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Biomass‐derived carbon materials are an amazing electrode material for supercapacitor, owing to their abundant, porous structure and composition. Herein, a controllable N content carbon material with hierarchical porous structure was fabricated via an integrated carbonization, activation and nitrogen‐doping process. N‐rich camellia pollen is used as carbon precursor, while NH4Cl is employed as both activation agent and dopant. The optimal N‐doped carbon with higher N content (3.82 at%), suitable pore size distribution and larger specific surface area (810 m2 g−1), provides abundant ion transport channels and exposes more accessible active sites. Thus, a high specific capacitance of 280 F g−1 (1 A g−1) in 6 M KOH (three‐electrode system) can be obtained with making full use of N−HPC‐1. Moreover, the assembled symmetrical supercapacitor delivers high energy densities both in 6 M KOH (13.3 Wh kg−1) and 1 M Na2SO4 (20 Wh kg−1) that can be used for LED lighting. More than that, it is also demonstrates excellent cycle stability in 6 M KOH (85.4% after 20000 cycles at 20 A g−1). In view of the above‐mentioned merits, this N‐doped hierarchical porous carbon is anticipated to be a promising material for application in supercapacitors and other fields. [ABSTRACT FROM AUTHOR]

Multi-element doped porous carbon materials are considered as one of the most promising electrode materials for supercapacitors due to their large specific surface area, abundant mesoporous structure, heteroatom doping and good conductivity. Herein, we propose a very simple and effective strategy to prepare nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) by one-step pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. The optimized N-S-HPC-2 possesses a typical hierarchically porous framework (micropores, mesopores and macropores) with a large specific surface area (1284.87 m2 g − 1) and N (4.63 atomic %), S (0.53 atomic %) doping. As a result, the N-S-HPC-2 exhibits excellent charge storage capacity with a high gravimetric capacitance of 360 F g − 1 (1  A g − 1) in three-electrode systems and 178 F g − 1 in two-electrode system and long-term cycling life with 87% retention after 10,000 cycles in KOH electrolyte. Nitrogen, sulfur co-doped hierarchical porous carbons (N-S-HPC) materials are prepared by a very simple and effective pyrolysis strategy. The effect of sole dopants as a precursor was a major factor in the transformation process. This work demonstrates that K2CO3 and thiourea synergistic effect can greatly enhance electrochemical properties of the heteroatoms co-doped biomass based hierarchically porous carbon. [ABSTRACT FROM AUTHOR]

Heteroatoms-doped biomass-derived carbon materials (HBC), a new task and hotspot of the current energy research, especially supercapacitor, have featured with low cost and rich sources with enhanced physical, chemical and electrical properties compared with those of pure counterparts. Nevertheless, converting the biomass into high-performance carbon materials by green chemical activators and dopants is still imperatively needed. Herein, a simple and cost-effective one-step method was proposed, using different nitrogen-containing compounds (NH 4 Cl, (NH 4) 2 CO 3 and urea) as both activation agent and dopant, to prepare nitrogen-doped biomass-derived hierarchical porous carbon materials (HPCs). The effect of nitrogen-containing compounds on the electrochemical performance of HPCs was also studied. Among them, NH 4 Cl is proved to be the porogen with the minimum collapse of pollen grain and urea can be identified as the most effective N dopant. Furthermore, the prepared HPC-urea (HPC-U) electrode deliver the highest specific capacitance of 300 F g−1 at 1 A g−1 and rate performance of 50% from 1 to 50 A g−1 in three electrode system, while HPC-NH 4 Cl possesses the maximum capacitance retention rate of 95.2% after 10,000 cycles. In addition, HPC-U based SCs exhibits the highest energy density (14.3 Wh kg−1). Notably this work may provide a certain guideline for choosing N dopants and porogens to prepare biomass-derived carbon materials for the target application. [Display omitted] • An integrated carbonization, activation and doping process for hierarchical porous carbon. • Heteroatoms-rich camellia pollen is used as carbon precursor. • Three nitrogenous compounds is utilized as both activation agent and dopant. • NH 4 Cl is proved to be the porogen with minimum collapse of pollen grain. • Urea can be identified as the most effective N dopant. [ABSTRACT FROM AUTHOR]