Synthesis of N/P/S Co-Doped 3D Cross-Linked Carbon Nanosheets by Double Activation Method for High-Performance Supercapacitors

Graphical SUPERcaps : N/P/S co-doped carbon nanosheets (NPS-CNs) were synthesized by acid-free and alkali-free strategy from pyrene for supercapacitors, achieving a high-rate capability (201.2 F g −1 at 100 A g −1 ) and high cycle stability (93.4 % of initial capacitance after 30000 cycles). It is still a challenge to prepare heteroatoms-doped carbon materials for supercapacitors by an acid-free and alkali-free synthesis method. Herein, the N/P/S co-doped carbon nanosheets (NPS-CNs) were synthesized by an in-situ K 2 CO 3 and Na 2 S 2 O 3 ⋅ 5H 2 O double activation method from pyrene as carbon source, melamine-phytic acid supramolecular aggregate as N and P source without the presence of acid and alkali. The as-prepared NPS-CN featured three-dimensional cross-linked nanosheets with abundant pores, boosting the stability of carbon skeleton and promoting the transfer of ion and electron. The abundant micropores together with high heteroatom content (15.09 %) provided abundant active sites and defects for ion adsorption. Benefitting from these merits, the NPS-CN electrode exhibits a high specific capacitance of 485.1 F g −1 at 0.05 A g −1 as well as good rate performance of 350.3 F g −1 at 20 A g −1 in three electrode system. Simultaneously, the specific capacitance of the NPS-CN capacitor reached 305.0 F g −1 at 0.05 A g −1 and retained 201.2 F g −1 at 100 A g −1 in two electrode system. Importantly, NPS-CN capacitor presented an excellent cycle stability (93.4 % of initial capacitance after 30,000 charge/discharge cycles). This work opened a less harmful route to prepare NPS-CNs from small polycyclic aromatic hydrocarbons for energy storage devices.