factors were enhanced by the modified carbon dots.