Recently, hollow carbon nanospheres (HCNSs) have played an important role in cutting-edge innovations for energy conversion and storage technologies. To obtain high-performance capacitors, several ...characteristics must be achieved, including high surface area and high diffusion rate of the electrolyte inside the active material. We report herein the electrochemical performance of interconnected HCNSs as a high-capacitive-performance electrode material. After physical characterization, the electrochemical performance of the HCNSs was evaluated experimentally by cyclic voltammetry, galvanostatic charge–discharge (GCD) measurements, and electrochemical impedance spectroscopy. A straightforward facile technique was applied to improve the working electrodes fabricated from HCNSs as electrode material. The HCNSs exhibited excellent cycling stability during 1000 GCD cycles and reasonable capacitive behavior with specific capacitance of 306.38 F g
−1
at a current density of 1 A g
−1
. Also, the stability of the electrode in 3000 cycles of cyclic voltammetry testing was 81%.
Co
3
O
4
nanorods and hybrid reduced graphene oxide (Co
3
O
4
/rGO) were synthesized on a Ni foam substrate using affordable and simple hydrothermal synthesis. Then, the structural and morphological ...investigations of nanoparticles were carried out using X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectroscopy (EDS) mapping, Raman spectroscopy, and Brunauer–Emmett–Teller (BET) analysis. It was found that rGO increased the surface and short channels for the transfer of ions and electrons. The maximum capacitance of Co
3
O
4
/rGO was found to be 2870 F/g, while Co
3
O
4
/rGO/NF was observed to have the largest capacitance in the literature. Furthermore, rGO decreased resistance arising from charge and ion transfer by creating shorter channels. Therefore, the superior Co
3
O
4
/rGO/NF electrode in the tow-electrode system was investigated for asymmetric supercapacitor purposes. The rGO electrode served as the negative electrode, while the Co
3
O
4
/rGO/NF was assumed to be the positive electrode. A discharge time of 144 s led to a capacitance of 148 F/g, a power density of 486 W/kg, and an energy density of 20 Wh/kg.
The demands for alternative energy have led researchers to find effective electrocatalysts in fuel cells and increase the efficiency of existing materials. This study presents new nanocatalysts based ...on two binary transition metal oxides (BTMOs) and their hybrid with reduced graphene oxide for methanol oxidation. Characterization of the introduced three-component composite, including cobalt manganese oxide (MnCo2O4), nickel cobalt oxide (NiCo2O4), and reduced graphene oxide (rGO) in the form of MnCo2O4/NiCo2O4/rGO (MNR), was investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), and energy-dispersive X-ray (EDX) analyses. The alcohol oxidation capability of MnCo2O4/NiCo2O4 (MN) and MNR was evaluated in the methanol oxidation reaction (MOR) process. The crucial role of rGO in improving the electrocatalytic properties of catalysts stems from its large active surface area and high electrical conductivity. The alcohol oxidation tests of MN and MNR showed an adequate ability to oxidize methanol. The better performance of MNR was due to the synergistic effect of MnCo2O4/NiCo2O4 and rGO. MN and MNR nanocatalysts, with a maximum current density of 14.58 and 24.76 mA/cm2 and overvoltage of 0.6 and 0.58 V, as well as cyclic stability of 98.3% and 99.7% (at optimal methanol concentration/scan rate of 20 mV/S), respectively, can be promising and inexpensive options in the field of efficient nanocatalysts for use in methanol fuel cell anodes.
Multiwalled carbon nanotube–based magnetic nanoferrite-incorporated nanocomposites (metal oxide/MWCNT) were successfully produced via a simple hydrothermal technique. This research is aimed to ...investigate the structural and physical properties of Zn
0.5
Co
x
Mg
0.5−
x
Fe
2
O
4
/MWCNT (
x
= 0, 0.1, 0.2, 0.3, and 0.4) magnetic nanocomposite powders. Chemical bondings, phase and structural analyses, and surface morphology results were respectively investigated by using FTIR spectroscopy, XRD patterns, EDX, and FESEM micrographs. Optical band gap values of synthesized samples were obtained through the optical absorption diagrams extracted from ultraviolet–visible light (UV–Vis) spectroscopy. Moreover, magnetic properties and dye removal strength of various engineered nanopowders were evaluated by using VSM and UV–Vis apparatuses, respectively. The first novelty of this research is simultaneous incorporation of Zn, Mg, and Co into the spinel structure of iron oxide (magnetite) with different contents of cobalt. The other innovativeness of this research is exploring the manufactured nanocomposites’ abilities in industrial dyes’ removal and, importantly, studying the influence of cobalt content on dye removal intensity. It was concluded that amongst the synthesized specimens, the sample comprising 0.4 mol of Co benefits from the heftiest magnetic property and the most efficiency in methylene blue (MB) dye removal.
•A specific capacity of 1419 F/g was obtained for ZnFe2O4-rGO.•ZnFe2O4-rGO showed great capacitance retention of 93% after 5000 CV cycles.•ZnFe2O4-rGO electrode exhibited better supercapacitor ...performance than the ZnFe2O4 electrode.
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Binary transition metal oxides (BTMOs) are active materials, which have the potential for supercapacitor materials due to their high theoretical capacity. Herein, a BTMO based on zinc and iron was experimentally investigated in both the bare and hybrid forms, i.e. as ZnFe2O4 nanorods and ZnFe2O4 nanorods on reduced graphene oxide (rGO). After the synthesis, the products were investigated by different analytical techniques. The performance of the nano-engineered products as supercapacitor electrode materials were probed by electrochemical analysis. The electrochemical results obtained from the cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy showed the huge potential of the prepared electrodes for supercapacitor applications. The specific capacitance of ZnFe2O4-rGO was estimated as 1419 F/g with cyclic stability of 93% after 5000 successive voltammetry cycles at the scan rate of 10 mV/s. The electrochemical tests confirmed that the addition of rGO, owing to its large surface area and high electrical conductivity, improved the discharge time and cyclic stability besides increasing the specific conductance of the electrodes. The enhanced capacitance of the ZnFe2O4-rGO electrode recommends that the ion diffusion rate and the active redox site have been increased for capacitive behavior. Therefore, this composite can be a good candidate for energy storage.
In the current work, non-precious Nickel/Nickel oxide (Ni/NiO) and Ni/NiO/multi-walled carbon nanotube (Ni/NiO/MWCNT) composites were synthesized by combustion method for methanol oxidation. The ...fabricated catalysts were characterized by XRD, EDS, SEM, and TEM. From TEM micrographs, Ni/NiO with the particle size in the range of 20–30 nm was synthesized and uniformly embedded on MWCNTs with a diameter of 10–40 nm. It was found from the EIS results that the Ni/NiO/MWCNT has a lower charge transfer resistance than Ni/NiO, indicating a faster electron transfer from the Ni/NiO/MWCNT to methanol and faster reaction kinetics. The Ni/NiO/MWCNT catalyst showed a maximum peak current density of 15.94 mA cm−2 (49.81 mA mg−1) in peak potential of 0.43 mV (at room temperature) and long-term stability, showing good electrocatalytic activity. Also, DMFC single cell test based Ni/NiO/MWCNT anode catalyst showed a maximum power density of 41.8 mW cm−2, indicating its promising application in DMFC.
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•Non-precious electrocatalysts (Ni/NiO and Ni/NiO/MWCNT) were prepared.•The performance of catalysts in MOR was evaluated.•Ni/NiO/MWCNT indicated excellent electrocatalytic HER performance and long term stability.•Ni/NiO/MWCNT showed higher single-cell performance than Ni/NiO.•Ni/NiO/MWCNT catalyst is promising for DMFC application.
The structures containing iron and nickel can provide a unique platform for supercapacitor electrodes. In this research, the synthesis of iron and nickel nanoparticles and their hybrid with reduced ...graphene oxide (rGO) were performed. The samples were characterized with XRD analysis, SEM microscopy along with the EDS mapping, and TEM microscopy. The several electrochemical tests, i.e. cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), and electrochemical impedance spectroscopy (EIS) were performed to probe the applicability of materials as the supercapacitor electrode. The obtained results showed a fairly good capability of the NiFe/rGO hybrid for supercapacitor applications with a specific capacitance of 1224 F/g and discharge time of 351 s. Moreover, the cyclic stability of the electrode composed of both NiFe and rGO was enhanced up to 7%.
•NiFe/rGO hybrid composite was evaluated as supercapacitor materials.•An excellent specific capacity of 1224.2 F/g at a scan rate of 10 mV s−1.•Capacity retention of 89% for NiFe/rGO after 2000 cycles.
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A three-component nano-electrocatalyst, magnetite coated molybdenum disulfide hybridized with reduced graphene oxide (Fe3O4@MoS2/RGO), is synthesized by a two-step hydrothermal ...method. This catalyst is applied as an effective substitution for the platinum catalyst in methanol oxidation and hydrogen evolution reactions. Cyclic voltammetry, chronoamperometry, and linear sweep voltammetry are used to evaluate the performance of the electrocatalyst in acidic and basic media. The results of methanol oxidation reaction on the hybridized nano-electrocatalyst showed good electrocatalytic properties with considerable diffusion currents. This fact is confirmed by the Tafel plots and the calculated kinetic parameters of electron transfer. Fe3O4@MoS2/RGO showed an anodic transfer coefficient and exchange current of 0.464 and 4.80 × 10−8, respectively that are higher than Fe3O4/RGO. The presence of the porous MoS2 in catalyst has a key effect on supplying electroactive sites for electron transfer. Also, the high actual surface area obtained for the hybridized nano-electrocatalyst (A = 0.0295 cm2). The maximum power density of 35.03 mW cm−2 obtained for a single cell containing the prepared hybridized catalyst as the anode which shows a competitive feature of the synthetic catalyst compared to other reports. Furthermore, the synthetic catalyst shows the low-value overpotential of 108 mV and Tafel slope of 48 mV dec−1 during the hydrogen evolution process in acidic media. This is attributed to the synergistic effect between Fe3O4 and MoS2 and also increase the electron transfer rate due to adding conductive RGO to the catalyst. The results show that the synthetic nanocatalyst can have promising applications for hydrogen evolution and methanol oxidation reactions.
Designing and manufacturing active, sustainable, and affordable materials for hydrogen production and hydrogen evolution reaction (HER) is critical to the successful launch of hydrogen-based ...alternative energy technologies. Transition metal dichalcogenides such as molybdenum disulfide (MoS2), known as Pt-Like in the HER process, are considered as a suitable and inexpensive alternative to platinum. In this research, MoS2 was synthesized by hydrothermal method and then hybridized with carbonaceous materials such as reduced graphene oxide (rGO), hollow carbon nanosphere (HCNs), single-walled carbon nanotubes (SWCNTs), and multi-walled carbon nanotubes (MWCNTs). HER process in the presence of these hybrids, as catalysts, was studied. The results showed that the MoS2/rGO catalyst with a Tafel slope of 44mV dec−1 and an over-potential of 70mV is the most suitable catalyst. Also, MoS2/MWCNT with Tafel slope of 73mV dec−1 and 190mV over-potential showed a lower HER potential compared to other hybrids. It seems that the uniform dispersion of MoS2 nanoparticles on rGO increases both active sites and electrical conductivity than other carbonaceous materials, which leads to better results in HER process compared to other hybrid catalysts.
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•Hybrid catalysts based on MoS2 are prepared by hydrothermal method.•All Hybrid catalysts show improved HER performance than MoS2.•MoS2/rGO catalyst exhibits higher HER activity and stability than others.•The excellent electro-catalytic performance of MoS2/rGO is ascribed to conductivity and specific surface area of rGO.
This work used facile and novel methods to synthesize and fabricate ZnO-CNT@Fe3O4/NF as a supercapacitor electrode. The synthesis of active material and fabrication of electrodes performed by ...chemical vapor deposition (CVD) and Hydrothermal method. The carbon nanotube (CNT) was modified under the influence of nitrogen molecules in hot conditions using the CVD method. Through this method, the nitrogen molecules from the ammonia solution were deposited on CNT using a bubbler and maintained in the CVD apparatus under 700 °C heat conditions. To synthesize the active material, the modified CNT was decorated with Fe3O4 nanoparticles and composited with ZnO then the active material was coated on Ni Foam Through the hydrothermal method. To find the structure and morphology of the sample, the physical characterization was performed by Raman, XRD, SEM, EDX, TEM, and BET. The electrochemical properties of the electrodes were investigated by cyclic voltammetry (CV), galvanostatic charge-discharge analysis (GCD), and electrochemical impedance spectroscopy (EIS). The results showed that the ZnO-CNT@Fe3O4/Ni presented a specific capacitance of 532 F·g−1 at a scan rate of 10 mV·s−1 and excellent cycling stability of 88% capacitance retention during 3000 GCD cycles at 8 A·g−1.
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•Preparation of CNT by deposition of ammonia molecules by a CVD method•Synthesis and characterization of ZnO-CNT@Fe3O4 by hydrothermal method•Fabrication of ZnO-CNT@Fe3O4/Ni Foam as supercapacitor electrode•Study of ZnO-CNT@Fe3O4/NF electrode for supercapacitive applications•Capacitance and stability of ZnO-CNT@Fe3O4/NF during 3000 charge-discharge cycle
