A multifunctional potassium peroxodisulfate activation strategy to construction of N, S co-doped carbon nanosheets for high-performance Zn-ion hybrid supercapacitors

Exploration of non-corrosive chemical activation agents that are capable of transforming sustainable biomass into nanocarbon with large specific surface area and suitable heteroatomic content for electrochemical energy storage applications is highly desired. Herein, potassium peroxodisulfate (K2S2O8) has been proposed as the effective activation agent for the synthesis of N, S co-doped carbon nanosheets (N, S-CNSs) from renewable onions. Different from the other activation agents, it was found that the K2S2O8 can act as the physical activating agent and chemical activating agent simultaneously owing to its temperature-dependent decomposition behavior. Consequently, the N, S-CNSs with large specific surface area of 2110.6 \({\mathrm{m}}^{2}{\mathrm{g}}^{-1}\), optimal oxygen, nitrogen, and sulfur-containing functional groups were rationally emerged. The assembled Zn-ion hybrid supercapacitors with the as-prepared N, S-CNSs delivered a maximum specific capacity of 141.5 mAh \({\mathrm{g}}^{-1}\), robust cycling stability with 98.3% capacity retention after 20,000 cycles, and large specific energy up to 113.4 Wh k \({\mathrm{g}}^{-1}\). As explicitly discussed with the relevant characterizations, the study deeply explored the adaptability of the chemical activating agent in general synthesis of porous carbon-based materials from sustainable biomass, and great insight for designing high-performance electrochemical energy storage devices.