Chemical vapor deposition-grown single-layer graphene-supported nanostructured Co3O4 composite as binder-free electrode for asymmetric supercapacitor and electrochemical detection of caffeic acid

In this study, we developed a monolayer graphene/nanostructured cobalt oxide (MLG/Co ₃O ₄ ) composite for asymmetric supercapacitor and electrochemical sensor applications. The MLG was grown by chemical vapor deposition process and the Co ₃O ₄ nanostructures were electrodeposited on the MLG surface. Scanning electron microscopy proved that there were flower-like nanostructured Co ₃O ₄ densely electrodeposited on the MLG surface. At a current density of 3 mA cm ⁻², the MLG/Co ₃O ₄ composite produced an areal capacitance of 3.73 F cm ⁻². After 10,000 cycles, the composite electrode still had 93.6 % of its initial capacitance at 5 mA cm ⁻². The asymmetric system displayed an areal capacitance of 929 mF cm ⁻² at 4 mA cm ⁻² with good cycle stability. The asymmetric electrode produced a specific energy of 51 μWh cm ⁻² and a specific power of 11.1 mW cm ⁻² . Cyclic voltammetric measurements demonstrated that the composite showed redox peaks at 0.48 eV and 0.09 eV toward the determination of CA. With a sensitivity of 0.13 µA/µM/cm ² and a limit of detection of 0.009 µM, the composite showed CA concentrations, ranging from 0.5 to 480 M. The composite displayed excellent selectivity and the current produced for the interfering compounds was exceedingly low. Using the composite electrode, the spiked CA in red wine and green tea samples recovered remarkably effectively.