Multifunctional benzoselenadiazole-capped organic molecule-based nanohybrid for efficient asymmetric supercapacitor and oxygen evolution reaction

Abstract

Nanostructured hybrid materials have attracted significant interest in the field of energy storage and conversion. To investigate the effect of all nanohybrids on electrochemical properties, we have synthesized organic-inorganic nanohybrids through in situ galvanostatic electrodeposition using a monometallic and bimetallic composition of nickel, cobalt salts and an organic molecule. The electrochemical studies reveal that BSeFY/NCDH (20:20) (BSe = benzo[2,1,3]selenadiazole, F = L-phenylalanine and Y = L-tyrosine; NCDH = nickel‑cobalt double hydroxide) hybrid electrode performs more efficiently than 40:0, 0:40, 10:30, 30:10 and nickel‑cobalt double hydroxide-20:20 (NCDH-20:20) electrodes. The specific capacitance of the 20:20 hybrid electrode is measured to be 1338.46 F/g at 2 A/g current density. The AC/NF negative electrode was made using activated carbon, carbon black and polyvinylidene fluoride (PVDF) in a ratio of 80:15:5. The fabricated asymmetric device reveals the energy density of 35.48 Wh/kg at a power density 751.36 W/kg. Furthermore, the device exhibits a capacitance retention of 91.24 % after 5000 cycles at 7 A/g current density. This fabricated device has the ability to illuminate a red LED and operate a small fan. Furthermore, the designed and fabricated hybrid materials are highly efficient for the oxygen evolution reaction (OER). Among the fabricated materials, the 20:20 hybrid electrode is highly active and achieves a lower overpotential of 240 mV with a low Tafel slope of 62 mV/dec at a current density of 10 mA/cm². Furthermore, the BSeFY/NCDH (20,20) hybrid is highly robust and shows negligible activity loss after 55 h of chronopotentiometry measurement at 10 mA/cm² current density. Furthermore, multistep chronopotentiometry was performed in the current density range of 4 to 40 mA/cm² and the results exhibit that the potential rapidly levels off in the next 400 s due to the robust electrochemical stability, rapid mass and electron transportation ability of 20:20 nanohybrid. Therefore, the electrochemical investigations demonstrate that the bimetallic organic-inorganic nanohybrid is highly active in supercapacitor and OER due to its abundant electrochemical active sites, high conductivity, enhanced Faradaic redox properties, multiple valence transitions and the easy synergistic effect between metal ions and organic moiety.