Nanoscale morphology dependent pseudocapacitance of NiO: Influence of intercalating anions during synthesis

Abstract

Three nano-porous NiO samples with high specific surface area were prepared by a simple hydrothermal method under homogeneous precipitation conditions using CTAB as a template and urea as the hydrolysis controlling agent. This study was done to determine the effect of different anions (acetate, nitrate and chloride) present in the precursor salts on the morphology and pseudocapacitance behavior of NiO. The samples were characterized by thermogravimetry (TG), differential scanning calorimetry (DSC), powder X-ray diffraction (PXRD), Brunauer-Emmet-Teller (BET) isotherm and field emission scanning electron microscopy (FESEM). The final NiO samples showed different hierarchical surface morphologies and their effect on the electrochemical pseudocapacitance behavior was carefully studied by cyclic voltammetry, galvanostatic charge-discharge cycles (chronopotentiometry) and impedance spectroscopic techniques. The specific capacitance of NiO sample synthesized by NO3- ion intercalation showed higher surface area, intermediate porosity and a novel pine-cone morphology with nano-wire surface attachments. This sample exhibits the highest pseudocapacitance of 279 F g(-1) at a scan rate of 5 mV s(-1), calculated from the cyclic voltammetry measurements. The sample synthesized by Cl- intercalation shows a nano-flower morphology with lower surface area, porosity and pseudocapacitance behaviour. The NiO sample prepared in the presence of CH3COO- ions showed a honeycomb type surface morphology with an intermediate pseudocapacitance value but higher reversibility. The galvanostatic charge-discharge and impedance spectroscopic measurements on these NiO electrodes were consistent with CV results. The Coulombic efficiency of all the three NiO samples was found to be high (∼85 to ∼99%) after 100 galvanostatic charge-discharge cycles. This study shows that the surface morphology and porosity of NiO are strongly influenced by the anions in the precursor salts, and in turn affect significantly the pseudocapacitance behavior and the power performance of NiO powders.

2 D amorphous frameworks of NiMoO4 for supercapacitors: defining the role of surface and bulk controlled diffusion processes

“…In the present study the specific capacitance values were found to be ~10 % higher as compared to their work [15]. The higher values of specific capacitance can be attributed to the fact that the amorphous nature of the electrodes facilitates more bulk interaction which in turn increases the material utilization [34]. This involvement of the bulk was confirmed from the Wang et al model as shown in Fig.…”

Urchin and sheaf-like NiCo 2 O 4 nanostructures: Synthesis and electrochemical energy storage application

“…The formation of urchin and sheaf-like hierarchical morphologies seems to depend strongly on the temperature of the reaction mixture under hydrothermal conditions. The formation of such surface hierarchical morphologies at different reaction temperatures is governed by a number of factors which include van der Waals forces, hydrogen bonding, hydrophobic attraction, crystal field attraction, electrostatic and dipolar fields, intrinsic crystal contraction and Ostwald ripening [58,59]. The other parameters that would influence significantly the shapes, orientations, growth of crystallites and the final morphology of materials are the energetics and kinetic aspects [60].…”

“…Therefore NiCoO-120-cal sample is relatively better in charge storage performance and higher capacitance than NiCoO-200-cal sample. The specific capacitance was calculated from the discharge curves at different current densities using following equation [13,59]:…”

“…S4). The specific capacitance (F g À1 ) of each sample has been calculated from the CV curves at each scan rate, n (V s À1 ) according to the following equation [59]:…”

Facile synthesis of Cu2O microstructures and their morphology dependent electrochemical supercapacitor properties

“…Although the effect of morphology on supercapacitor property of the anode has been investigated using other materials, a clear relationship between the morphology and property has not been established. 31,38 It is well known that the morphologies of Cu 2 O play a vital role in their physical and chemical properties. 39,40 Therefore, in this study, different morphologies of Cu 2 O were synthesized via a hydrothermal method to examine the effects of morphology on the supercapacitor properties.…”