Supercapacitor electrodes, composed of vertically-oriented graphene (VG) and MnO2, are synthesized on native SiO2-passivated silicon wafers. The VG layers with a thickness of ~3 μm are deposited directly on the substrates via plasma-enhanced chemical vapor deposition (PECVD). The distribution levels of MnO2 formed with the electrodepositing method are investigated by using different types of solutions. The deeper infiltration of MnO2 depositions produced with ethanol/water solution is observed. The capacitance retention of 75.22% from a scan rate of 20 mV/s to 100 mV/s with ethanol/water solution, compared with that of 60.72% using water solution, suggests the better rate capability. The specific capacitance as high as 470.80 mF/cm2 at 20 mV/s is achieved with the increasing loadings of MnO2. The original retention of 99.29% after 5000 cycles demonstrates the excellent cycling stability, which is ascribed to the strong bonds between VG/SiO2/Si and MnO2/VG. The promising supercapacitor electrodes in this study provide a potential for forming high-performance supercapacitor devices based on silicon wafer substrates.
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