Two-Dimensional Carbon Nanosheets for High-Performance Supercapacitors: Large-Scale Synthesis and Codoping with Nitrogen and Phosphorus

Abstract

Two-dimensional carbon nanosheets codoped with N and P species have been successfully synthesized by a template carbonization method coupled with nitrogenization and phosphorylation processes using trisodium citrate dihydrate, melamine, and NH 4 H 2 PO 4 as C, N, and P sources, respectively. Dopants of N and P species play crucial roles in the determination of carbon porosities and electrochemical performance; notably, increasing the P content can lead to a decrease in the BET surface area together with a corresponding decrease in the electrochemical performance. For instance, regulating the mass ratio between the C source and the N and P sources to 2:1 results in the maximum BET surface area of 1340 m 2 g −1 , whereas a ratio of 1:2 results in a decreased value of only 47 m 2 g −1 . Moreover, the mass ratio of 1:1 results in superior electrochemical behaviors, with a maximum energy density that can reach up to 13.3 Wh kg −1 . The present synthesis method provides an alternative route for producing N-and P-containing carbon nanostructures with two-dimensional features, serving as excellent electrode materials for energy propagation and storage.

Nitrogen and Sulfur Self-Doped Activated Carbon Directly Derived from Elm Flower for High-Performance Supercapacitors

“…Columbic efficiency was also calculated on the basis of the ratio of discharge/charge time. 52 − 54 As shown in Figure S2 , the as-obtained N,S-ELAC- x samples displayed higher efficiency. The specific capacitance of the three KOH-activated samples (calculated using eq 1 ) at six current densities ranging from 1 to 20 A g –1 is illustrated in Figure 5 d. At 1 A g –1 , N,S-ELAC-2 provided a capacitance of 275 F g –1 .…”

“…The higher discharge time of N,S-ELAC-2 compared to that of either N,S-ELAC-1 or N,S-ELAC-3 indicates that N,S-ELAC-2 has a relatively higher specific capacitance. Columbic efficiency was also calculated on the basis of the ratio of discharge/charge time. − As shown in Figure S2, the as-obtained N,S-ELAC- x samples displayed higher efficiency. The specific capacitance of the three KOH-activated samples (calculated using eq ) at six current densities ranging from 1 to 20 A g –1 is illustrated in Figure d.…”

Urea‐Modified Phenol‐Formaldehyde Resins for the Template‐Assisted Synthesis of Nitrogen‐Doped Carbon Nanosheets as Electrode Material for Supercapacitors

“…Carbon nanosheets having typically porous features, compared traditional porous carbon materials, have shown many scientific advantages of faster ion/electron transfer, shorter ion/electron transport/diffusion length, which are very likely to serve as supercapacitor electrode materials ,. However, capacity of carbon‐based supercapacitor primarily from the electric double layer capacitor (EDLC) is relatively low largely restricting its real application .…”

N/P Codoped Porous Carbon/One-Dimensional Hollow Tubular Carbon Heterojunction from Biomass Inherent Structure for Supercapacitors

“…Supercapacitors hold great promise in scientific research, due to their high power density, ultrafast charge/discharge rate, superior stability, long cycle life, and safe operation. − Carbonaceous materials play essential parts in this field, some of which could be put down to the advisible chemical composition and diversiform microtexture features. − In this context, heteroatom (e.g., N, P, B, and S) doping has been proven to be a promising method to remarkably improve the electrochemical performance. The electronic structure, atomic radius, and electronegativity of heteroatoms are different from those of carbon atoms, which not only introduce energy defect sites on the surface of material, but also modulate the electron donor–acceptor characteristics. ,− Thus, the N/P codoped carbon materials have been investigated to obtain higher electrochemical properties through improving the wettability in the electrolyte, increasing the electrical conductivity, introducing mixed pseudocapacitance, and widening the potential window. ,− Furthermore, the carbon materials with one-dimensional (1D) hollow structure, such as carbon fibers and carbon microtubes, not only ensure adequate contact area between the active sites and the electrolyte but also possess an efficient pathway for ion and electron transport, thus obtaining excellent-performance supercapacitors. − Taking the above things into account, it is greatly advisible to construct N and P codoped 1D hollow carbon materials as supercapacitor electrode materials.…”