Enhanced electrochemical performance of S,N-containing carbon materials derived from covalent triazine-based frameworks with a tetrathiafulvalene core

Abstract

To address the challenges posed by a growing population, limited resources, and demands of modern lifestyles, energy research is of prime importance. In this context, we have used 2,3,6,7-tetra(4-cyanophenyl)tetrathiafulvalene (TTFCN), a redox-active building block, to fabricate a pair of covalent triazine-based frameworks (CTFs), named CTFTTF@1-400 and CTFTTF@2-400 (where 1 = ZnCl₂ : monomer (5 : 1); 2 = ZnCl₂ : monomer (10 : 1)) under Lewis acidic (ZnCl₂) conditions at 400 °C for supercapacitor applications. To enhance the supercapacitor performance of CTFs, we have carried out the synthesis at 700 °C, resulting in the formation of the S,N-containing carbon material CTFTTF@2-700. Nitrogen sorption isotherms (77 K) revealed BET surface areas of 330, 650 and 1350 m² g⁻¹ for CTFTTF@1-400, CTFTTF@2-400, and CTFTTF@2-700, respectively, with different micropore to mesopore ratios. These porous materials when used as electrodes, specifically CTFTTF@2-700 exhibited an excellent electrochemical performance with the highest specific capacitance of 943 F g⁻¹ at 1 A g⁻¹ and 708 F g⁻¹ at 1 A g⁻¹ in a three-electrode system and a two-electrode system, respectively, which was superior to that of most analogous materials reported previously. Additionally, it also demonstrated excellent cyclic stability, retaining 90% of its capacitance after 10 000 cycles in a three-electrode system using a 1 mol L⁻¹ Na₂SO₄ electrolyte. The high supercapacitor performance of CTFTTF@2-700 can be attributed to its high specific surface area, optimal micropore-to-mesopore ratio and significant content of heteroatoms, specifically sulfur and nitrogen.