Highly Pseudocapacitive NiO Nanoflakes through Surfactant-Free Facile Microwave-Assisted Route

A facile and rapid surfactant-free microwave-assisted route is developed to synthesize 10 nm sized NiO nanoflakes with high pseudocapacitive performance for supercapacitor cells. The NiO nanoflakes exhibit mesoporous channels and a surface area as high as 206 m2 g–1 as revealed under BET study, while the structural identity verified by XRD and IR confirm the phase purity of NiO. NiO nanoflakes maintain ∼85% of their thermal stability at temperature 900 °C which can be related to strong intermolecular forces between the NiO nanoparticles held in the molecular matrix. Electrochemical performance investigated in 6 M KOH solution suggests maximum specific capacitance of 307 F g–1 for the NiO∥NiO cell at 0.5 A g–1 sustaining about 96% capacitance after being successfully cycled up to 3000 cycles. The NiO nanoflakes reveal high conductivity of 33.87 S cm–1 at room temperature. Precisely, nanosized NiO bearing “flake” morphology is of particular interest due to the high surface to volume aspect and porosity features—the determining factors for swift ion diffusion into an electrode and improved redox reaction. The illustrated microwave-assisted route unfolds as a direct synthesis method to obtain nanosized NiO flakes with high surface area facilitating excellent device performance characteristics without involving any surface-capping agents.