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In this study, we present results of a mathematical model in which the governing equations of electroforming process were solved using a robust finite element solver (COMSOL Multiphysics). The effects of different parameters including applied current density, solution electrical conductivity, electrode spacing, and anode height on the copper electroforming process have been investigated. An electroforming experiment using copper electroforming cell was conducted to verify the developed model. The obtained results show that by increasing the applied current density, the electroforming process takes place faster, thereby resulting in a higher thickness of the electroformed layer. In addition, higher applied current density led to non-uniformity of the coated layer. It was revealed that by increasing electrolytic conductivity from 5 to 20 S/m, the electroformed layer became thicker. By considering three different anode heights, it was found that if the cathode and anode are the same height, the process will be more effective. Finally, it was concluded that there is an optimum value of anode-cathode spacing: above it, energy consumption and plating time are high; while below it, the resultant layer is non-uniform. The present study demonstrates that the developed model can accurately capture the physics of electroforming with a reasonable computational time.

In recent years, the intrinsic magnetic properties of magnetic nanoparticles (MNPs) have made them one of the most promising candidates for magnetic resonance imaging (MRI). This study aims to evaluate the effect of different coating agents (with and without targeting agents) on the magnetic property of MNPs. In detail, iron oxide nanoparticles (IONPs) were prepared by the polyol method. The nanoparticles were then divided into two groups, one of which was coated with silica (SiO2) and hyperbranched polyglycerol (HPG) (SPION@SiO2@HPG), the other was covered by HPG alone (SPION@HPG). In the following section, folic acid (FA), as a targeting agent, was attached on the surface of nanoparticles. Physicochemical properties of nanostructures were characterized using Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), and a vibrating sample magnetometer (VSM). TEM results showed that SPION@HPG was monodispersed with the average size of about 20 nm, while SPION@SiO2@HPG had a size of about 25 nm. Moreover, HPG coated nanoparticles had much lower magnetic saturation than the silica coated ones. The MR signal intensity of the nanostructures showed a relation between increasing the nanoparticle concentrations inside the MCF-7 cells and decreasing the signal related to the T2 relaxation time. The comparison of coating showed that SPION@SiO2@HPG (with/without a targeting agent) had significantly higher r2 value in comparison to Fe3O4@HPG. Based on the results of this study, the Fe3O4@SiO2@HPG-FA nanoparticles have shown the best magnetic properties, and can be considered promising contrast agents for magnetic resonance imaging applications.

In this work, we report a facile chemical precipitation method to prepare zinc manganite (ZnMn2O4) materials. ZnMn2O4 nanosheets were synthesized through a cathodic electrolytic electrodeposition (ELD), and their application as supercapacitor electrodes were evaluated. The effect of calcining temperature on the nanostructure and morphology of ZnMn2O4 was investigated systematically through scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), FTIR spectroscopy, X-ray diffractometery (XRD), X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller (BET) surface area measurements. Electrochemical properties of the synthesized products as electrodes in a supercapacitor device were studied using cyclic voltammetry (CV), galvanostatic charge/discharge, and electrochemical impedance spectroscopy in aqueous electrolyte. ZnMn2O4 nanosheets exhibiting remarkable electrochemical performance in supercapacitors with specific capacitance (∼457 F g−1 at 1 A g−1), excellent rate capability (67.2% capacity retention at 10 A g−1), and good cycling stability (only 92.5% loss after 4000 cycles at 3 A g−1). All the results demonstrate that the synthesis route is cost-effective, facile, and can development for prepared electrode materials in electrochemical supercapacitors.

In recent years, development of high-performance supercapacitor electrode materials has stimulated a great deal of scientific research. The electrochemical performance of a supercapacitor strongly depends on its material structures. Herein, we report a simple strategy for high-performance supercapacitors by building pseudocapacitive CuS nanospheres with nanoporous structures, nanosized walls (

In this study, a thermal method was used to synthesize spinel NiCo2O4 and carbon nanotubes (CNTs)@NiCo2O4 with an average size 50 nm and 20 nm, respectively. Addition of CNTs into NiCo2O4 noticeably increases the active surface area compared to pure spinel NiCo2O4. SEM analyses showed that the morphologies are spherical in both pure and composite samples. Uniform CNTs@NiCo2O4 nanoparticles exhibit high specific capacitance of 210 F g−1 at 2 A g−1 and a good retention capacity of 92.70% after 2500 cycles, which shows a considerable improvement compared to NiCo2O4. Additionally, an exceptional rate capability of about 73.2% was obtained at 50 A g−1. Such remarkable electrochemical performance of the CNTs@NiCo2O4 can be attributed to high specific surface area and also uniform structure which increase the exposure of active sites available for reaction on the surface shortened transport pathways for both electrons and ion. Also, volume change during the charge-discharge process is mainly alleviated compared to pure spinel NiCo2O4. A carbonaceous material such as the CNT facilitates the charge transfer and improves the stability of frame against volume change.

Due to unique advantages, the development of high-performance supercapacitors has stimulated a great deal of scientific research over the past decade. The electrochemical performance of a supercapacitor is strongly affected by the surface and structural properties of its electrode materials. Herein, we report a facile synthesis of high-performance supercapacitor electrode material based on CuS nano-hollow spheres with nanoporous structures, large specific surface area (97 m2 g−1) and nanoscale shell thickness (

ZnCo2O4 nanoflakes were directly grown on Ni foam via a two-step facile strategy, involving cathodic electrolytic electrodeposition (ELD) method and followed by a thermal annealing treatment step. The results of physical characterizations exhibit that the mesoporous ZnCo2O4 nanoflakes have large electroactive surface areas (138.8 m2 g−1) and acceptable physical stability with the Ni foam, providing fast electron and ion transport sites. The ZnCo2O4 nanoflakes on Ni foam were directly used as integrated electrodes for supercapacitors and their electrochemical properties were measured in 2 M KOH aqueous solution. The ZnCo2O4 nanoflake electrode exhibits a high capacitance of 1781.7 F g−1 at a current density of 5 A g−1 and good rate capability (62% capacity retention at 50 A g−1). Also, an excellent cycling ability at various current densities from 5 to 50 A g−1 was obtained and 92% of the initial capacitance maintained after 4000 cycles. The results demonstrate that the proposed synthesis route is cost-effective and facile and can be developed for preparation of electrode materials in other electrochemical supercapacitors.

In this work, a novel ternary composite consisting of polyaniline–reduced graphene oxide–cobalt sulfide (PANI–rGO–CoS) was prepared by a two-step process. In the first step, a simple and cost effective hydrothermal route was employed for the synthesis of cubic cobalt sulfide (CoS) on the graphene oxide sheets. In the second step, the polyaniline nanorods were grown on the surface of rGO–CoS sheets via in situ aniline chemical polymerization which was synergistically attached to the graphene surface. The structure and morphology of resulting ternary composite were characterized using Fourier transform infrared spectroscopy, X-ray diffraction, and field-emission scanning electron microscopy. The obtained cubic CoS which was incorporated in ternary composite exhibited significant increase in specific capacitance compared to binary polyaniline–reduced graphene oxide (PANI–rGO) composite. Electrochemical measurements demonstrated that the specific capacitance of the ternary PANI–rGO–CoS composite was 431 F g−1 at the current density of 0.5 A g−1 in 1 M H2SO4 solution, which was significantly higher than that of the binary PANI–rGO composite (276 F g−1). In addition, the composite displayed good cycle stability retaining 90.1% of their original specific capacitance after 1000 charge–discharge cycles.

An in-situ polymerization method has been employed to prepare CuO/PANI nanocomposite. The prepared samples have been characterized by X-ray diffraction (XRD), FTIR spectroscopy, field emission scanning electron microscopy (FESEM), and BET analysis. Application of the prepared samples has been evaluated as supercapacitor material in 1 M Na 2 SO 4 solution using cyclic voltammetry (CV) in different potential scan rates, ranging from 5 to 100 mV s −1 , and electrochemical impedance spectroscopy (EIS). The specific capacitance of CuO/PANI has been calculated to be as high as 185 F g −1 , much higher than that obtained for pure CuO nanoparticles (76 F g −1 ). Moreover, the composite material has shown better rate capability (75% capacitance retention) in various scan rates in comparison with the pure oxide (30% retention). EIS results show that the composite material benefits from much lower charge transfer resistance, compared to CuO nanoparticles. Moreover, much better cyclic performance has been achieved for the composite material.

In this work, we have developed a novel nanocomposite via deposition of ceria (CeO2) on nitrogen-doped reduced graphene (CeO2/NRGO). NRGO was synthesized through a facile, safe, and scalable method to achieve simultaneous thermal reduction along with nitrogen doping of graphene oxide (GO) in air at much lower reaction temperature. CeO2/NRGO was prepared via a sonochemical method in which ceria nanoparticles were uniformly distributed on NRGO sheets. The structure and morphology of CeO2/NRGO nanocomposites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR), and Raman spectroscopy. Electrochemical properties of the proposed nanocomposite electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge/discharge, continuous cyclic voltammetry (CCV), and electrochemical impedance spectroscopy (EIS) measurements. CeO2–NRGO nanocomposite electrodes showed excellent supercapacitive behavior, including much higher specific capacitance (230 F g−1 at 2 mV s−1) and higher rate capability compared to pure N-graphene. The cycling stability of the electrodes was measured by continues cyclic voltammetry (CCV) technique. The CCV showed that the specific capacitance of the CeO2/NRGO and NRGO nanocomposite maintained at 94.1 and 93.2% after 4000 cycles. The results suggest its promising potential as efficient electrode material for supercapacitors.

A facile electrostatic co-precipitation route has been employed to prepare f-SWCNT/Co 3 O 4 nano-composite. The prepared samples have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and BET. Application of the prepared samples has been evaluated as supercapacitor material in 6 M KOH solution using cyclic voltammetry in different potential scan rates, ranging from 5 to 50 mV s−1, and electrochemical impedance spectroscopy (EIS). The specific capacitance of f-SWCNT/Co 3 O 4 has been calculated to be as high as 343 F g−1, much higher than that of obtained for pure Co 3 O 4 nanoparticles (77 F g−1). Moreover, the composite material has shown better rate capability (55 % capacitance retention) in various scan rates in comparison with the pure oxide (40 % retention). The composite material also showed excellent cycling performance (92 % capacitance retention) over 5,000 continuous cycles. EIS results show that the composite material benefits form much lower charge transfer resistance, compared with Co 3 O 4 nanoparticles.

In this study, Copper (Cu) nanostructures (CuNS) were electrochemically deposited on a film of multiwall carbon nanotubes (MWCNTs) modified pencil graphite electrode (MWCNTs/PGE) by cyclic voltammetry method to fabricate a CuNS-MWCNTs composite sensor (CuNS-MWCNT/PGE) for hydrazine detection. Scanning electron microscopy (SEM) and Energy-dispersive X-ray spectroscopy (EDX) were used for the characterization of CuNS on the MWCNTs matrix. The composite of CuNS-MWCNTs was characterized with cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The preliminary studies showed that the proposed sensor have a synergistic electrocatalytic activity for the oxidation of hydrazine in phosphate buffer. The catalytic currents of square wave voltammetry had a linear correlation with the hydrazine concentration in the range of 0.1 to 800μM with a low detection limit of 70nM. Moreover, the amperometric oxidation current exhibited a linear correlation with hydrazine concentration in the concentration range of 50-800μM with the detection limit of 4.3μM. The proposed electrode was used for the determination of hydrazine in real samples and the results were promising. Empirical results also indicated that the sensor had good reproducibility, long-term stability, and the response of the sensor to hydrazine was free from interferences. Moreover, the proposed sensor benefits from simple preparation, low cost, outstanding sensitivity, selectivity, and reproducibility for hydrazine determination.

Palladium nanostructures have been deposited onto the stainless steel electrode by simple electrochemical deposition method in a buffer solution. The morphology of the synthesized Pd nanoparticles is controllable by deposition potentials because the driving force for various crystal growth mechanisms is merely dependent on applied potentials. The deposited Pd nanoparticles at higher applied potentials showed a cauliflower-like morphology with a nanoscale structure and large surface area. Then, an amperometric hydrogen sensor based on Pd nanoparticles can be constructed. This sensor is based on polymer electrolyte membrane fuel cell (PEMFC) and can be used at the ambient temperature. It is operated in the three-electrode mode that consists of three electrodes (working, counter and reference) and protonated Nafion membrane as proton conducting solid polymer electrolyte (SPE). The steady-state current response is obtained linearly to the concentrations of hydrogen from 50 to 2000 ppm, when a fixed potential of 0.2V is applied to the sensor. Typical factors that influence the performance of the sensor are analyzed and discussed. The simple and inexpensive hydrogen sensor fabricated shows low LOD (10 ppm, based on S/N = 3), wide linear range (50-2000 ppm) and short response time (10-40 s).