Bioinspired flavin analogues as organic electrode materials for supercapacitor applications†

With the increasing interest in incorporating redox-active organic molecules as potential materials in energy storage systems, we envisaged a chemical design of a naturally occurring redox-active flavin moiety. Herein, we report the fabrication and characterization of asymmetric supercapacitors (ASCs) based on modified flavins as cathode materials. Notably, subtle chemical modification with the incorporation of a carboxylic functionality around the flavin core (cFl) was found to impart superior ion-storage properties compared to a simple flavin derivative (Fl). As determined, the specific capacitance (SC) for cFl and Fl as individual electrodes was found to be 170 and 62 F g⁻¹, respectively, whereas in a two electrode ASC with activated carbon serving as the anode, the SC was found to be 107 and 29 F g⁻¹, respectively, at a current density of 1.25 A g⁻¹. With better cycling stability (retaining 87% of its initial SC in the case of cFl) and significantly higher energy density (38 W h kg⁻¹ for cFl) as compared to most of the known organic material-based electrodes, the modified flavin derivatives serve as better organic electrode alternatives for practical energy storage applications.