Chemical foaming-assisted synthesis of N, O co-doped hierarchical porous carbon from soybean protein for high rate performance supercapacitors

The conversion of biomass into porous carbon materials with hierarchical porosity and rich heteroatom doping is vital for supercapacitors. However, it is still challenging to efficiently synthesize high-capacitance porous carbon materials with optimized porosity. Herein, N, O co-doped hierarchical porous carbon materials with good rate performance were obtained from Zn(NO3)2·6H2O and soybean protein by a facile one-step chemical foaming process. Zn(NO3)2·6H2O not only functioned as the foaming agent, but also acted as the precursor of hard templates and activation agent. The influence of Zn(NO3)2·6H2O content and carbonization temperature on the microstructure and capacitance performance of the resulting carbonaceous products were investigated. The optimized sample exhibited the largest specific surface area of 1350 m2 g−1 and Vt of 1.01 cm3 g−1. The specific capacitance could reach 248 F g−1 at 0.5 A g−1 and retain 109 F g−1at 100 A g−1. The symmetrical supercapacitors exhibited a maximum energy density of 15.75 Wh kg−1 which could light LED bulbs with a voltage of 3 V and power an electronic watch for more than 35 min demonstrating their potential applications. This work paves a shortcut to the synthesis of high rate performance hierarchical porous carbon materials with a low cost and multifunctional chemical foaming agent. The strategy is worth promoting to other biomass in producing hierarchical porous carbon materials for various energy storage devices.