Green synthesis of sodium pyrithione salt-activated biomass-derived carbon for aqueous zinc-ion capacitors†

Conversion of biomass into doped activated carbons (ACs) via green processes is envisioned as a promising path toward modern energy storage applications. ACs are commonly synthesized using strong bases, which are associated with environment and operation risks. Thus, it is necessary to find alternative and green activation reagents. Herein, we report a multi-functional molecular salt (sodium pyrithione) as an activation reagent for the economically viable preparation of doped ACs with a large surface area, rich dopants, and porous structures. The formation of carbons and the variation in the composition and pore architecture were demonstrated. The prepared ACs were then fabricated into cathodes for a zinc-ion capacitor. We correlated the properties of ACs with their performance by analyzing electrochemical measurements. Meanwhile, the optimal SPHC-based ZIC delivered high capacity and excellent cycling stability over 20 000 cycles under practical conditions. Moreover, we found that long-term chemical adsorption/desorption on active sites of ACs influences the cathode structure and thus leads to a loss of capacity and changes in the energy storage mechanism. Overall, this work provides an alternative protocol for the synthesis of doped ACs, which can be used as cathodes materials for practical high-performance ZICs.