Calcium substituted strontium hexaferrite Ca
x
Sr
1−
x
Fe
12O
19 (
x=0.0−0.6) nanoparticles are synthesized by chemical co-precipitation method. The synthesized samples are characterized by Fourier ...Transform Infrared (FTIR), X-ray diffraction (XRD), Scanning Electron Microscopy, Transmission Electron Microscopy, DC electrical resistivity and dielectric measurements. FTIR data of uncalcined sample shows that nitrate ions are present which disappeared on calcination at 920
°C. The XRD data shows that a single hexagonal magnetoplumbite phase is formed in samples in which the calcium content,
x, is ≤0.20. However, a nonmagnetic phase (α-Fe
2O
3) in addition to the hexagonal phase is also present in samples with
x>0.20. The average crystallite size is found between 17 and 29
nm. The DC electrical resistivity increases with increase of calcium content up to level of
x=0.2 but decreased on further addition of calcium. The enhanced resistivity of the calcium doped material has potential applications in microwave devices. The variations of dielectric constant and dielectric loss angle are explained on the basis of Maxwell–Wagner and Koops models.
SnS2/ZnTe nanocomposites were successfully synthesized via a two-step methodology incorporating hydrothermal techniques. The resultant nanocomposites underwent comprehensive characterization ...encompassing morphological, structural, and compositional aspects through the utilization of scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). Furthermore, the electrochemical performance of these newly synthesized nanostructures was evaluated in the absence and presence of light to ascertain their suitability for energy generation applications. In the context of the hydrogen evolution reaction (HER) against reference electrode 0.185 vs. RHE, it was observed that SnS2/ZnTe electrodes exhibited notably low overpotentials, registering at 185 mV, along with a Tafel slope of 80 mV dec−1 under visible light. These findings underscore the superior catalytic activity of SnS2/ZnTe electrodes in the HER. Moreover, the SnS2/ZnTe electrode demonstrated a substantially reduced overpotential of 105 mV at a current density of 10 mA cm−2, accompanied by a Tafel slope of 47 mV dec−1 under visible light, indicative of a swift and efficient performance in the oxygen evolution reaction (OER). In light of these outcomes, these nanostructures exhibit significant promise as electrode materials for applications in water splitting, thereby contributing to advancements in sustainable energy production.
•CuAl2O4/rGO nanohybrid was prepared by facile hydrothermal approach.•Several analytical tools were employed to identify material characteristics.•CuAl2O4/rGO nanohybrid display high specific ...capacitance and energy density of 1206 F/g and 34.83 Wh kg−1, respectively.•The fascinated electrochemical results were attributed to greater electronic conductivity, faster charge transfer and enriched active sites.
Transition metal-based spinel oxides are fascinating supercapacitor electrodes materials due to their good specific capacitance (Cs) and cost-effectiveness. But the spinel materials show poor cycling stability due to their limited surface area. This issue was reduced by using carbon-based electrode materials such as rGO, which enhances the electroactive surface area that leads to improve the number of reactive sites. In this research, a simple hydrothermal approach was utilised to synthesise the CuAl2O4/rGO (CAO/rGO) nanocomposite. It successively characterised with different analytical techniques to study the physiochemical property of the synthesized materials. Additionally, the potential of the materials as the electrode was determined with a three-electrode configuration by utilising different electrochemical tools that were performed to assess the characteristics of the electrode material. The synthesised nanocomposite exhibits a magnificent specific capacitance (Cs) of 1206.14 F/g at 1 A/g, while demonstrating specific energy (Ed) of 34.83 Wh kg−1 and specific power (Pd) of 228 W kg−1 which is higher than individuals and also shows high retention capacitance value of 93.36% after 8000th charge/discharge (GCD) cycles. The symmetric behaviour of the fabricated electrode is also determined with two electrode systems exhibiting the specific energy and specific capacitance of 16.54 Wh kg−1 and 601.91 F/g, correspondingly. This study demonstrates that incorporating rGO into CuAl2O4 nanoarray improves energy storage performance and it has the potential to work in other energy storage devices.
The magnetic and electrical behavior of SrZr
x
Cu
x
Fe
12−2
x
O
19 (where
x
=
0.0–0.8) hexaferrite nanoparticles are reported in this paper. Five samples were synthesized by the chemical ...co-precipitation method. SrFe
12O
19 is a semiconductor however doping Zr
x
Cu
x
at iron sites resulted in a semiconductor-metal transition at a temperature
T
M–S. The structural parameters of the samples were obtained by FTIR, XRD, EDX, SEM and TEM analyses. The FTIR spectrum and XRD pattern of the samples showed that the synthesized materials were of a single phase. The particle size was in the range 26–37
nm as estimated by Scherrer formula, which is comparable with the values estimated from SEM (40–80
nm) and TEM (30–60
nm) analyses. AC magnetic susceptibility and DC electrical resistivity measurements were carried out in a temperature range 300–800
K. The Curie temperature (
T
C) decreases on substitution of Zr–Cu. A significant increase in the room temperature resistivity is noted with the addition of Zr–Cu up to
x
≤
0.4. The drift mobility (
μ
d) and the activation energy (Δ
E) are also calculated from electrical resistivity data. The variation of the dielectric constant (
ɛ′) and the dielectric loss factor (tan
δ) with frequency in the range 80
Hz–1
MHz and composition of the sample is observed.
Electrochemical water splitting is economically unviable due to the sluggish kinetics of the anodically uphill oxygen evolution reaction (OER). This is directly linked to the design and facile ...fabrication of low overpotential water oxidation electrocatalytic materials, engaging applied methods and earth-abundant precursors. Here, we demonstrate facilely synthesized ZnTe nanospheres (ZnTe-NS) as an efficient and durable OER electrocatalyst, executing water oxidation with a much lower energy cost relative to other previously reported non-noble metal-based catalytic systems. The catalytic system shows excellent performance, initiating the oxygen evolution reaction at just 1.41 V
vs
. RHE (
η
= 180 mV) and reaching current densities of 10 mA cm
−2
and 100 mA cm
−2
at 1.44 V
vs.
RHE (
η
= 210 mV) and 1.63 V
vs.
RHE (
η
= 400 mV), respectively; this performance is superior to state-of-the-art RuO
2
and IrO
2
catalysts reported previously. Furthermore, a modest Tafel slope of 62 mV dec
−1
, indicative of a one electron and one proton transfer mechanism, and a large TOF of 0.25 s
−1
at just
η
= 210 mV are achieved. The catalyst advantageously exhibits a stable current density of >50 mA cm
−2
for more than 24 hours during water electrolysis experiments for extended time periods. The hydrothermally developed ZnTe-NS are 150-200 nm in size and display hollow structures, as evaluated
via
high-resolution transmission electron microscopy. XRD and XPS techniques are employed to confirm the formation of ZnTe-NS. DFT calculations show that hydroxyl attachment energy is very favorable on the highly porous and crystalline ZnTe-NS, further confirming their remarkable properties for enhanced electrocatalytic OER activity. This study demonstrates valuable insights into developing the first example of a highly durable Zn chalcogenide, more specifically ZnTe-NS, as an efficient and inexpensive electrocatalyst material for water oxidation. Through an easily accessible synthesis method, ZnTe-NS maintain their integrity, morphology and chemical structure, even after many hours of continuous water electrolysis.
Electrochemical water splitting is economically unviable due to the sluggish kinetics of the anodically uphill oxygen evolution reaction (OER).
•Particle size of these samples is suitable for high density recording media.•The samples have coercivity suitable for longitudinal magnetic recording media.•The sample (x=0.8) has dielectric ...constant useful for high frequency applications.
Zirconium copper substituted calcium strontium hexagonal ferrites with composition Ca0.5Sr0.5Fe12−2xZrxCuxO19 (x=0.0, 0.2, 0.4, 0.6, 0.8) have been synthesized by the chemical co precipitation procedure. These compounds were characterized by X-ray diffraction, thermogravimetry and scanning electron microscopy. Dielectric and magnetic properties of these hexaferrites were also explored. XRD analysis confirmed the single hexagonal phase of all the compounds and the average crystallite size was between 37 and 47nm. The dielectric parameters show relaxation behaviour at higher frequencies. The values of dielectric parameters increase with dopants. In the range of magnetic field studied, the saturation magnetization decreases as the dopant contents increase which may be due to the nonmagnetic character of the substituents. The coercivity of the Zr–Cu doped derivatives of strontium calcium hexaferrites is increased up to x=0.2 and then decreased. The values of coercivity are above 600Oe which make them suitable materials for use in industries in longitudinal magnetic recording media.
•ZnO/ZnSe heterostructures were synthesized successfully via one-pot hydrothermal approach.•The synthesized heterostructure photocatalysts have been employed for the degradation of Congo Red.•The ...higher photocatalytic activities are ascribed to efficient charge separation.
Environmental remediation using sunlight is one of the most promising and cost-effective approaches to mitigate environmental hazards significantly related to the industrial development. In the present work, we report the synthesis of ZnO/ZnSe heterostructure via one-pot hydrothermal approach for the photocatalytic degradation of diazo dye i.e. Congo red. XRD analysis verified the crystal structure, phase purity and successful synthesis of the ZnO/ZnSe heterostructure photocatalysts. Moreover, the morphology and elemental composition of the photocatalysts were studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron dispersive X-ray spectroscopy (EDX), respectively. The alignment of energy levels for the synthesized heterostructured photocatalysts was also drawn while using UV-visible diffuse reflectance spectroscopy (DRS) and X-ray photoelectron spectroscopy (XPS). Finally, the as-synthesized heterostructures were employed as efficient photocatalysts for the degradation of Congo red under the illumination of UV-visible light. Our results indicated that ZnO/ZnSe heterostructure photocatalysts with maximum ZnSe content can efficiently degrade the dye up to 91% which might be attributed to the effective charge separation as extended solar absorption due to narrow bandgap of ZnSe.
Environmental degradation and energy shortage are the two biggest problems facing the world right now. Because of the limited supply of non-renewable sources, the production of environment-friendly ...energy and its storage has gained significant importance. Pseudocapacitors have lately caught the interest of energy specialists due to their greater energy/power density and prolonged cycle life. In this work, binding-free SnTe/SnSe (STSS) electrodes deposited onto Ni foam (NF) as the conductive substrate have been developed by a facile hydrothermal route for supercapacitor applications. Several analytical tools were utilized to study the morphological, structural and textural characteristics. The electrochemical results obtained from a three-electrode system suggest that the STSS electrode material exhibits great specific capacitance (
) of 1276 F g
, specific energy (
) of 46.45 W h kg
and specific power (
) of 256 W kg
@ 1 A g
. The results of
indicate that the STSS (31.28 mF) has a larger
value than those of SnTe (23.22 mF) and SnSe (26.35 mF). The analysis of electrochemical stability indicates that the STSS displays structural stability over 5000 cycles with a maximum capacitance retention of 96%. The Nyquist plot profile displayed a smaller
value for STSS (0.89 Ω) than SnSe (1.13 Ω) and SnTe (1.97 Ω). The symmetric behavior of STSS was determined in 2.0 M potassium hydroxide. The results reveal that this material has a specific capacitance of 537.72 F g
and specific energy of 78.32 W h kg
. These findings suggest that the STSS electrode might serve as a potential candidate for supercapacitors and other energy-saving equipment.
The sol-gel auto-combustion method was adopted to synthesize nanomaterials of single-phase X-type hexagonal ferrites with the composition of Sr2-xGdxNi2Fe28-yCdyO46（x=0.00,0.02,0.04,0.06,0.08,0.10 ...and y = 0,0.1,0.2,0.3,0.4,0.5）.The structural properties were carried out by XRD analysis and the lattice parameters show variation with the doping of Gd-Cd.The average particle size measured by TEM was in the range of 8-10 nm which is beneficial in obtaining suitable signal-to-noise ratio in recording media and biomedical applications.The room temperature resistivity enhanced with the increase of the dopant concentration.The increase in resistivity indicates that the synthesized materials can be considered good for the formation of the multilayer chip inductors（MLCIs） as well as for the reduction of eddy current losses.The dielectric constant decreased with the increase in the frequency which is the general reported trend of the hexagonal ferrites and can be explained on the basis of Koop’s theory and Maxwell-Wagner polarization-model.The abnormal dielectric behavior indicates the formation of small polarons in the material.The maximum value of tangent loss at low frequencies reflects the application of these materials in medium frequency devices（MF）.
Strontium hexaferrite nanoparticles substituted with bismuth and chromium having nominal composition SrFe12−2xBixCrxO19 (x=0.2, 0.4, 0.6, 0.8) have been synthesized by the sol–gel method. The samples ...are characterized by X-ray diffraction (XRD), Fourier Transform Infrared (FTIR), DC electrical resistivity, magnetic and dielectric measurements. The XRD data shows that the nanoparticles are crystallized into single hexagonal magnetoplumbite phase. Room temperature DC electrical resistivity decreases on increasing the Bi–Cr contents. The dielectric constant, dielectric loss and tangent loss decrease with the frequency. The magnetic properties such as saturation magnetization (Ms), remanence (Mr) and coercivity (Hc) increase with increasing the dopant concentration up to x=0.2 and then decrease with further increase in dopant content. Coercivity decreases with increasing the dopant content up to x=0.2 then increases with further increase in dopant content. The increase in Ms and Mr while decrease in Hc indicates that the material with composition SrBi0.2Cr0.2Fe11.6O19 is suitable for magnetic recording media.
•Sol–gel method has been employed for the synthesis of single phase hexaferrites nanomaterials.•Dielectric parameters show some relaxation behavior at high frequencies.•We are able to improve the saturation magnetization and remanence.•The synthesized materials are beneficial for recording media.
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