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 electro-chemical 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 super-capacitor during the charging/discharging process. As a result, the NHPC-1 electrode in the supercapacitor exhibits a high specific capacitance of 231 Fg(-1) at 1 Ag-1 and superior retention of 98% after 5000 cycles at 1 Ag-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.