Synergistic chlorophyll-derived polymer/NiOx hybrid electrodes for enhanced-performance biobased supercapacitors

Abstract

Chlorophyll (Chl) and its derivatives have emerged as promising pseudocapacitive electrode materials. Nevertheless, substantial challenges remain in further improving their electrochemical performance. To address these challenges, a composite electrode was developed based on a natural Chl-derived polymer, denoted as Poly(NiChl-deoxo), in combination with nickel oxide (NiOx). A porous NiOx interlayer was introduced as an interfacial modifier to synergistically improve electrochemical properties. Porous NiOx films were first fabricated on ITO substrates via spin-coating, followed by electrochemical polymerization of NiChl-deoxo onto these modified surfaces. Characterization results revealed that the significantly increased specific surface area of the Poly(NiChl-deoxo) layer, along with interfacial interactions between NiOx and Poly(NiChl-deoxo), synergistically contributed to the enhanced specific capacitance of the composite electrode. The optimized composite electrode exhibited a specific capacitance of 790 F g−1 at 5 mV s−1 and 626 F g−1 at 1 A g−1. A symmetric supercapacitor based on this composite delivers a specific capacitance of 110 F g−1 at 1 A g−1 and an energy density of 3.8 Wh kg−1. This study demonstrates that the interfacial engineering strategy effectively overcomes the performance limitations of Chl-based electrode materials, offering a novel pathway toward sustainable and environmentally friendly supercapacitors.