Mohr's salt assisted KOH activation strategy to customize S-doped hierarchical carbon frameworks enabling satisfactory rate performance of supercapacitors

Highlights: • Mohr's salt assisted KOH activation strategy has been developed for the synthesis of S-doped carbon frameworks. • Both of Mohr's salt and KOH play multiple roles during the synthesizing process. • The resulting carbons have large specific surface area and moderate mesopore content. • The resulting supercapacitors have satisfactory rate performance in both aqueous electrolyte and ionic liquid electrolyte. -- Abstract: The construction of heteroatom-doped hierarchical carbon frameworks has attracted significant research attention as high-performance electrode materials for supercapacitors. Herein, a facile one-step Mohr's salt-assisted KOH activation strategy has been developed for the production of S-doped hierarchical carbon frameworks with large specific surface area from sustainable spruce bark. We found Mohr's salt plays multiple roles during the synthesizing process by simultaneously acting as an S source, the template to generate mesopores, and the co-activator beyond KOH. As the electrode for supercapacitors, the high specific capacitance of 281 and 156 F g⁻¹ can be achieved in aqueous electrolyte and ionic liquid electrolyte at 1 Ag⁻¹, respectively. More importantly, the electrode also displays excellent rate capability where a high capacitance can be maintained at large charge-discharge operation. Moreover, the supercapacitor device also demonstrated an energy density is high up to 66.26 Wh kg⁻¹ at the power density of 875 W kg⁻¹ in ionic liquid electrolyte. These results acquired could offer a versatile way to convert renewable biomass into value-add porous carbon for electrochemical energy-storage applications.