One-step production of N, S co-doped honeycomb-like activated carbon from instant dry yeast for high gravimetric and volumetric performance supercapacitors

Abstract

Recently, honeycomb-like activated carbons with open porous structure and high specific surface area (SSA) have been intensively explored in supercapacitors and exhibit excellent gravimetric performances. But their relatively low volumetric capacitance and energy density in supercapacitors are unfavorable for applying in future energy storage devices. Herein, N,S co-doped honeycomb-like activated carbons (NSHAC) are produced from instant dry yeast by one-step NaOH activation method. The SSA, pore volume, pore size, heteroatoms content and electrochemical performance of NSHAC are directly determined by the activation temperature. The optimized NSHAC-700 has a high SSA of 818 m2 g−1, a high density of 1.02 g cm−3, hierarchical pore structure with the micoporosity of 89.2 % and rich surface heteroatoms (2.2 % at for N and at 1.3 % for S). Importantly, NSHAC-700 overcomes the drawbacks of presently honeycomb-like activated carbons and exhibits ultra-high gravimetric capacitance (492 F g−1) and volumetric capacitance (502 F cm−3) in 6 M KOH in a three-electrode system. Furthermore, very high gravimetric energy density of 10.9 W h kg−1 and volumetric energy density of 11.1 W h L−1 have been achieved by the symmetric NSHAC-700 based supercapacitors in 6 M KOH. This one-step NaOH activation method provides a sustainable way of preparing N, S co-doped honeycomb-like activated carbon for next-generation high-performance supercapacitors.