Nitrogen-doped hierarchical porous carbon for supercapacitors with high rate performance

Nitrogen-doped, hierarchical porous carbons with high surface area are synthesized using sucrose as carbon precursors, and nitrogen-containing organic salt, i.e. ethylenediamine tetraacetic acid disodium zinc salt (EDTANa(2)Zn), as hard template, activation agent and nitrogen source simultaneously. During pyrolysis of the EDTANa(2)Zn/sucrose composites, the nano-ZnO and Na2CO3 particles produced from EDTANa(2)Zn are evenly dispersed in the nitrogen-doped carbon, which can act as hard templates to create mesopores. Furthermore, the nano-ZnO can etch carbon as an activation agent when the pyrolysis temperature further increases. The carbon thermal reduction reaction and the subsequent evaporation of the Zn form many micropores and small mesopores. Due to the hierarchical porous architecture, large surface area (2160 m(2) g(-1)) and nitrogen doping, the carbon prepared at 950 degrees C exhibits a high specific capacitance (229 F g(-1) at 0.1 A g(-1)), excellent rate capability (191 F g(-1) at 300 A g(-1)) and superior cycle durability (capacitance retention of 95.3% after 20,000 cycles at 10 A g(-1)) in 6 M KOH aqueous electrolytes, showing promise as an outstanding supercapacitor electrode material.