Nitrogen‐Doped Hierarchical Porous Carbon Framework Derived from Waste Pig Nails for High‐Performance Supercapacitors

In situ nitrogen‐doped hierarchical porous carbon was synthesized by using waste protein‐rich pig nails as precursors in a facile KOH activation method. The microstructure and electrochemical characteristics of the materials were investigated by tuning the amount of KOH. When the weight ratio of KOH to pig nails is 1 : 1, the obtained nitrogen‐doped hierarchical porous carbon (NHPC‐1) exhibits the largest specific surface area (2569 m 2 g −1 ) with interconnected porous network structure, which are beneficial to ion/electron storage and transfer. In addition, abundant nitrogen of 2.8 at % in the NHPC‐1 also contributes to the high electrochemical activity of the supercapacitor during the charging/discharging process. As a result, the NHPC‐1 electrode in the supercapacitor exhibits a high specific capacitance of 231 F g −1 at 1 A g −1 and superior retention of 98 % after 5000 cycles at 1 A g −1 in 6 M KOH electrolyte. Additionally, the assembled symmetric device based on NHPC‐1 exhibits a high energy density of 7 Wh kg −1 at a power density of 500 W kg −1 . Our study suggests that waste pig nails can act as low‐cost and renewable carbon precursors for high performance supercapacitor.