Electrodeposition of Binder-Free Peptide/Co(OH)₂ Nanohybrid Electrodes for Solid-State Symmetric Supercapacitors

Organic–inorganic nanohybrids with diverse nanoarchitectures and intrinsic electronic properties are considered as efficient active materials for electrochemical charge storage applications. Herein, we have successfully electrodeposited peptide-based nanohybrids on carbon fiber paper (CP) substrates as the electrodes for the fabrication of symmetric supercapacitors (SCs). The electrodeposition technique has been used for in situ fabrication of a benzo­[2,1,3]­selenadiazole-5-carbonyl-protected BSeYY (BSe = benzo­[2,1,3]­selenadiazole; Y = tyrosine) dipeptide cross-linked with cobalt hydroxide (BSeYY/Co­(OH)₂) on CP without any additives such as binder and conductive materials. The synthesized nanohybrid BSeYY/Co­(OH)₂ has been well characterized. The electrochemical characterization of the nanohybrid electrode has been performed in alkaline electrolytes (1 M KOH and 1 M LiOH). The BSeYY/Co­(OH)₂ nanohybrid shows paramount electrochemical performance in 1 M KOH compared to 1 M LiOH. The electrochemical measurements exhibit an outstanding capacitance of 974.78 F g^–1 at 1 A g^–1 current density and a capacitance retention of 78.62% after 3000 cycles at 18 A g^–1 in 1 M KOH electrolyte. The assembled symmetric SC device exhibits a maximum energy density of 16.35 W h kg^–1 at 0.5 A g^–1 and the highest power density of 617.37 W kg^–1 at 2 A g^–1. The symmetric device represents excellent capacitance retention of 81.04% at 2 A g^–1 after 5000 cycles. The symmetric energy-storage device has been utilized to light up a red light-emitting diode. The efficient charge storage performance of the nanohybrid could be attributed to the cross-linked nanosheet structure with charge-storage sites and fast charge-transport channels.