A novel strategy to prepare N, S-codoped porous carbons derived from barley with high surface area for supercapacitors

In this work, barley derived N, S-codoped porous carbons are synthesized through a simple, one-step chemical activation method using copper citrate as an activating agent. The copyrolysis of barley and copper citrate contributes to the formation of numerous micro-/mesopores and high surface area. Owing to redox reactions between copper citrate and carbon matrix during the activation process, the as-prepared porous carbon possesses a ultrahigh specific surface area of 2139.6 m(2) g(-1), hierarchical porous architecture with a large pore volume of 1.16 cm(3) g(-1), and high nitrogen, oxygen and sulfur contents. The resultant carbon material with high porosity and appropriate heteroatom doping exhibits a high specific capacitance of 401.6F g(-1) at 0.5 A g(-1) in a 6.0 M KOH electrolyte and good rate capability with the capacitance remaining 165.6F g(-1) at 100 A g(-1). Additionally, the assembled symmetric carbon-based supercapacitor delivers a high energy density of 30.9 Wh kg(-1) and superior long-term cycling stability of 94.8% capacitance retention after 20,000 cycles in 1.0 M Na2SO4 electrolyte. This work provides a facile strategy to design high-surface-area porous carbons with adjustable pore structure and rich heteroatom amount, which holds a promising future for constructing high energy carbon-based supercapacitors.