Niobium doped triazine based covalent organic frameworks for supercapacitor applications

Abstract

Covalent organic frameworks (COFs) are gaining high importance in energy storage systems due to their uniform porosity and versatile functionality. The present work deals with the fabrication of triazine-based COF through Schiff base formation. The method involves the polycondensation reaction between melamine and terephthalaldehyde. In addition, the COF was also decorated with Niobium to generate Nb@COF. The morphological, elemental mapping, X-ray photoelectron spectroscopy, C13 NMR results show the effective doping of Nb to the COF and provide insights into the nature of bond formation. The obtained experimental XRD results are in good agreement with Materials Studio simulated results. COF and Nb@COF have been used for supercapacitor applications in a three-electrode system. Enhanced specific capacitance was observed in Nb@COF (367 F g−1) compared to pure COF (244 F g−1) at a scan rate of 2 mV s−1. The superior electrochemical performance in Nb@COF could be due to the increased porosity and interlayer spacing. COF and Nb@COF exhibited good stability towards charge and discharge and managed to retain 82 and 89 % specific capacitance, respectively even at 5000 cycles. COF and Nb@COF were assembled in a coin cell and fabricated an asymmetric supercapacitor device as negative and positive electrodes, respectively. The results obtained were satisfactory and shows a specific capacitance of 87 F g−1 at a scan rate of 2 mV s−1.The good stability, specific capacitance and reliability of Nb@COF indicate its potential application in energy storage devices.