Advanced Materials

Biography

Biography: Hanaa Dawoud

Abstract

The depletion of fossil fuel and global warming concerns related to burning fossil fuel has increased the demand for progress in high-performance energy conversion and energy storage devices. For this reason, flexible all solid CNTs/MnO₂ hybrid electrode produced hybrid supercapacitors have been assembled for first time via RF magnetron sputtering technique to deposit MnO₂ at carbon nanotube (CNTs) composite layer.The electrode synthesis has been done in two steps, CNTs sheet produced via floating catalyst chemical vapor deposition (CVD), followed by the deposition of MnO₂ on CNTs sheet by RF magnetron sputtering. The significant aspect of sputtered MnO₂ material is that it binds directly to CNTs without any binder’s requirement. In this case, the areal capacitance is increased with great stability over long cycling. CNTs electrode worked as a current collector and CNTs/MnO₂ composite film operated as an active layer. The surface morphology and microstructure of the CNTs and CNTs/MnO₂ electrodes were characterized by scanning electron microscope-energy dispersive spectroscopy (SEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and Raman spectroscopy. It was found that the 1 µm thick MnO₂ film covered the upper surface of CNTs sheet with a mass loading of MnO₂ reaches 0.125 mg/cm². Moreover, the electrochemical measurements of the CNTs/MnO₂ sheet in 1 M of Na₂SO₄ were examined via electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD). The CNTs/MnO₂ electrode showed the highest specific capacitance of CV (1676 F/g at 5 mV/s) and excellent performance of specific capacitance and cyclic stability with capacitance retention of 98.4% after 600 cycles from charge/discharge process. In a two-electrode system with a PVA/H₃PO₄/CNTs/MnO₂ symmetric capacitor, the initial capacitance decreased by only 33% after 500 cycles.