Electropolymerized chlorophyll derivative biopolymers for supercapacitors

Abstract

Chlorophylls (Chls) have rarely been prepared and studied in the polymeric phase. We demonstrate for the first time the preparation of four polymerized thin films of chlorophyll derivatives, via the electrochemical coupling of peripheral vinyl or ethynyl groups at the C3-position of the tetrapyrrole ring. The characterization of these PolyChl (polymerized chlorophylls) films suggests that Zn-based PolyChls remain in the chlorin macrocycle, whereas Ni-based PolyChls turn into porphyrin macrocycles during the electropolymerization processes. Employing these PolyChls as the working electrodes in a three-electrode system, the highest capacitance 466 F g−1 at 5 mV s−1 is obtained for PolyNiChl-A. To fully verify the practical value and environment-friendly property, we also fabricate a novel bio-inspired solar light-to-electricity conversion-storage device using a PolyNiChl-A solid-state symmetric supercapacitor and a previously developed all-Chl-based biosolar cell. The device shows excellent photo-charging-discharging behavior under different light illumination intensities. Using non-toxic, degradable, sustainable and pollution-free Chls as dominating material, transferring solar energy to electricity and storing it in supercapacitor, the hybrid energy conversion and storage device suggests a promising way on construction of future clean energy system. Meanwhile this study also creates a novel family of biopolymers with the most abundant, environmentally friendly, and multi-functional Chl derivatives.