Schiff-Base/Resin Copolymer under Hypersaline Condition to High-Level N‑Doped Porous Carbon Nanosheets for Supercapacitors

We develop a novel strategy to fabricate nitrogen-rich porous carbon nanosheets (N-PCNs) using Schiff-base/resin copolymer under hypersaline medium. Melamine-terephthalaldehyde Schiff-base containning high-bond-energy C=N covalent bonds effectively reduces the loss of the N species during carbonization and thus provides high nitrogen dopants, while the introduction of melamine-formaldehyde resin and ZnCl2 as a solubility enhancing stabilizer plays a key synergistic effect in making the formation of stable polymeric network. Besides, ZnCl2 also serves as a salt-templating and a foaming agent. The resultant N-PCNs have a rich N-doping of 6.55 wt %, a unique nanosheet morphology with a thickness of ∼200 nm, and a large surface area of 1403 m2 g–1 along with rational porous architecture, which affords superior electrochemical performances for a supercapacitor electrode such as high gravimetric capacitances of 362 and 268 F g–1 at 2.0 A g–1 in a three-electrode and a two-electrode system, respectively, using KOH electrolyte. Moreover, the electrode delivers remarkable energy density of 9.2 Wh kg–1 at the power density of 505 W kg–1 and a high cycling stability with 93.8% capacitance retention at 1.0 A g–1 after 10 000 cycles. The present study provides a new avenue for facile and high efficient construction of N-enriched porous carbons for potential supercapacitor application.