Nano ZnO@reduced graphene oxide composite for high performance supercapacitor: Green synthesis in supercritical fluid

In this report, zinc oxide nanoparticles (ZnO NPs) decorated reduced graphene oxide (RGO) composite was fabricated by a one-pot approach using supercritical carbon dioxide (scCO2). ScCO2 has gas-like diffusivity, extremely low viscosity, and excellent penetration ability, allowing it to debundle RGO nanosheets and disperse ZnO NPs in between. Owing to the near-zero surface tension and excellent wetting ability of scCO2, the NPs are tightly coated on the highly conductive RGO sheets. The electrochemical characteristics of the ZnO/RGO composite were investigated through cyclic voltammetry, galvanostatic charge-discharge and electrochemical impedance spectroscopy. The composite was capable of delivering a high specific capacitance of 314 F g−1 with excellent cycling stability.