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•Coupling of binary-phase TiO2 decreases particle size and increases specific surface area.•At TiO2/Bi2MoO6 heterojunction interface high separation of photocarriers was ...obtained.•TiO2/Bi2MoO6 exhibited a superior photocatalytic performance for different antibiotics degradation.
A series of binary-phase TiO2 modified Bi2MoO6 nanocrystals have been prepared via a solvothermal-calcination process. Trace TiO2 modification can effectively enhance the visible light catalytic activity of Bi2MoO6 to remove the antibiotics in aqueous solution. The obtained TiO2/Bi2MoO6 composites were investigated by some physicochemical techniques like XRD, N2 adsorption, SEM, TEM, UV–vis DRS, Raman, XPS, PL and Photo-electrochemical measurement. The presence of TiO2 nanoparticles (NPs) influenced the crystal growth of Bi2MoO6, decreasing the crystal size of Bi2MoO6 and effectively promoting its specific surface area. Moreover, the conduction band of TiO2 can serve as the electron transfer platform, which largely boosts the effective separation of photocarriers at TiO2/Bi2MoO6 heterojunction interface. With optimal TiO2 content (0.41 wt%), TiO2/Bi2MoO6 exhibited the best photocatalytic performance for different antibiotics degradation, e.g. ciprofloxacin, tetracycline and oxytetracyline hydrochloride under visible light irradiation. Moreover, the mechanism for enhanced photocatalytic performance in ciprofloxacin degradation was illuminated.
The novel electrochemical characteristics of graphene has been utilized in fuel cells as electrode additive, catalyst, bipolar plates and polymer electrolyte membrane. The analysis revealed that the ...durability and performance of fuel cells is improved by incorporating graphene.
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•Graphene is used as electrode additives, bipolar plate and polymer electrolyte membrane in fuel cells.•High stability is observed through graphene based bipolar plates fuel cell devices.•Graphene based electrolyte showed excellent ionic conductivity in polymer electrolyte membrane.
Novel and unique characteristics of graphene have received much attention in energy conversion and storage devices. Graphene based hybrid structures have been employed for a wide variety of efficient and durable fuel cell energy systems. Here, the review focuses on the components of fuel cell device and utilization of graphene in modern fuel cell technology such as graphene based electrodes, electro-catalysts, electrolyte membrane and bipolar plates. Dispersion of graphene over conductive electrodes provide electrochemically active sites to improve the electrocatalytic activity towards oxidation reduction reaction and fuel oxidation. The main issue regarding the degradation of fuel cell is corrosion of bipolar plates which is also discussed and can be reduced by incorporating graphene based metal composites. Various electrical transport measurements and electrochemical parameters were also studied to evaluate the fuel cell performance. Incorporation of graphene in fuel cell technology exhibit excellent catalytic performance in potential applications of fuel cell devices.
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•Chemical reactions were used for the synthesis of Ag nanosubstrates.•The SERS and Raman spectra were studied for the methimazole.•The correlation between the concentrations of ...methimazole and the SERS signal intensity was investigated.
An efficient method was developed for quantitative detection of methimazole using surface enhanced Raman spectroscopy (SERS). Silver nanoparticles (AgNPs) were prepared by a reduction method and designed as SERS substrates for the detection of methimazole, which is of medicinal importance. The morphology and the structure of the nanoparticles were characterized using a transmission electron microscope, a UV–vis spectroscopy, a Fourier transformed infrared spectroscopy and a Raman spectroscopy. The average size of the AgNPs was 60nm. The UV–vis spectrum showed a characteristic maximum absorbance at around 420nm for AgNPs. The adsorption behavior of methimazole on the AgNPs substrates was investigated by SERS and density functional theory (DFT) calculations. SERS experimental and theoretical results imply that a chemical interaction is considered between the NPs and methimazole. SERS experiments indicated an enhancement in the bands, which was utilized to develop a linear correlation between the methimazole concentrations and SERS signal intensity.
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•g-C3N4/TiO2 nanocomposites by in situ growth of TiO2 nanoparticles over 2D g-C3N4•Enhanced visible light photocatalytic activity of g-C3N4 in nanocomposite•Efficient separation of ...photogenerated charge carriers in nanocomposite
The visible light photocatalytic activity of graphitic carbon nitride, g-C3N4, can be enhanced by coupling with other semiconductors. In this work, mesoporous TiO2 nanoparticles were grown over g-C3N4 sheets resulting in the coupled nanocomposite photocatalyst. The morphological analyses using FE-SEM, TEM and AFM revealed the uniform deposition of TiO2 on g-C3N4 sheet. The visible light photocatalytic activity of g-C3N4 and g-C3N4/TiO2 composites were tested by methyl orange (MO) dye degradation and Cr(VI) reduction. The results revealed an enhancement in the visible light photocatalytic activity of g-C3N4 when it was coupled with TiO2 in the nanocomposite. Mesoporous TiO2 nanoparticles deposited over g-C3N4 provides the necessary large surface for the adsorption of the pollutant molecules. The enhanced visible light photocatalytic activity of g-C3N4 in the nanocomposite is due to the high surface area and efficient photogenerated charge carrier separation in the nanocomposite as evidenced in photoluminescence (PL) results.
•High-entropy carbides powders were synthesized by carbothermal reduction method.•The solid-solution elements have a great influence on EMW absorption capability.•The intrinsic characteristics make ...the high-entropy carbides promising EMW absorbing materials.
The electromagnetic wave absorption performance of high-entropy transition metal carbides, including (Ti0.2Zr0.2Hf0.2Nb0.2Ta0.2)C, (Ti0.2Zr0.2Mo0.2Nb0.2Ta0.2)C and (Ti0.2Zr0.2Cr0.2Nb0.2Ta0.2)C, was investigated in the frequency from 2 GHz to 18 GHz. The electromagnetic parameter measurement and subsequent electromagnetic wave absorption evaluation showed that the high-entropy transition metal carbides possessed good electromagnetic wave absorbing properties, which had a great relation to the solid-solution elements. The (Ti0.2Zr0.2Mo0.2Nb0.2Ta0.2)C with a 1.50 mm thickness displayed a minimal reflection loss of -32.1 dB, and the effective absorption bandwidth (<-10 dB) was in the frequency range of 13–18 GHz. Intriguingly, the minimum reflection loss reached -36.6 dB at the thickness of 2.50 mm. The electromagnetic wave absorption performance was mainly associated with conductivity loss and dipole polarization, which originated from intrinsic conductivity of the high-entropy carbides and lattice distortion resulting from solid solution of multiple elements, respectively. The experimental results show that the high-entropy transition metal carbides may be promising structural-functional integrated ceramics in wide applications.
The single-phase high-entropy transition metal carbide powders without complex structure and multi phases design present excellent EMW absorption properties, including minute reflection loss and broad absorption bandwidth.
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•Application of microcrystalline graphite in microwave absorbing materials.•Microcrystalline graphite/ZnFe2O4 were prepared by high-temperature ball milling.•Microcrystalline graphite/ZnFe2O4 showed ...reflection loss of −62.90 dB at 6.0 GHz.•Microwave absorption of composites originally from dielectric loss and magnetic loss.
Microcrystalline graphite (MG)/zinc ferrite (ZFO) composites were prepared by a high-temperature ball milling method. The magnetic and microwave absorption properties of MG/ZFO composites were analyzed in the frequency range of 2.0–18.0 GHz. The results showed that MG has a favorable impact on the microwave absorption capacity of ZFO. The composites containing 10 wt% MG had a minimum reflection loss of −62.90 dB, which is almost a factor of 12 higher than for pure ZFO, and their effective absorption bandwidth (EAB, RL<−10 dB) covers frequency range of 5.84–7.92 GHz for a matching thickness of 3.9 mm, and for a matching thickness of 1.8 mm, the EAB covers frequency range of 12.87–17.70 GHz. A probable mechanism of microwave absorption for MG/ZFO composites is based on a synergistic combination of dielectric and magnetic losses. The attractive properties of prepared composites indicate that they are promising and competitive materials for use in microwave absorption.
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•About 0.1 mol.% of Cr2O3 is optimal for the formation of the increased electrostatic double Schottky barriers height and thus an enhanced coefficient of nonlinearity α = 74 and a lower leakage ...current (IL < 0.2 μA/cm2).•Small amounts of added Cr2O3 primarily result in the formation of acceptor defects at the GBs for enhanced electrostatic Schottky barriers, which leads to an enhanced current-voltage (I-V) nonlinearity and a decrease of the leakage current.•For larger additions of Cr2O3 (above 0.20 mol.%) the Ca3(CrO4)2 phase starts to form, which led to a decreased barrier height and thus a decreased I-V nonlinearity with an α value of 25 and an increased leakage current (IL > 5 mA/cm2).
Novel ZnO-Cr2O3-based varistors can overcome the problems related to the volatile, high-cost and toxic components of conventional ZnO-Bi2O3-, ZnO-Pr6O11-, and ZnO-V2O5-based varistors. The influence of the varistor former with different doping levels, i.e., the Cr2O3, on the microstructure and electrical properties was examined and the optimal amount of Cr2O3 doping to enhance the electrical performance of ZnO-Cr2O3-based varistor ceramics was determined. The results showed that about 0.1 mol.% of Cr2O3 is optimal for the formation of the electrostatic double Schottky barriers with increased height at the grain boundaries (GBs) and thus an enhanced I-V nonlinearity (i.e., a coefficient of nonlinearity α = 73) and a lower leakage current (IL < 0.2 μA/cm2) in ZnO-Cr2O3-based varistor ceramics with an Eb of 383 V/mm. For larger additions of Cr2O3, a Ca3(CrO4)2 phase forms, which decreases the barrier height and leads to a lowering of α and an increase in IL.
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•Interlinked V2O5-PANI composites are synthesized by chemical polymerization.•V2O5-PANI exhibits the highest capacitance of 529.56 F g−1 with wide window of 1.6 V.•Correlation between ...electrochemical performances with IR peak shifts is studied.•Inorganic-organic synergistic effect plays crucial role for wide working window.•Asymmetric supercapacitor exhibits high energy and power in wide potential windows.
To meet the demand of high-energy density supercapacitors, development of suitable electrode material with a wide potential window and high specific capacitance is most important. In this report, we have synthesized V2O5-PANI nanocomposite through in-situ intercalation and polymerization reaction of aniline with V2O5, which shows a wide potential window as well as high specific capacitance. XRD, SEM and FTIR have been used to characterize the electrode materials. Their electrochemical activity and pseudocapacitive performances were investigated. The correlation between morphology and electrochemical performances were investigated which is a vital way for the selection of electrode materials. Due to the organic-inorganic compatibility, V2O5-PANI exhibits good electrochemical charge storage in a wide potential window of 1.6 V (ranging between −0.4 V to 1.2 V) with excellent stability of 84.2% capacitance retention after 5000 GCD cycles. Moreover, asymmetric supercapacitor was assembled V2O5-PANI composite and NiMn2O4 electrodes which yield remarkable energy and power density.
The zeolite X was synthesized from diatomite via hydrothermal method. The proposed crystallization mechanism is displayed in the following illustration. The intermediate species of zeolite X appears ...on the surface of solid particles. And the β cages build up the intermediate species, which was consist of four-membered rings (4R) and six-membered rings (6R). Then the β cages interconnect via double six-membered rings to form the framework of zeolite X.
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•The intermediate species of zeolite X appears on the surface of solid particles.•The β cages build up the intermediate species, which was consist of four-membered rings (4R) and six-membered rings (6R).•The double six-membered ring (D6R) played a critical role for the crystallization process.•The β cages interconnect via double six-membered rings to form the framework of zeolite X.
Here we systemically investigated the crystallization process of zeolite X using diatomite, a natural cost-effective silica precursor by the hydrothermal method. To decipher the mechanism, solids were separated from the mixtures at various stages of crystallization and were characterized by XRD, SEM, solid state NMR, FT-IR, UV-Raman and XRF. The XRD patterns revealed that the crystallization started between 3 and 3.5 h and ended by 5 h. The SEM images showed that the intermediate species of zeolite X appear on the surface of particles. The FT-IR and UV-Raman spectra suggested the presence of double six-membered rings (D6R) in the framework of zeolite X and they played a critical role in the crystallization process. Furthermore, the UV-Raman spectra indicated that the secondary building units of β cages formed the intermediate species and they were interconnected via double six-membered rings to form the framework of zeolite X.
•CaMoO4-based g-C3N4 composites were obtained with success by sonochemistry method.•CaMoO4-based g-C3N4 composites showed improvement in photodegradation capacity.•The mechanism of enhanced ...photocatalytic activity was investigated.
Herein, CaMoO4-based g-C3N4 composites are successfully synthesized by the sonochemistry method. All samples present photocatalytic activity under UV-light irradiation by employing methylene blue (MB). The structural analysis is available through X-ray diffraction (XRD), Raman, and FTIR spectroscopies, which verified a scheelite-type tetragonal structure for CaMoO4 with slight distortion in MoO4 clusters between samples and confirmation of g-C3N4 presence in the powder. FEG-SEM images reveal a higher formation of interfaces between CaMoO4 and g-C3N4 particles. Photoluminescence spectra are measured to study the photogenerated charge recombination process. Furthermore, the studies show that increased dosage of g-C3N4 onto the composite provides up to 95.1% of MB discoloration in 180 min, while CaMoO4 without g-C3N4 only provides 40.2%.
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