A novel oxidation–reduction route for successive ionic layer deposition of NiO1+x·nH2O nanolayers and their capacitive performance

• Presented a novel method of solution synthesis of NiO1+x·nH2O.
• Synthesized product is formed by nanosheets with thickness of 6–12 nm.
• Electrodes for supercapacitors based on synthesized layers shows high capacity.

Successive ionic layer deposition (SILD) of NiO1+x·nH2O nanolayers was first performed by an oxidation–reduction route using a Ni(NO3)2 and K2S2O8 aqueous solutions. The obtained nanolayers were characterized by SEM, EDX, XRD, XPS, UV–vis and FTIR spectroscopy and electrochemical techniques. The results showed that the as-synthesized product is formed by nanosheets with a thickness of 6–12 nm, having cubic crystal structure of NiO and rhombohedral structure of γ-NiOOH. Electrochemical characterization of the sample prepared by 100 cycles of SILD indicated a capacitive behavior with the specific capacitance value of 1015 F/g at a current density of 1 A g−1 in 1 mol L−1 KOH aqueous solution. Repeated cycling for 3000 charge–discharge cycles demonstrate 10% capacitance fade relative to the initial values. The presented convenient route of synthesis may be used for the preparation of NiO1+x·nH2O nanolayers with high surface area and a large capacitance.

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