“Frying” milk powder by molten salt to prepare nitrogen-doped hierarchical porous carbon for high performance supercapacitor

Abstract

A simple method similar to frying was used to pyrolysis of renewable biomass carbon milk powder in NaCl/Na2CO3 molten salt at 700 °C under the air atmosphere to prepare nitrogen-doped hierarchical porous carbon. This preparation method displayed a simple preparation process with the low requirements for equipment and low-cost raw materials. The prepared optimal nitrogen-doped porous carbon material exhibited a hierarchical porous with macropores, mesopores, and micropores and had a high specific surface area of 1095 m2 g−1. As supercapacitors electrodes, The prepared optimal sample displayed a high specific capacitance of 391.5 F g−1 at 0.5 A g−1 and an excellent rate performance. It also exhibited excellent cycle stability (only loss of 4.4% capacitance) at 4 A g−1 over 5000 cycles. Moreover, In a symmetrical two-electrode system of 1 M Na2SO4, the assembled supercapacitor displayed a high energy density of 33.0 Wh kg−1 at 0.25 A g−1, maintained a high energy density of 22.3 Wh kg−1 at 20 A g−1 and exhibited excellent stability at 5 A g−1 over 5000 cycles. The assembled symmetrical PVA/Na2SO4 solid supercapacitor can successfully light up the light emitting diode (LED). This work provided a sample and low consumption way to prepare N doped hierarchical porous carbon electrode material for high performance supercapacitors.