Advanced Supercapacitor Applications of a Biopolymer Film Prepared by Electrochemical Polymerization of a Chlorophyll-Derived Nickel Porphyrin

Abstract

Chlorophylls (Chls) are essential pigments in photosynthesis, possessing excellent light absorption properties and superior photoinduced electron transfer abilities. Despite their widespread abundance and rich natural reserves, their practical applications in energy storage devices remain limited due to the inherently poor energy storage capability. In this study, a semisynthetic nickel porphyrin derivative, NiPor-Deoxo, was synthesized from natural Chl-a as a starting material and systematically compared with its chlorin counterpart NiChl-Deoxo. Electrochemical polymerization of both monomeric molecules was successfully achieved via cyclic voltammetry, and it was revealed that most chlorin rings of NiChl-Deoxo underwent further oxidative dehydrogenation under the electropolymerization reaction conditions, ultimately forming a copolymer film similar to the structure of Poly(NiPor-Deoxo). Electrochemical tests revealed that Poly(NiPor-Deoxo) film, prepared from NiPor-Deoxo monomer solution, achieved a specific capacitance as high as 746 F g–1 at a current density of 1 A g–1. To address issues such as electrolyte leakage and complex encapsulation in conventional liquid supercapacitors (SCs), a solid-state gel electrolyte, poly(methyl methacrylate)/polycarbonate/tetrabutylammonium hexafluorophosphate/1,4-dichlorobutane, was explored, and it was used to construct a sandwich-type symmetric solid-state SC based on Poly(NiPor-Deoxo) films. The fabricated SC device retains 80% of its initial capacitance after 20,000 cycles, demonstrating excellent cycling stability as well as outstanding electrochemical reversibility. This study demonstrates that rational synthetic derivatization of natural Chl pigments can significantly enhance their performance and application potential in energy storage systems, providing innovative ideas and pathways for the development of environmentally friendly and sustainable carbon-neutral energy technologies.