Biomass-engineered rGO coupled with ytterbium doped cobalt pyrovanadate: A sustainable electrode material for supercapacitor and OER activity

The advancement of next-generation energy storage and conversion technologies depends on the fabrication of high-performance sustainable electrode materials. The current work explores the environmentally benign method for the synthesis of reduced graphene oxide (rGO) from activated carbon generated from waste mango seeds. Ytterbium-doped cobalt pyrovanadate (Yb@Co₂V₂O₇:CoV) nanoparticles were anchored to rGO through the solvothermal method to generate Yb@CoV-rGO nanocomposite. The materials were used as electrode material for supercapacitor applications and observed a specific capacitance (Csp) of 128, 413 and 769 F/g at a scan rate of 2 mV/s using the cyclic voltammetry technique. An asymmetric device was also fabricated using synthesized activated carbon as the negative electrode and Yb@CoV-rGO nanocomposite as the positive electrode, resulting in a specific capacitance (Csp) of 414.5 F/g at a current density of 1 mA/g in 0.1 M H₂SO₄. In addition, oxygen evolution reaction (OER) studies were conducted and observed overpotentials of 320 mV and 510 mV in the presence of Yb@CoV-rGO and Yb@CoV, respectively, at 10 mA/cm² current density. The Tafel slope for Yb@CoV-rGO and Yb@CoV was found to be 196 and 394 mV/dec. Under both the electrochemical studies, Yb@CoV-rGO showed enhanced electrochemical performance compared to the other two pristine materials. The enhanced conductivity, superior redox behavior, effective OH⁻ adsorption and oxygen release could be reasons for enhanced activity in the Yb@CoV-rGO nanocomposite. The obtained results justify Yb@CoV-rGO's dual electrochemical activity for energy storage and conversion. The conversion of waste into energy-generating value-added products aims to address environmental and energy sector issues.