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In this paper, porous NiO nanoflake arrays@V 2 O 5 nanoparticles (PNFAs@VNPs) composite is fabricated on Ni foam through a facile hydrothermal process. The PNFAs@VNPs composite has an ordered array structure, a large active surface, and favorable physical stability. Based on the CV profile, the specific capacitance can achieve 950 F g−1 and remain stable at 95.8 % of the original value after 5000 loops. When the PNFAs@VNPs composite is assembled into a symmetric supercapacitor, the energy density can reach 67.0 W h kg−1 at a power density of 550 W kg−1. Even if the power density rises to 11,000 W kg−1, the energy density can still be held at 25.3 W h kg−1. The high supercapacitive property of the PNFAs@VNPs composite is owed to the synergic action of the PNFAs and VNPs. The PNFAs@VNPs composite with the advantages of battery-type and capacitive-type pseudocapacitances has higher charge transfer dynamics, making it a potential supercapacitive electrode material. [Display omitted] • Porous NiO nanoflake arrays (PNFAs) is successfully prepared on nickel foam. • V 2 O 5 nanoparticles (VNPs) are loaded on the PNFAs to form a hierarchical structure. • The PNFAs@VNPs has the advantages of Faraday and intercalation type pseudocapacitor. • The PNFAs@VNPs shows a specific capacitance of 950 F g−1at 5 mV s−1. • The PNFAs@VNPs supercapacitor has an energy density of 67.0 W h kg−1 at 550 W kg−1. [ABSTRACT FROM AUTHOR]

V 2 O 5 nanobelt arrays (VNBAs) is fabricated on Ni foam by using an easy hydrothermal route and then NiO nanosheet arrays (NNSAs) is grown on VNBAs by using a simple chemical bath deposition approach to form VNBAs/NNSAs composite. It is found that the monocrystalline VNBAs with a lamellar structure is uniformly distributed on nickel foam and the polystalline NNSAs with a close packed structure is closely covered on the VNBAs. CV, GCD, EIS and CA electrochemical techniques are used to test the supercapacitive properties of the VNBAs/NNSAs composite. The single electrode displays a high specific capacity of 875 F g−1, a good cycling stability of 96.1%, a small charge transfer resistance of 1.32 Ω and a rapid ion diffusivity of 2.5 × 10−8 cm2 s−1. The symmetric supercapacitor combined by the VNBAs/NNSAs displays a large energy density of 120.1 W h kg−1 at 400 W kg−1 and it retains 68.3 W h kg−1 at 8000 W kg−1. The VNBAs/NNSAs composite with high electrochemical performance is a potential supercapacitor electrode material. [Display omitted] • The V 2 O 5 nanobelt arrays (VNBAs) is successfully prepared on a nickel foam. • The NiO nanosheet arrays (NNSAs) is compounded on the VNBAs to form a hierarchy. • The VNBAs/NNSAs shows a high specific capacitance of 875 F g−1 at 5 mV s−1. • The VNBAs/NNSAs has an energy density of 120.1 W h kg−1 at 400 W kg−1. • The high performance of the VNBAs/NNSAs are ascribed to its synergistic effect. [ABSTRACT FROM AUTHOR]

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. [Display omitted] • Porous single crystal NiO nanoflake array (PNFA) is directly grown on nickel foam. • The PNFA is prepared by a facile hydrothermal method following an annealing process. • The PNFA combines the advantages of porous material and single crystal material. • The PNFA shows a specific capacitance of 716 F g−1 at a scan rate of 5 mV/s. • The PNFA//PNFA supercapacitor has an energy density of 39.3 W h kg−1 at 550 W kg−1. [ABSTRACT FROM AUTHOR]