Macromolecular Polyethynylbenzonitrile Precursor-Based Porous Covalent Triazine Frameworks for Superior High-Rate High-Energy Supercapacitors

Abstract

Porous covalent triazine framework (CTF)-based carbon materials have gained increasing attention in energy-storage applications because of their tunable structure, high chemical stability, and rich heteroatom contents. However, CTFs have thus far been exclusively synthesized from small-molecular precursors and generally show unsatisfactory supercapacitive performance. We report herein the construction of a novel range of CTFs of significantly improved supercapacitive performance from polyethynylbenzonitrile (PEBN) as a unique macromolecular precursor for the first time by ionothermal synthesis. CTF-800 synthesized at the optimized condition (800 °C; ZnCl2/PEBN mass ratio of 3:1) shows a nanosheet-like morphology with a high yield (∼90%), high nitrogen content (>5.8%), high specific surface area (1954 m2 g–1), and optimized micropore to meso/macropore surface area ratio (42:58). As the electrode material for supercapacitor application, CTF-800 exhibits a high specific capacitance of 628 F g–1 at 0.5 A g–1, high-rate performance (71% of capacitance retention at 50 A g–1), and excellent cyclic stability (96% of capacitance retention over 20 000 cycles) in a three-electrode system with aqueous 1 M H2SO4 electrolyte. Symmetric supercapacitor devices have been further fabricated with CTF-800 in aqueous 1 M H2SO4, [EMIM]­[BF4], and LiPF6 electrolytes separately. The device with the aqueous electrolyte shows the highest capacitance of 448 F g–1 (at 0.5 A g–1) and a high energy density of 15.5 W h kg–1. The devices with [EMIM]­[BF4] and LiPF6 electrolytes exhibit exceptional energy densities of 70 and 78 W h kg–1, respectively, and retain energy densities of 41 and 45 W h kg–1, respectively, even at the high power density of 15 000 W kg–1, confirming their high-rate high-energy performance. Meanwhile, the device with [EMIM]­[BF4] electrolyte has also been demonstrated to operate well at various temperatures ranging from −20 to 60 °C with remarkable energy-storage performance.

Ultrastable Covalent Triazine Organic Framework Based on Anthracene Moiety as Platform for High-Performance Carbon Dioxide Adsorption and Supercapacitors

“…CTFs have been used in heterogeneous catalysis, gas storage, CO 2 absorption and conversion, and sensing, as well as electrocatalysis for oxygen reduction reactions, potential electrodes in lithium batteries, supercapacitors, and other energy storage systems [ 45 , 46 , 47 , 48 , 49 , 50 ]. Vadiyar et al reported a polyethynylbenzonitrile-based CTFs with high specific surface area, higher capacity retention (71%), and high capacitance up to 628 F·g −1 at 50 A·g −1 [ 51 ]. Li et al successfully synthesized nitrogen-enriched tetracyanoquinodimethane-derived conductive CTFs (TCNQ-CTFs), which also exhibited very good specific capacity (380 F·g −1 ), high energy density (42.8 W·h·kg −1 ), and extraordinary cycling performance up to 10,000 cycles without compromising the loss of capacity [ 52 ].…”

O/N Co‐Doped, Layered Porous Carbon with Mesoporosity up to 99 % for Ultrahigh‐Rate Capability Supercapacitors

“…Recently, covalent triazine-based frameworks (CTFs) have emerged as an attractive precursor for the fabrication of such mesoporous carbons. [43][44][45] Owing to the covalent attachment of rigid aromatic building blocks, these N-enriched CTFs can meet the requirements of high SSA along with narrowly distributed micropores. [43,44] Besides, CTFs can be facilely synthesized by ZnCl 2 triggered cyclotrimerization of carbonitrile monomers and their properties such as porosity, SSA, and N-or other heteroatom-contents can also be finely tuned by monomer design.…”

“…[43,44] Besides, CTFs can be facilely synthesized by ZnCl 2 triggered cyclotrimerization of carbonitrile monomers and their properties such as porosity, SSA, and N-or other heteroatom-contents can also be finely tuned by monomer design. [45,46] Herein, we report the fabrication of O/N-co-doped mesoporous carbon by one-step Na 2 CO 3 activation of CTF precursor that derived from 2,4,6-tris(4-cyanophenoxy)-1,3,5-triazine monomer (namely CTFO). The CTFO precursor synthesized by ZnCl 2 -mediated ionothermal trimerization possessed a relatively high SSA of 851 m 2 g À 1 along with a pore-size distribution of 0.5-3 nm.…”

“…If those precursors can be activated in such a manner that only causes the pores to become enlarged, but without producing additional micropores through the selection of activation agents (i. e., weakly corrosive Na 2 CO 3 ), mesoporous carbons with high percentage of mesopore volume together with well‐defined mesopores can be fabricated in this way. Recently, covalent triazine‐based frameworks (CTFs) have emerged as an attractive precursor for the fabrication of such mesoporous carbons . Owing to the covalent attachment of rigid aromatic building blocks, these N‐enriched CTFs can meet the requirements of high SSA along with narrowly distributed micropores .…”

Layer-by-Layer Electrode Fabrication for Improved Performance of Porous Polyimide-Based Supercapacitors

“…In addition, the contribution of acetylene black could be recognised in both scenarios in terms of EDLC, with a more prominent involvement expected in the traditional SC. Additionally, the presence of a sizeable π-conjugated system could further facilitate the electrical conductivity and hence increase the Li + ion adsorption to the active material [ 40 , 41 ]. Secondly, the pronounced pseudocapacitive contribution in the layered SC CVs indicates surface faradic redox reactions of Li + ions with carbonyl functionalities of the perylene diimide-based polymers ( Scheme 2 ).…”