Chitosan-Based Synthesis of O, N, and P Codoped Hierarchical Porous Carbon as Electrode Materials for Supercapacitors

Abstract

Reasonable porous structure and proper heteroatom doping have great influences on electrode materials for supercapacitors. Herein, O, N, and P codoped hierarchical porous carbon (ONPC) was synthesized through a one-pot carbonization−activation strategy by using chitosan as the carbon precursor, phosphoric acid as the activator, and melamine foam as the skeleton. The use of melamine foam facilitated the formation of an interconnected carbon framework and introduced more nitrogen functional groups. Owing to the hierarchical pore structure, large surface area (1588 m 2 g −1 ), and significant heteroatom contents of O (8.61%), N (7.95%), and P (1.34%) in the carbon matrix, the 700 °C carbonized sample ONPC-700 had a specific capacitance of 230 F g −1 at 0.2 A g −1 . A high energy density of 7.5 Wh kg −1 at 100 W kg −1 was achieved for the supercapacitor fabricated with two identical ONPC-700 electrodes. Furthermore, the capacitance retention of the device was evaluated to be as high as 86.53% after 8000 cycles.

Dual‐template synthesis of hierarchical porous carbon and its application in electrical double‐layer capacitors

“…It can be seen from Figure 5A that the CV curves of the HPCs exhibit a quasi-rectangular shape with a scanning rate of 5 mV/s, revealing the electrical double-layer capacitive behaviour. [8,24,43] The enclosed area of the CV curve represents the specific capacitance of the HPCs, and thus the HPC-2 is supposed to possess the highest specific capacitance. [19,44] The CV curves of the HPC-2 still retain the profile of a roughly quasi-rectangular shape at a relative high scanning rate of 200 mV/s (Figure 5B), indicating a remarkable rapid electrochemical response.…”

“…[51] The intercept of the Nyquist plot on the axis of Z´reveals the equivalent series resistance (R s ), including the intrinsic resistance of the material, the electrolyte resistance, and the contact resistance at the electrode-electrolyte interface. [8,52] As shown in Figure 6B, the R s values of HPC-x (x = 1, 2, and 3) are estimated to be 0.51, 0.46, and 0.48 Ω, respectively. Low R s is beneficial to enhance the rate capability of the electrode, and thus HPC-2 has the highest capacitance retention rate among the tested samples.…”

“…The phase HPCMgK-600 922 6 M KOH 225.3@ 1 A/g 88 Chen et al [4] ONPC-700 1588 6 M KOH 230@0.2 A/g 86. 5 Yi et al [8] HPC 2-4.5 3343 6 M KOH 277@0.05 A/g 95.1 Pan et al [9] HPC-1 1171 6 M KOH 249.2@0.5 A/g 80.2…”

“…The electrode material is considered the key component of the EDLCs, which determines the ultimate electrochemical performance, such as specific capacitance and power density. [ 8,9 ]…”

“…The electrode material is considered the key component of the EDLCs, which determines the ultimate electrochemical performance, such as specific capacitance and power density. [8,9] Until now, activated carbon is still the most widely used electrode material for EDLCs due to its high specific surface area, developed pore structure, stable chemical properties, and relatively low price. [10,11] To improve the electrical double-layer capacitance of EDLCs, electrode materials are required to have an optimized structural design, a high surface area, a reasonable pore size distribution, and enough active sites for electrostatic adsorption.…”