Cooking carbon with protic salt: Nitrogen and sulfur self-doped porous carbon nanosheets for supercapacitors

We develop a novel self- doped and self- template strategy to synthesize N, S doped porous carbon nanosheets (N/S- HCSs) by pre- carbonization and post- activation of a low- cost protic salt of p- phenylenediamine toluenesulfate ([pPD][2CH(3)PhSO(3)]). [pPD][2CH(3)PhSO(3)] is obtained by a simple neutralization reaction at room temperature and behaves as an "all- in- one" precursor, serving as C, N, S sources and a self- template. As- prepared N/S-HCSs possess large specific surface area and nanosheet geometry which provide enough adsorbing sites for charge accumulation and shorten diffusion distance of electrolyte ions at electrode/electrolyte interface. Besides, N/S-HCSs exhibit unique porous nanoarchitecture with uniform ultramicropores and a well- developed network of supermicropores and mesopores, which guarantees highly efficient ion- highways for electrolyte diffusion and transport. Furthermore, incorporated heteroatoms in the carbon framework structure improve the electrical conductivity and surface wettability, and provide extra pseudocapacitance. As a result, N/S-HCS electrode delivers superior electrochemical performance including high gravimetric capacitance (280 F g(-1) at 1.0 A g(-1)), good rate performance (134F g(-1) at 50 A g(-1)) and cycling stability (94.4% retention after 10,000 cycles at 2.0 A g(-1)) in 6M KOH electrolyte. The present innovative synthetic concept can be easily implemented, without