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.
Supercapacitors are very exclusive among energy‐storage devices for the wearable and portable industry. Due to simplicity, abundance occurrence, good electrical conductivity, and rich redox states, ...metal sulfides have a significant impact in supercapacitor applications in the present decade. Sulfur is the anion, associated with metal cations, and provides substantial tunable electrochemical, electrical, physical, and chemical properties in metal sulfides. In addition, carbonaceous materials enhance the electrochemical characteristics of metal sulfides synergistically for supercapacitors. Fast and scalable synthesis and fabrication of the supercapacitor cell with low‐cost metal sulfides and heterostructures should be developed to achieve the potential applications of these hybrid glorious materials. Herein, the significant and critical discussion of metal sulfides synthesis and their hybrid with carbon electrode structures for supercapacitor applications is disclosed. The realistic synthesis of metal sulfides, basic charge storage phenomena to elaborate the electrode nature, electrochemical properties including a single electrode, and asymmetric and symmetric cells are demonstrated for comparative purposes. The market values and application of supercapacitors are also elaborated. Herein, a better understanding to fresh readers about metal sulfide hybrid electrode structures for supercapacitors is provided.
Due to their simple synthesis, good electrical conductivity, and multiredox states, metal sulfide electrode structures have a great impact in supercapacitor applications. Herein, a good chance to the fresh reader to understand supercapacitors as well as good ideas for experts to elucidate metal sulfide‐secured carbon materials for supercapacitors is provided.
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.
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.
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).
•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.
Carbon-based materials are mostly used in supercapacitor due to control porosity, higher surface area, and easy processing for electrode production. However, it is still challenging to fabricate ...carbon/metal oxide-based nanocomposite electrodes with various structures and configurations for supercapacitors, particularly for miniaturized electronics. Here, in the present study, CeO
2
–Nd
2
O
3
/rGO ternary nanocomposite was synthesized by facial co-precipitation route, which evident enhanced capacitive performance than CeO
2
–Nd
2
O
3
binary composite, bare CeO
2,
and Nd
2
O
3
. The rGO was homogeneously anchored on the surface of CeO
2
–Nd
2
O
3
nanoparticles, forming a semi-spherical morphology. The electrochemical performance of all electrodes was investigated by different measurements. The ternary composite have a higher specific capacitance of 1265 F g
−1
at 3 A g
−1
current density and maintained 99% retention after 2000th cycles, showing excellent cycling performance and rate capability compared to other grown products. The excellent electrochemical pseudocapacitive performance of the ternary composite-based electrode could be ascribed due to rGO and its interfacial contact with CeO
2
–Nd
2
O
3
. The improved electrode conductivity generates plentiful active sites for charging and discharging and provides an easy path for the fast transportation of ions. These results open an innovative pathway for fabricating rGO and metal oxide-based composite in developing electrochemical energy storage devices for commercial production.
Graphical abstract
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).