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.
Doping carbon materials with heteroatoms such as N, F is an effective approach to elevating the capacitive performance of supercapacitors. In this paper, nitrogen and fluorine dual-doped two-dimensional (2D) porous carbon nanosheets (PCNSs) have been fabricated by a straightforward template carbonization method, using trisodium citrate as carbon source and self-template, and ammonium fluoride as N/F dopants. The N/F-doped carbon samples are well characterized by a series of techniques and measured in a three-electrode system and two-electrode system, respectively. As a result, N/F-doped carbon has delivered large capacitance of 110[Formula: see text]F[Formula: see text]g[Formula: see text] at 1[Formula: see text]A[Formula: see text]g[Formula: see text] and high-energy density of 3.82[Formula: see text]W h kg[Formula: see text] at the power density of 0.5[Formula: see text]kW[Formula: see text]kg[Formula: see text]. It is also revealed that semi-ionic C–F bonds in PCNSs have enhanced electrical conductivity, hence, facilitating electron transport in the electrode. For comparison, ammonium chloride is used as sole dopant for producing N-doped carbon materials, whose capacitive performances are much lower than the N/F-codoped one, indicating the synergistic effect of N/F for capacitive improvement.
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