Efficient synthesis of nitrogen and oxygen co-doped hierarchical porous carbons derived from soybean meal for high-performance supercapacitors

Abstract

Adopting an impregnation strategy, the homogeneous and efficient pore-creating are simultaneously achieved by one-pot KOH activation making full use of the swelling feature of hydrophilic soybean protein gels in alkaline solution. N, O co-doped porous carbons (NOPCs) have been fabricated using soybean meal as carbon, nitrogen and oxygen sources for an abundance of protein with a smaller amount of corrosive KOH. The as-obtained NOPCs exhibit advantageous characteristics for electrochemical energy storage including unique honeycomb-like morphology with interconnected carbon frameworks, high specific surface area, hierarchical porosity and controllable surface chemistry, which provides a large number of favorable nanochannels with suitable surface property for fast electrolyte diffusion and efficient electron transfer in the carbon networks. When tested as supercapacitor electrodes with symmetric configuration in 3 M KOH electrolyte, the NOPC-700 electrode prepared at 700 °C with a KOH/soybean meal mass ratio of 0.25 presents a high specific capacitance (330 F g−1 at 0.5 A g−1), remarkable cycling stability (94.6% capacitance retention after 10000 cycles at 2.5 A g−1), and superior rate capability (270 F g−1 at 5 A g−1). Furthermore, the NOPC-700//NOPC-700 supercapacitor delivers a maximum energy density of 8.4 Wh kg−1. The coordination between protein-rich soybean meal and one-pot KOH activation plays an important role in efficiently synthesizing porous carbons with robust energy storage performance for supercapacitors.