Functionalization of 0-D and 2-D carbon nitride nanostructures on bio-derived carbon spheres for sustainable electrochemical supercapacitors

•Carbon spheres derived from the Orange Juice through Hydrothermal process.•Functionalization of Carbon spheres with Carbon Nitride structures by one-pot process.•Fabrication of Eco-Friendly Supercapacitor Devices for Sustainability.•ASCs boasts a 1800% increase in PD with a mere 50% decrease in ED. A new carbon nitride nanoparticles-carbon microsphere composite is developed through a green and facile one-step hydrothermal synthesis process with orange juice (Citrus Sinensis) as the carbon source. The orange juice acts simultaneously as a reducing agent for converting melamine into carbon nitride nanostructures to in-situ modify the carbon microsphere surfaces for carbon nitride/carbon sphere heterostructure. The composite material synthesized then is used as an electrochemical electrode in asymmetric supercapacitor devices for charge storage applications. The electrochemical properties of the composite exhibits superior specific capacitance of 350 Fg−1 at 0.5 Ag−1 current density with ∼ 80% capacitance retention at 5 Ag−1 over 2000 charge–discharge cycles. The asymmetric device boasts a 1800% increase in the power density with a mere 50% decrease in the energy density, indicating an exceptional energy-power performance. The superior electrochemical properties of the device are attributed to high active surface sites of the composite with excellent accessibility, conductivity, and chemical interface for favorable charge transport. This novel work should open up the development of green and low-cost charge storage devices from natural biomass for sustainable future.