Developing potential aqueous Na-ion capacitors of Al2O3 with carbon composites as electrode material: Recycling medical waste to sustainable energy

Energy has become an unavoidable part of our day-to-day life; it can be generated from renewable sources of energy, avoiding the depletion of fossil fuels. Electrochemical energy stored is the most efficient and clean form of energy. The choice of electrode material plays a crucial role in the performance of batteries and supercapacitors. The energy storage devices can be made more sustainable and cost-effective if derived from waste. Rising demand of vaccines in this pandemic eon has accumulated the wastes, which need to be recycled promptly to avoid environmental pollution. In this study, the dumped vaccine-bottle caps which are made up of aluminum have been recovered successfully by leaching method, also in order to enhance the performance of the generated residue, it was supported by carbon to improve the conductivity of the derived metal oxides. The physical and electrochemical properties of the synthesized materials were analyzed by various advanced technologies. The re-synthesized Al2O3/C particles have been applied as electrode in Na2SO4 electrolyte for supercapacitor application. The Al2O3/C electrode delivered a specific capacity of 147 C g−1 in Na2SO4 at a current density of 1 A g−1. The Na-ion capacitor was fabricated with Al2O3/C and vulcan carbon (VC) electrodes then the device performance was optimized. A wide potential window of 2 V with good long-term stability was achieved for the aqueous Na-ion capacitor in 1 M Na2SO4 electrolyte. The device was found to deliver an energy density of 21 W h kg−1 at a power density of 8064 W kg−1. Thus, recycling and reuse of Al2O3/C electrode in Na-ion capacitor application can be incalculable step towards ecofriendly, cost-effective energy storage systems, additionally it also pave way to recycling other waste like used mask or covers.