Green synthesis of NiO nanostructured materials using Hydrangea paniculata flower extracts and their efficient application as supercapacitor electrodes

In this report, for the first time, we have applied green synthesis Ni0 nanoparticles (NiO-NPs) as an electrode material for supercapacitor (SC). Hydrangea paniculata flower extracts were used for the green synthesis of NiO-NPs. The green synthesized NiO-NPs is found to be 33 nm with surface area of 78.472 m(2) g(-1) along with pore volume and pore size of 0.149 cm(3) g(-1) and 4.061 nm. The green synthesized NiO-NPs based electrode exhibit high specific capacitance of 752, 709, 644, 603 and 581 F g(-1) at current densities of 2.5, 5, 10, 20, and 40 Ag-1, respectively, are revealing excellent capacitance retention even at a high current density. More notably, the NiO-NPs electrodes also show outstanding cycling stability up to 5000 cycles at 10 A g(-1) without discernable capacitance fading. This superior electrochemical performance of NiO-NPs is mainly attributed to the nano-dimention of the particles, which shorten the diffusion path lengths for both ions and electrons, ease migration during the rapid charge-discharge process and consequently improve the effective electrochemical utilization of electroactive material. (C) 2017 Elsevier B.V. All rights reserved.