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

Abstract 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.