Organic salt-derived nitrogen-rich,hierarchical porous carbon for ultrafast supercapacitors

Longfeng Hu, Li Ma, Qizhen Zhu, Lanyong Yu, Qi Wu, Chen Hu, Ning Qiao and Bin Xu*

Nitrogen-rich, hierarchical porous carbons with high surface area were simply prepared by direct pyrolysis of a nitrogen-containing organic salt, i.e. ethylenediaminetetraacetic acid calcium disodium salt (EDTANa₂Ca), as electrode materials for supercapacitors. Besides micropores originating from the elimination of some **all molecular substances, the template effects of nano-CaO and nano-Na₂CO₃ particles (the intermediate products derived from EDTANa₂Ca) created some meso/macropores, resulting in a developed hierarchical porous structure. As the pyrolysis temperature increases from 600 °C to 850 °C, the nitrogen content decreases from 10.8 at% to 1.48 at%, whereas both the BET surface area and the pore volume increase dramatically. The BET surface area and pore volume of the carbon prepared at 850 °C reach as high as 2015 m² g⁻¹ and 1.74 cm³ g⁻¹, respectively, and the meso/macropores account for about 70% of the total pore volume. The developed hierarchical porous structure enables the carbon to exhibit excellent rate capability. It can endure an ultrafast scan rate of 5000 mV s⁻¹ and an ultrahigh charge/discharge current up to 200 A g⁻¹ with a capacitance of 115 F g⁻¹ in 6 mol L⁻¹ KOH.