Imine-Linked π-Conjugated Covalent Organic Frameworks as an Efficient Electrode Material for Pseudocapacitive Energy Storage
Santu Ruidas, Lingaraj Pradhan, Bishnupad Mohanty, Sasanka Dalapati, Saurav Kumar, Bikash Kumar Jena, Asim Bhaumik
Abstract
Covalent organic frameworks (COFs), having a very diverse structural makeup, flexibility, nanoscale porosity, and exceptionally high surface area, have recently attracted a huge amount of interest as the emerging materials for energy and environmental research. Herein, by employing the Schiff base reaction route, we planned and synthesized two imine-linked π-conjugated COFs (IC–COFs), i.e., TFPh-NDA and TFR-NDA, and explored them as electrode materials for asymmetric supercapacitor application. The TFPh-NDA and TFR-NDA IC-COFs possess high crystallinity and a large surface area with bimodal porosity. The imine-linked π-conjugated COFs showed a redox-active behavior and exhibited an outstanding gravimetric capacitance of 583 F·g –1 for TFPh-NDA and 362 F·g –1 for TFR-NDA in a three-electrode configuration. The TFPh-NDA IC-COF//activated carbon (AC)-based asymmetric supercapacitor devices (ASDs) exhibit a wide voltage window of 2.5 V (−1.0 to 1.5), indicating its potentiality in the supercapacitor market. The specific capacitance of the ASD was evaluated at different scan rates, with a maximum specific capacitance of 323.25 F·g –1 at 1 mV·s –1 . Moreover, at a power density of 404.06 W·kg –1, the ASD has a maximum energy density of 280.58 W h·kg –1 . The as-fabricated TFPh-NDA IC-COF//AC ASD exhibits an ultrastable capacitance retention of 98% of its initial capacitance even after 10,000 CV cycles. This discovery is an example of a prospective contender for applications involving capacitive storage.