High Rate Performance Supercapacitors Based on N, O Co-Doped Hierarchical Porous Carbon Foams Synthesized via Chemical Blowing and Dual Templates.

N, O Co-Doped porous carbon materials are promising electrode materials for supercapacitors. However, it is still a challenge to prepare high capacitance performance N, O Co-Doped porous carbon materials with balanced pore structure. In this work, a simple chemical blowing method was developed to produce hierarchal porous carbon materials with Zn(NO 3 ) 2 ·6H 2 O and Fe(NO 3 ) 3 ·9H 2 O as the foaming agents and precursors of dual templates. Soybean protein isolate served as a self-doping carbon source. The amount of Fe(NO 3 ) 3 ·9H 2 O influenced the microstructure, element content and capacitance performance of the obtained porous carbon materials. The optimized sample CZnFe-5 with the addition of 5% Fe(NO 3 ) 3 ·9H 2 O displayed the best capacitance performance. The specific capacitance reached 271 F g -1 at 0.2 A g -1 and retained 133 F g -1 at 100 A g -1 . The CZnFe-5//CZnFe-5 symmetric supercapacitors delivered a maximum energy density of 16.83 Wh kg -1 and good stability with capacitance retention of 86.33% after 40,000 cycles tests at 50 A g -1 . The symmetric supercapacitors exhibited potential applications in lighting LED bulbs with a voltage of 3 V. This work provides a new strategy for the synthesis of hierarchical porous carbon materials for supercapacitors from low-cost biomass products.