Synthesis, characterization and electrochemical properties of activated coconut fiber carbon (ACFC) and CuO/ACFC nanocomposites for applying as electrodes of supercapacitor devices

CuO nanoparticles (CuO NPs) and CuO/Activated Coconut Fiber Carbon nanocomposites (CuO/ACFC Ncps) with different ACFC loading of 0.1, 0.2, 0.3, and 0.4 g (designated as CuO/ACFC-1, 2, 3, 4 Ncps, respectively) were prepared by a one-pot hydrothermal method. CuO NPs and all CuO/ACFC Ncps displayed a monoclinic phase of CuO with space group C2/c as confirmed by X-ray diffraction. Field emission scanning electron microscopy revealed a lotus root-like shape with grooves on a rough surface of ACFC and an oval-like shape for CuO NPs. Transmission electron microscopy revealed a bar-let shape of CuO NPs with average diagonal of 167.57 +/- 2.32 nm. Cyclic voltammetry, galvanostatic charge/discharge and electrochemical impedance spectroscopy were performed to probe the electrochemical properties of all samples. Interestingly, the specific capacitance (Cs) of 60.14 F g (-1) for CuO NPs electrode was improved to 145.33 F g(-1) at 1 A g(-1) in CuO/ACFC-0.3 Ncps electrode with capacity retention of 85.24%. Moreover, an assembled asymmetric supercapacitor (ASC) device with ACFC as a negative electrode and CuO/ACFC-3 Ncps as a positive electrode (ACFC//CuO/ACFC-3) could exhibit the Cs value of 24.94 F g(-1) at 0.5 A g(-1) with the maximum energy density (Esp) and power density (Psp) of 7.78 Wh kg(-1) and 3,000 W kg(-1), respectively. Additionally, good capacitance retention of 75.2% was achieved in this device after 1500 continuous GCD cycling test.

Automated summary

In this study, CuO nanoparticles and CuO/Activated Coconut Fiber Carbon nanocomposites were prepared and their electrochemical properties were tested. The specific capacitance was improved in the CuO/ACFC-0.3 Ncps electrode and an assembled asymmetric supercapacitor device showed good energy density and power density. The capacitance retention after continuous cycling test was also satisfactory at 75.2%.