Binder-free vertical graphene nanosheets templated NiO petals for high-performance supercapacitor applications

Abstract

Transition metal oxide and carbon-based hybrid nanostructures with high charge capacity and rate capabilities are emerging as promising electrodes for commercial supercapacitor devices. Herein, we report the fabrication of binder-free supercapacitor electrodes of vertical graphene nanosheets (VGN) templated NiO petals. The NiO petals are grown under different background O2 pressure, deposition temperature, and the number of laser shots using pulsed laser deposition (PLD). The morphology, microstructure, and stoichiometry of the NiO petals are greatly influenced by the background O2 pressure and deposition temperature. The increase in deposition temperature has been found to increase the particle size, whereas the number of laser shots affected the morphology and stoichiometry. Further, the VGN templated growth facilitates the NiO to possess a high surface area and, in turn, results in ∼2.5 times higher areal capacitance than the NiO directly grown on carbon paper substrate without VGN. In the present study, the VGN templated NiO petals exhibited areal capacitance as high as 175 mF/cm2 @ 0.1 V/s. The high areal capacitance is correlated with morphology, microstructure, particle size, and mass loading. An asymmetric coin cell device fabricated using NiO/VGN hybrid and oxygenated VGN electrodes exhibited energy and power densities of 0.4 μWh/cm2 and 102 μW/cm2, respectively. Further, LED lighting using the coin cell reveals the potential utilization of NiO/VGN hybrid electrodes for commercial applications.