Green biosynthesis of ruthenium oxide nanoparticles on nickel foam as electrode material for supercapacitor applications

Abstract

Ruthenium(IV) oxide (RuO₂) nanoparticles were synthesized via Aspalathus linearis natural extract as a reducing/oxidizing agent, as well as a capping compound. RuO₂ nanoparticles synthesised via a complete green chemistry process would be beneficial for the development of clean, nontoxic and environmentally friendly bio-synthesis procedures. The deposition of RuO₂ nanoparticles on nickel foam (NiF) was carried out to form NiF/RuO₂ electrode material. Structural characterization showed the amorphous nature of the biosynthesized RuO₂, and demonstrated the characteristic peaks of Ni, while the XPS images exhibited the characteristic shape of the Ru 3d, 3p core level peaks, as well as O 1s of the deposited RuO₂ on NiF. The electrochemical investigations of the NiF/RuO₂ electrode showed a high specific capacitance of 750 F g⁻¹ at a current density of 10 Ag⁻¹ for our device measured by using a three-electrode configuration. The NiF/RuO₂ electrode also demonstrated a high rate capability of ∼97.5% capacitance retention at a current density of 10 Ag⁻¹. These results confirmed that the green biosynthesis of RuO₂ on NiF could be a promising method to fabricate supercapacitor electrodes with high electrochemical performance for supercapacitor applications.