Arshid Numan

Facile sonochemical synthesis of nanostructured NiO with different particle sizes and its electrochemical properties for supercapacitor application

In this work, we demonstrate the influence of nickel oxides with divergent particle sizes as the working electrodes for supercapacitor application. The nanostructured nickel oxide (NiO) is synthesized via facile sonochemical method, followed by calcination process. The crystallinity and surface purity of prepared samples are clearly examined by X-ray diffraction and Raman analysis. NiO crystallinity is significantly increased with increasing calcination temperatures. The surface analysis confirmed that the calcination at 250°C exhibited nanoclutser like NiO with average particle size of ∼6nm. While increasing the calcination temperature beyond 250°C, hexagonal shaped NiO is observed with enhanced particle sizes. The electrochemical performance confirmed the good redox behavior of NiO electrodes. Moreover, NiO with average particle size of ∼6nm exhibited high specific capacitance of 449F/g at a scan rate of 5mV/s compared to other samples with particle sizes of ∼21nm (323F/g) and ∼41nm (63F/g). This is due to the good ion transfer mechanism and effective electrochemical utilization of the working electrode.

Enhanced electrochemical performance of cobalt oxide nanocube intercalated reduced graphene oxide for supercapacitor application

We investigated different molar concentrations of cobalt precursor intercalated reduced graphene oxide (rGO) as possible electrode materials for supercapacitors. Cobalt oxide (Co3O4) nanocubes intercalated reduced graphene oxides (rGO) were synthesized via a facile hydrothermal method. It has been found that the Co3O4 particles with a cubical shape are decorated on rGO matrix with an average size of ∼45 nm. The structural crystallinity of rGO–Co3O4 composites was examined by X-ray diffraction (XRD). Raman spectroscopy confirmed the successful reduction of GO to rGO and effective interaction between Co3O4 and the rGO matrix. The electrochemical performances of rGO–Co3O4 electrodes were examined using cyclic voltammetry and charge–discharge techniques. The maximum specific capacitance (278 F g−1) is observed at current density of 200 mA g−1 in the C2 electrode resulting from effective ion transfer and less particle aggregation of Co3O4 on the rGO matrix than in the other electrodes. C2 exhibits good rate capability and excellent long-term cyclic stability of 91.6% for 2000 cycles. The enhanced electrochemical performance may result from uniform intercalation of cobalt oxide over the rGO. These results suggest that the Co3O4 intercalated rGO matrix could play a role in improved energy storage capability.

Ultrahigh capacitance of amorphous nickel phosphate for asymmetric supercapacitor applications

This article presents the effect of different calcination temperatures on the structural, morphological and capacitance of nickel phosphate (Ni3(PO4)2) as an electrode material for supercapacitor applications. Ni3(PO4)2 was synthesized via a sonochemical method followed by calcination at different temperatures (300, 600 and 900 °C, denoted as N300, N600 and N900, respectively). The phase structure and purity of Ni3(PO4)2 were confirmed by X-ray diffraction (XRD) and Fourier transform infrared (FTIR) analysis. The surface morphologies showed that the particle size increased with increasing the calcination temperatures. The electrochemical performance of N300, N600 and N900 were investigated using cyclic voltammetry (CV) and galvanostatic charge–discharge (GCD) in a 1 M KOH electrolyte. It was found that N300 exhibited the maximum specific capacity of 620 C g−1 at 0.4 A g−1, which was significantly higher than N600 (46 C g−1) and N900 (14 C g−1). Here, the enhanced electrochemical performance was obtained due to the amorphous structure and augmentation of the redox active sites of the N300 particles. Additionally, the fabricated N300//activated carbon based asymmetric supercapacitor can be cycled reversibly at a cell voltage of 1.45 V. The device exhibited an energy density of 76 W h kg−1 and a power density of 599 W kg−1 with life cycles of 88.5% capacitance retention after 3000 cycles.

An Approach to Solid-State Electrical Double Layer Capacitors Fabricated with Graphene Oxide-Doped, Ionic Liquid-Based Solid Copolymer Electrolytes

Solid polymer electrolyte (SPE) composed of semi-crystalline poly (vinylidene fluoride-hexafluoropropylene) [P(VdF-HFP)] copolymer, 1-ethyl-3-methylimidazolium bis (trifluoromethyl sulphonyl) imide [EMI-BTI] and graphene oxide (GO) was prepared and its performance evaluated. The effects of GO nano-filler were investigated in terms of enhancement in ionic conductivity along with the electrochemical properties of its electrical double layer capacitors (EDLC). The GO-doped SPE shows improvement in ionic conductivity compared to the P(VdF-HFP)-[EMI-BTI] SPE system due to the existence of the abundant oxygen-containing functional group in GO that assists in the improvement of the ion mobility in the polymer matrix. The complexation of the materials in the SPE is confirmed in X-ray diffraction (XRD) and thermogravimetric analysis (TGA) studies. The electrochemical performance of EDLC fabricated with GO-doped SPE is examined using cyclic voltammetry and charge–discharge techniques. The maximum specific capacitance obtained is 29.6 F∙g−1, which is observed at a scan rate of 3 mV/s in 6 wt % GO-doped, SPE-based EDLC. It also has excellent cyclic retention as it is able keep the performance of the EDLC at 94% even after 3000 cycles. These results suggest GO doped SPE plays a significant role in energy storage application.

Binary nanocomposite based on Co3O4 nanocubes and multiwalled carbon nanotubes as an ultrasensitive platform for amperometric determination of dopamine

AbstractComposites containing cobalt oxide (Co3O4) nanocubes integrated with multiwall carbon nanotubes (MWCNT) were synthesized by a hydrothermal route. The fractions of MWCNTs in the composite were varied from 4, 8, 12, 16 and 20 wt.%, and the resulting materials are denoted as C1, C2, C3, C4 and C5, respectively. The formation of products with high structural crystallinity was confirmed by X-ray photoelectron spectroscopy, Raman spectroscopy and X-ray diffraction. A morphological study by field emission scanning electron microscopy and high resolution transmission electron microscopy showed the successful integration of Co3O4 nanocubes to the MWCNTs with an average particle size of ∼32 nm. The surface of a glassy carbon electrode (GCE) was modified with the nanocomposites in order to evaluate the electrochemical performance of the nanocomposites. Cyclic voltammetry showed that the C4-modified GCE displays best performance in terms of oxidation potential and peak current in comparison to that of a bare GCE, Co3O4 nanocubes, or GCEs modified with C1, C2, C3 or C5. The detection limit (at an S/N ratio of 3) is 0.176 nM by using chronoamperometry, and the linear range is between 1 and 20 μM. Graphical abstractMWCNT-Co3O4 nanocubes were synthesized by one pot hydrothermal route. The nanocomposite is used for electrochemical detection of dopamine. The limit of detection is found to be 176 nM by chronoamperometry at a constant potential of + 0.13 V.

Poly(Acrylic acid)–Based Hybrid Inorganic–Organic Electrolytes Membrane for Electrical Double Layer Capacitors Application

Nanocomposite polymer electrolyte membranes (NCPEMs) based on poly(acrylic acid)(PAA) and titania (TiO2) are prepared by a solution casting technique. The ionic conductivity of NCPEMs increases with the weight ratio of TiO2.The highest ionic conductivity of (8.36 ± 0.01) × 10−4 S·cm−1 is obtained with addition of 6 wt % of TiO2 at ambient temperature. The complexation between PAA, LiTFSI and TiO2 is discussed in Attenuated total reflectance-Fourier Transform Infrared (ATR-FTIR) studies. Electrical double layer capacitors (EDLCs) are fabricated using the filler-free polymer electrolyte or the most conducting NCPEM and carbon-based electrodes. The electrochemical performances of fabricated EDLCs are studied through cyclic voltammetry (CV) and galvanostatic charge-discharge studies. EDLC comprising NCPEM shows the specific capacitance of 28.56 F·g−1 (or equivalent to 29.54 mF·cm−2) with excellent electrochemical stability.

Passively Q-switched erbium-doped fibre laser using cobalt oxide nanocubes as a saturable absorber

Abstract We demonstrate a Q-switched Erbium-doped fibre laser (EDFL) utilizing cobalt oxide (Co3O4) nanocubes film based saturable absorber (SA) as a passive Q-switcher. Co3O4 nanocubes are embedded into a polyethylene oxide film to produce a high nonlinear optical response, which is useful for SA application. It has saturation intensity and modulation depth of 3 MW/cm2 and 0.35%, respectively. The proposed laser cavity successfully generates a stable pulse train where the pulse repetition rate is tunable from 29.8 to 70.92 kHz and the pulse-width reduces from 10.9 to 5.02 μs as the 980 nm pump power increases. This result indicates that the Co3O4 is excellent for constructing an SA that can be used in producing a passively Q-switched fibre laser operating at a low pump intensity. To the best of our knowledge, this is the first demonstration of Co3O4 film based fibre laser.