Beyond Conventional Activating Methods, a Green Approach for the Synthesis of Biocarbon and Its Supercapacitor Electrode Performance

The development of cost-effective and renewable carbon electrodes by using a green production approach is of significant importance for supercapacitors (SCs). Herein, we present an effective synthetic method that utilizes pistachio shells and Na 2 S 2 O 3 as a carbon precursor and activating agent, respectively, to prepare porous carbon by hydrothermal carbonization and subsequent chemical activating processes. The NCNaK-1 (optimum sample, N/S doped carbon prepared by Na 2 S 2 O 3 and KCl at 800 °C) exhibits sponge-like morphology, a relatively high specific surface area of 775 m 2 g –1 along with interconnected hierarchical porosity, and high nitrogen/sulfur doping into the carbon framework. The specific capacity of the NCNaK-1 electrode is as high as 166 F g –1 at a current density of 0.5 A g –1 in 1 M KOH electrolyte and ∼96% capacitance retention over 5000 cycles. Moreover, a SC assembled with NCNaK-1 electrodes has an energy density of 2.7 W h kg –1 at a power density of 250 W kg –1 . This research introduces a sustainable, environmentally benign, economic, high production yield, and efficient porous carbon production strategy.