Oxygen and nitrogen co-doped porous carbon nanosheets derived from Perilla frutescens for high volumetric performance supercapacitors

Biomass-derived carbon materials with structural diversities and their applications in energy storage

“…In addition, the biomass-derived carbon materials with 2D sheets have been prepared by carbonized leaf [34,[90][91][92], stalk [25,93], nutshell [94], waste coffee grounds [95], okara [96], eggplant [97], silk [98], fish scale [99], biomass-based molecules (chitosan [100] and gelatin [35]), etc. These biomass precursors themselves have a multiple layer structure or cause a new structural rearrangement to form 2D sheets during the pyrolysis.…”

“…For example, Yang et al [96] reported a N-doped carbon sheets derived from okara with a high nitrogen content of 9.89 at%. Other biomass derived carbons, such as wheat flour [136], stem bark [58], MOB [127], tobacco rods [125], perilla frutescens [34], pine needle [103], had 1 at% nitrogen. In order to increase the nitrogen content of biomass-derived carbon materials, some nitrogen-containing dopants (NH 4 Cl [109], (NH 4 ) 2 SO 4 [137], NH 3 [138], urea [114], melamine [139]) were introduced.…”

“…Because N doping can enhance the electronic conductivity and wettability, while O, B, S or P-doping can provide the pseudo-capacitance, enlarge the carbon interlayer distance and increase additional active sites, N, O co-doping [34,122,123,129,138], N, B co-doping [35,147], N, S codoping [81,92,146,148] and N, P co-doping [39,99,149] have been designed to further improve the electrochemical performances of biomass-derived carbon materials. For instance, Sun et al [147] reported a separated N, B co-doped porous graphitic carbon from nitrogencontaining chitosan through coordinating boric acid and Fe catalyst, and followed by ZnCl 2 -activation process.…”

“…All the characteristics strongly suggest that biomass-derived carbon could be qualified for the electrode of supercapacitors. To date, various biomass-derived carbon materials with high SSA, abundant pore structure and modified functional groups have been prepared, such as the stems [87,102,157,[177][178][179], leaves [34,90,101,103,126], seeds [48,77,79,154], fructus [180][181][182], pericarp [88,89] of plants, nut shells [94,143,[183][184][185], fungi [53,109,[186][187][188], abandoned food [96,131,189], shellfish [49,72,133], animal tissue [112,115,124], polysaccharide [44,85,147,155,190], protein [137].…”

“…On the other hand, the defects including vacancies, edges and heteroatoms can be formed during the biomass pyrolysis process [31]. Most natural biomass materials contain nitrogen and/or sulfur, which can be doped by heteroatoms, resulting in increasing electric conductivity and extra active sites [34,35]. More importantly, a large amount of biomass material is recycled from the daily or agricultural wastes, meaning an effective, cheap and environment-friendly process of the electrode materials.…”