Triazine-Functionalized Nitrogen-Rich Covalent Organic Framework as an Electrode Material for Aqueous Symmetric Supercapacitor

Abstract

Covalent triazine frameworks, with their ordered pores and crystalline structure that exhibit heteroatom impacts, demonstrate outstanding chemical stability, making them designable for charge storage applications. In this study, the triazine-based covalent organic frameworks (TPT@BDA-COF) was synthesized using 4′,4′′′,4′′′′′-(1,3,5-Triazine-2,4,6-triyl) tris (([1,1′-biphenyl]-4-amine)) (TPT) and 4,4′-Oxydibenzaldehyde (BDA) following polycondensation process. Interestingly, these resulted in the fabrication of a well-connected, orderly porous crystalline structure, redox-active moiety, and significantly high doping atomic percentages of N (~13.6 %). The three-electrode electrochemical study, showed a stable electrochemical potential window of 1.8 V (−0.45 to +1.35) in 1 M NaClO₄ electrolyte, it exhibited a high specific capacitance of 92.6 mF/cm² with a high energy density 41.7 Wh/kg respectively. The symmetric supercapacitor designed using TPT@BDA-COF as both anode and cathode exhibited high specific capacitance (F/g) and gravimetric energy density (Wh/kg): 17.8, 36.9, 43.7, 47.7 and 3.5, 16.6, 13.7, 21.6 in 1 M CH₃COONa, 1 M Na₂SO₄, 1 M NaNO₃, 1 M NaClO₄ electrolyte respectively. It showed excellent cyclic stability (105.2 %), and Coulombic efficiency (97.5 %) even after 10 k GCD cycles in 1 M NaClO₄ at 2 A/g. Interestingly, ClO₄⁻ anions exhibited a better chaotropic nature (water structure breaker) as compared to CH3COO⁻, SO₄⁻², and NO₃⁻. Their energy storage competence is supported by the illumination of 1 white and 1 red LED upon charging a single SSC for 50 sec each. A Quantum Mechanics (QM) calculation and Molecular Dynamics (MD) simulation are performed to investigate and validate the stability of Covalent Organic Frameworks (COFs). DFT calculations were carried out using the SCF approach B3LYP-631G(d) basis set to compute the HOMO and LUMO energies and their respective location in COF.