Facile preparation of porous single crystal NiO nanoflake array directly grown on nickel foam for supercapacitive electrode material

In this paper, four NiO nano-arrays with different morphology on nickel foam were synthesized by a hydrothermal approach. It is found that the porous single crystal NiO nanoflake array (PNFA) holds superior electrochemical properties , better than the other three samples. The specific capacitance of the PNFA obtained from the cyclic voltammetry curve was 716 F g −1 and that derived from the galvanostatic charge-discharge curve was 589 F g −1 in three-electrode system. The cycling stability of the PNFA could retain as high as 92.4% after 5000 cycles. When the PNFA was assembled into a symmetric supercapacitor , the PNFA//PNFA device exhibited an energy density of 39.3 W h kg −1 (at 550 W kg −1 ) and could retain 13.2 W h kg −1 (at 11,000 W kg −1 ) in two-electrode system. Furthermore, the SEM, XRD, TEM and XPS results prove that the PNFA is a special porous single crystal structure, which combines the advantages of the cross-linked single crystal structure for facilitating electron transfer and the porous structure providing more interfaces for insertion/exit of electrolyte ions from the active material. It indicates that the PNFA is a potential electrode material for supercapacitors .