A mesoporous nickel oxide nanosheet as an electrode material for supercapacitor application using the 1-($$2^\prime $$,$$3^\prime $$-dihydroxypropyl)-3-methylimidazolium hydroxide ionic liquid electrolyte

NiO nanosheets were deposited on the surface of a stainless steel substrate by using a facile, environmentally friendly, reflux deposition approach for supercapacitor (SC) applications. X-ray diffraction patterns and field emission scanning electron microscopy images revealed the formation of a face centred cubic crystal structure with a uniform, compact, smoothly ordered nanosheet like structure. This study focuses on the electrochemical supercapacitive properties of NiO nanosheets with respect to cyclic voltammetry, galvanostatic charge–discharge and electrochemical impedance spectroscopy techniques in a 1-((2^prime {,}3^prime )-dihydroxypropyl)-3-methylimidazolium hydroxide [DHPMIM][OH] ionic liquid (IL) as an electrolyte. The electrochemical study revealed that NiO (0.3 M) showed a high-specific capacitance of (hbox {205.5 F g}^-1) and an excellent cycling stability (80% specific capacitance retention after 5000 cycles) in the [DHPMIM][OH] IL electrolyte. Thus, the result showed that NiO nanosheets act as an active electrode material hold for SCs.