TmVO4/Fe2O3 nanocomposites: Sonochemical synthesis,characterization, and investigation of photocatalytic activity

Today, a unique method of treating environmental contaminants is drawing considerable attention. Organic dyes are significant wastes from myriad industries, including paper, food, and textiles, which have become a serious environmental concern and have the potential to be toxic to humans and living organisms. This study demonstrates the fabrication and characterization of thulium vanadate (TmVO₄) nanostructures and TmVO₄/Fe₂O₃ nanocomposites that were effectively applied in the photodecomposition efficiency of cationic and anionic organic contaminants. The TmVO₄/Fe₂O₃ nanocomposites were prepared through a sonochemical method, and triethylenetetramine (TETA) was employed as a precipitating and capping agent. The tests were performed using a probe as a sonication source (60 W, 18 kHz). The impact of TmVO₄ content (5, 10, 15, and 30%) on the modification of binary nanocomposites was studied in terms of morphological, optical, and photocatalytic properties. The recyclable magnetic TmVO₄/Fe₂O₃ nanocomposites with 15% TmVO₄ achieve 68.3% of eriochrome black t (EBT) utilizing visible origin. More notably, the binary TmVO₄/Fe₂O₃ nanocomposites reveal higher photocatalytic activity than the pure TmVO₄ and Fe₂O₃ nanoparticles.     

Using pomegranate peel powders as a new capping agent for synthesis of CuO/ZnO/Al2O3 nanostructures; enhancement of visible light photocatalytic activity

CuO/ZnO/Al₂O₃ (CZA) nanoclusters were successfully synthesized via a facial and green method in the presence of pomegranate. The structural analysis of the samples confirmed the formation of CZO nanostructures in the range of 14–17 nm. The morphological studies of the samples indicated that, the shape and the particle size of the CZO nanoclusters depend on the sources, ratio of the cationic sources, time and heating temperature. The photocatalytic properties of the CZO nanostructures were obtained using photooxidation of azo dyes; Methyl orange, Methylene blue and Methyl red. The photocatalytic activity of the sample shows about 85% of azo dyes degradation after 75 min of visible light irradiations. The results were clearly demonstrated that the pure CZA nanoparticles can be used as a potential photocatalyst under visible lights for removal of contaminants.     

Li2MnO3/LiMnBO3/MnFe2O4 ternary nanocomposites: Pechini synthesis,characterization and photocatalytic performance

Li₂MnO₃/LiMnBO₃/MnFe₂O₄ ternary nanocomposites were synthesized via modified pechini sol-gel approach employing the mixture of metal cations, boric acid, ethylene glycol and ethylene diamine tetra acetic acid gelating agent. Shape and size of nanocomposites was controlled by changing molar ratio of metal ions, ethylene glycol and gelating agent. In order to confirmation of crystalline and structural features of products, analyses of X-ray diffraction, Fourier transform infrared and energy dispersive X-ray were carried out. Scanning electron microscopy and transmission electron microscopy images were taken for morphology investigation of nanostructure products. Band-gap of ternary nanocomposites calculated by UV–Vis data is 2.6 eV. Magnetic property of Li₂MnO₃/LiMnBO₃/MnFe₂O₄ ternary nanocomposites investigated through vibrating sample magnetometer presents ferromagnetic behavior. Moreover, photocatalytic activity of Li₂MnO₃/LiMnBO₃/MnFe₂O₄ and Li₂MnO₃/LiMnBO₃ nanocomposites was investigated in aqueous solution via UV and visible light for degradation acid red 88 dye. Some effective parameters such as dye concentration, irradiation and nanocomposite type were evaluated for optimum removal of water pollutant dye.     

Sonochemistry fabrication of Er2Sn2O7 nanoparticles with advanced photocatalytic performance of their carbonic nanocomposites

The insufficiency of clean water sources has become a perilous tension for the future of the world that one of the eco-friendly and cost-effective solutions is the photocatalytic process for removal of artificial dyes and poisonous organic impurities. In the current research, a simple sonochemistry process was accomplished to gain Er₂Sn₂O₇ (ESO) nanoparticles with progressive photo-catalytic proficiency. Various surfactants of cationic Cetyl Trimethyl Ammonium Bromide (CTAB), anionic Sodium dodecyl sulfate (SDS) and polymeric polyethylene glycol 6000 (PEG 6000) were utilized to the creation of pure Er₂Sn₂O₇ nanoparticles. The figure and dimension of products were studied by various characterization procedures of spectroscopic and microscopic. The photo-degradation performances of the pure Er₂Sn₂O₇ nanoparticles prepared in different conditions were tested to remove of diverse synthetic dyes. Carbon-based nanocomposites of graphitic carbon nitrides (g-C₃N₄), graphene quantum dots (GQDs) and graphene oxide (GO) present enhanced photocatalytic activities. The outcome of the catalyst size, type of dye, kind of carbon structure and scavenger kind was labeled on modifying ability of Er–Sn–O nano-catalyst task. Optimized Er₂Sn₂O₇/g-C₃N₄ nanocomposites have an efficiency of 93.9% for degradation of acid red dye that OH radicals support photo-degradation of contamination.     

Magnetically recyclable ZnCo2O4/Co3O4 nano-photocatalyst: Green combustion preparation,characterization and its application for enhanced degradation of contaminated water under sunlight

Finding the appropriate photocatalyst for elimination of organic contaminants is a challenge for remediation of environment. Herein, we tried to synthesis of ZnCo₂O₄/Co₃O₄ nanocomposite using the Stevia extract as a natural reagent that can act as green fuel in auto-combustion sol-gel method and control the size of product by steric-hindrance induced by its structure. The chelating role of this natural reagent was investigated by changing the amount of this extract for synthesis of different samples. Analyses confirmed the effect of this parameter on morphology and size of products. The photocatalytic activities of different samples under visible irradiation were investigated and the effect of size of photocatalyst on degradation percent of dye was studied. The good performance of ZnCo₂O₄/Co₃O₄ nanocomposite was detected by degradation of Acid violet 7 about 93.5% in 70 min and 2-phenol about 100% in 18 min. Photocatalyst was easily recycled through magnetic properties of products and stability of it under irradiation was confirmed by degradation of dye after 10 times recycling.     

The preparation and characterization of CdS1−xTex semiconductor films for hydrogen production by the chemical bath deposition method

Te-doped CdS semiconductor films were fabricated on indium-tin-oxide (ITO) substrates by chemical bath deposition. The chemical composition, morphology, crystalline, and optical properties of the Te-doped CdS films were characterized by XPS, SEM, XRD, UV-vis, and Ellipsometer. Additionally, the carrier density and flat-band potential of the semiconductor electrodes were measured by Hall and potentiostat. Results show that the electrical property of Te-doped CdS films was changed from n-type to p-type semiconductors, when the molar ratios of Te in the bath solution were higher than 0.4. Besides, energy band-gap and carrier densities of the Te-doped samples were found in the range of 1.85-2.33 eV and 9.68×10¹⁵-1.56×10¹⁷ cm⁻³, respectively. Furthermore, the maximum photocurrent density of the samples was found to be −0.81 mA/cm² (under the external potential of −1.0 V) with the largest hydrogen production capability of 1.29 ml/cm², when illuminated under a 150 W Xe lamp.     

Sono-synthesis and characterization of Ho2O3 nanostructures via a new precipitation way for photocatalytic degradation improvement of erythrosine

For the first time, Ho₂O₃ nanostructures have been successfully produced through a facile sonochemical way. In this way, diethylenetriamine (dien) as a new precipitator and holmium nitrate were employed to fabricate Ho₂O₃ products. To optimize the grain size, morphology and photocatalytic efficiency of Ho₂O₃ samples, the kind of capping agents has been changed. The formed Ho₂O₃ products have been characterized by means of FT-IR, TEM, EDX, XRD, FESEM and DRS. It was observed that the grain size, morphology and photocatalytic efficiency of the sonochemically produced Ho₂O₃ were largely dependent on the kind of capping agent. The photocatalytic behaviors of Ho₂O₃ nano and bulk structures have been compared through decomposition of erythrosine contaminant under ultraviolet irradiation.     

Synthesis and photo-catalytic activity of porous g-C3N4: Promotion effect of nitrogen vacancy in H2 evolution and pollutant degradation reactions

Different density nitrogen vacancy modified g-C₃N₄ photocatalysts were successfully prepared, and investigated their photocatalytic performance for H₂ evolution and pollutant degradation. In this system, the increase of nitrogen vacancy density could enable the conduction band position of resultant g-C₃N₄ to negative shift compared to previous g-C₃N₄. Meanwhile, various positive factors were also introduced in this system, such as larger surface areas, the improvement of light response capacity, effective separation of photogenerated charge, resulting in resultant g-C₃N₄ photocatalysts exhibiting evident improvement of photocatalytic performance for H₂ evolution and pollutant degradation. Obviously, this work provides physico-chemical insights for the nature of the promotion effect of nitrogen vacancies.     

Synthesis and characterization of nanoporous ZnO and Pt/ZnO thin films for dye degradation and water splitting applications

In this paper, nanoporous ZnO and Pt/ZnO films were synthesized by a combination of simple spray pyrolysis and DC sputtering techniques at different flow rates and deposition times. X-ray diffraction, contact angle, and spectrophotometric measurements showed the growth of hexagonal ZnO Wurtzite phase with hydrophilic nature and high transparency in the visible region. By sputtering Pt nanoparticles on ZnO surfaces, the absorption edge is redshifted from UV region to the visible light region. The optical band gap of Pt/ZnO films is decreased from 3.74 to 1.86 eV as the deposition time increased to 4 min. The Pt/ZnO films exhibited higher photocatalytic activity and stability than pure ZnO films for methylene blue photodegradation. From the photoelectrochemical water splitting measurements, the current density of 4 min Pt/ZnO film is one hundred times greater than the value of pure ZnO film. The incident photon-to-current conversion efficiency at 470 nm was for the first time 76.2%.     

Preparation and characterization of o-LiMnO2 cathode materials

Small particle-sized orthorhombic LiMnO₂ powders were prepared via Pechini's route with Li/Mn molar ratio ranging between 1.00 and 1.20, followed by calcinations at 300 °C in air and heat-treatment at temperatures between 700 and 900 °C for various durations under flowing nitrogen. The effects of heat-treatment conditions and starting Li/Mn molar ratio on the crystalline structure and the electrochemical properties were investigated with XRD, SEM, and capacity retention study. Orthorhombic phase were found exclusively in the samples prepared with starting Li/Mn molar ratios between 1.00 and 1.05 followed by heat-treatment at 800 °C for 15 h, whereas monoclinic Li₂MnO₃ and tetragonal Li₂Mn₂O₄ were also observed in the samples prepared with Li/Mn ratios higher than 1.10. The charge/discharge curves of capacity retention studies and the cyclic voltammograms showed that the transformation of o-LiMnO₂ into cycle-induced spinel phase proceeds more progressively and the capacity loss upon cycling are more significant for the samples containing the impurity phases than the well-ordered o-LiMnO₂ sample. The sample synthesized with starting Li/Mn ratio of 1.05 followed by heat treatment at 800 °C for 15 h showed the most promising cycling performance among the prepared powders with the maximum discharge capacity of 158 mAh g⁻¹ at 20th cycle and capacity loss of 3% between 20th and 80th cycles at 30 °C.     

Hydrothermal synthesis of CuMn2O4/CuO nanocomposite without capping agent and study its photocatalytic activity for elimination of dye pollution

The problem of water pollution is a great concern. Elimination of dye pollution from the solvent phase by adsorption is a necessary aspect of research. In this work, Cu-based spinel nanocomposites were synthesized without using any surfactant, via a hydrothermal method at 180 °C for 12 h, they can help us to solve the waste disposal problem. The Cu (II) and Mn (II) nitrates with a stoichiometry ratio of 1:2 were used as precursors. This method involves the hydrolysis of Mn and Cu salts in aqueous solution using ammonia as a pH regulator. In order to optimization the morphology and structural characterization of the nanocomposites, effects of the reaction time and temperature were investigated. XRD patterns confirmed formation CuMn₂O₄/CuO nanocomposites. VSM showed an antiferromagnetic behavior for the nanocomposites in high fields. It is due to the super exchange interactions between the Mn ions. Also, VSM displayed a moderate ferromagnetic behavior with a coercivity of 134 Oe in low fields. The photocatalytic performance of the nanocomposites was examined against the organic dyes of malachite green, eriochrome black T, and methyl orange. CMO NCs exhibited their higher photocatalytic activity in the presence of 0.07 g CMO NC for the degradation of MG solution with 10 ppm concentration. MG contaminant photodegradation was 73.27% after 90 min in this condition.     

Novel FeVO4/CuS heterojunction nanocomposite as a high-performance visible-light-active photocatalyst for ibuprofen degradation in aquatic media

Herein, we report the fabrication of type-II FeVO₄/CuS heterojunction nanocomposite by a versatile reflux-assisted co-precipitation procedure. The hybrid FeVO₄/CuS heterostructure with a band gap of 1.95 eV, demonstrated excellent degradation efficiency of ibuprofen antibiotic (～95%) after 90 min of visible-light irradiation, which displayed remarkably enhanced photocatalytic degradation (1.75 fold higher) in comparison to pristine FeVO₄ structure. The superior photocatalytic performance of the FeVO₄/CuS nanocomposite is associated with hierarchical flower-like architectures, great visible-light harvesting, and poor electron-hole recombination due to the fabrication of type-II heterojunction. In addition, we introduced an obvious photocatalytic destruction mechanism, which indicated that superoxides (^?O₂^?) and holes (h⁺) were the invasive species in antibiotic degradation on the FeVO₄/CuS photocatalyst. Consequently, the as-prepared FeVO₄/CuS heterojunction photocatalyst is a promising candidate for the development of future photocatalysts towards the elimination of antibiotics under sun light irradiation at short process time.     

Flower-shaped magnetically recyclable ZnS/ZnIn2S4/Fe2O3 nanocomposites towards decolorization of colored pollutants

Innovation the photocatalysts with acceptable performance, and facile recycle ability with magnetic separation is one of the most important challenges for researchers because of they are the promising materials can help to environmental health. Fe₂O₃ nanostructures with different ration loaded on ZnS/ZnIn₂S₄ nanocomposite were efficaciously provided through glycothermal procedure. The effect of amount of Fe₂O₃ nanostructures on structural, physical, magnetic and photocatalytic attributes of the resultant nanocomposite was explored. Morphology, uniformity and size of magnetic recyclable photocatalysts were detected, and present a flower shaped microstructures with assembling the nanosheets. Based on magnetic hysteresis, ternary ZnS/ZnIn₂S₄/Fe₂O₃ nanocomposite exposed the maximum saturation magnetization of 0.5481 emu/g which is higher than binary ZnS/ZnIn₂S₄ nanocomposite. Photocatalytic decolorization of ZnS/ZnIn₂S₄/Fe₂O₃ nanocomposites was conducted in Rhodamine B (RhB) and Methyl orange (MO) solutions illuminated under a 400 W Osram lamp. The outcomes discovered that 95.07% and 56.42% of RhB and MO was removed for the ZnS/ZnIn₂S₄/Fe₂O₃ nanocomposites with ratio of 1:1 from Fe₂O₃:Zn. Moreover, it can be simply separated and recycled after being used five times and the degradation efficiency remains 60.83%. Compared to the other catalysts, the magnetic ZnS/ZnIn₂S₄/Fe₂O₃ nanocomposites is suitable for large scale requests in industrial water treatment system.     

Preparation, characterization and application of Pt-Ru-Sn/C trimetallic electrocatalysts for ethanol oxidation in direct fuel cell

This work aimed to develop a method for the preparation of carbon-supported platinum nanocatalysts modified with Ruthenium and Tin, which were then evaluated for ethanol eletrooxidation in direct fuel cells. The Pechini method was employed to obtain these catalysts. This method consists in the decomposition of a polymeric precursor of metal salts. Nanocatalysts containing different Pt/Ru/Sn molar ratios were prepared by keeping the carbon/metal ratio at a constant value of 60/40%. The obtained nanoparticles were physico-chemically characterized by X-ray Diffraction (XRD), Transmission Electron Microscopy (TEM), and Energy Dispersive X-ray Spectroscopy (EDX). Crystallite size of around 7.0 nm and 5.8 nm were achieved for the bimetallic and trimetallic nanocatalysts, respectively. The experimental composition was close to the nominal one, but the metal particles were not evenly distributed on the carbon surface. Electrochemical characterization of the nanoparticles was accomplished by cyclic voltammetry (CV) and chronoamperometry. High Performance Liquid Chromatography (HPLC) was carried out after ethanol electrolysis for determining the products generated. Acetaldehyde was the main electrolysis product and traces of CO₂ and acetic acid were also detected. Addition of Ru and Sn to the pure Pt nanoelectrocatalyst significantly improved its performance in ethanol oxidation. The onset potential for ethanol electrooxidation was 0.2 V vs. RHE, in the case of the trimetallic nanocatalyst Pt_0.8Ru_0.1Sn_0.1/C, which was lower than that obtained for the pure Pt catalyst (0.45 V vs. RHE).     

Band gap of C3N4 in the GW approximation

Ab initio calculations based on density functional theory are performed to study the stability of newly proposed C₃N₄ forms. Heptazine-based g-C₃N₄ was found to be energetically favored relative to other phases. The quasiparticle band energies of different C₃N₄ phases are calculated using the GW method. Among the seven phases of C₃N₄ studied, only the pseudocubic phase and g-h-triazine phase have direct band gaps, and all of the other phases have indirect band gaps. The band gap of α-C₃N₄, β-C₃N₄, cubic-C₃N₄, pseudocubic-C₃N₄, g-h-triazine, g-o-triazine and g-h-heptazine is 5.49 eV, 4.85 eV, 4.30 eV, 4.13 eV, 2.97 eV, 0.93 eV and 2.88 eV, respectively. From the viewpoint of band gap energies, both the g-h-heptazine and the g-h-triazine phases can be used as suitable photocatalysts for hydrogen production using water.     

Synthesis,characterization and photocatalytic performances of Cu2MoS4

A novel visible-light-driven Cu₂MoS₄ photocatalyst was prepared by a facile hydrothermal method using Ammonium Tetrathiomolybdate reacting with cuprous chloride in aqua ammonia. The synthetic catalysts were characterized by XRD, UV–vis spectra, XRF and SEM techniques. The influence of the reaction temperature and time on the activities of the catalysts and the morphology of particles was investigated. The results showed that the catalysts exhibited strong absorption in visible light region. It was found that the photocatalyst prepared under hydrothermal condition at 140 °C for about 24 h showed good crystallinity with regular shape, and the highest activity for hydrogen production under visible light irradiation in an aqueous Na₂S–Na₂SO₃ solution. The reason for its better performance has been discussed in detail.     

Synthesis and characterization of nickel oxide/cobalt oxide nanocomposite for effective degradation of methylene blue and their comparative electrochemical study as electrode material for supercapacitor application

In this paper, we have synthesized a nanocomposite of nickel oxide (NiO) and cobalt oxide (Co₃O₄) using l-ascorbic acid which is named A(NC). Herein, A stands for l-ascorbic acid, N stands for nickel oxide (NiO), and C stands for cobalt oxide (Co₃O₄). Where l-ascorbic acid has been used as stabilizing agent/capping agent. Herein, a simple two steps wet-chemical method has been used for the synthesis of the nanocomposite A(NC). This synthesized nanocomposite has been characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), UV–visible spectroscopy, and Fourier transform infrared spectroscopy (FTIR). A comparative electrochemical study has been done using cyclic voltammetry (CV) and galvanostatic charge/discharge (GCD) techniques for supercapacitor performance. This study has been performed with a three-electrode system using 1 M Na₂SO₄ as a supporting electrolyte. Herein, a glassy carbon electrode (GCE) as a working electrode, Ag/AgCl as a reference electrode and Pt electrode as a counter electrode have been used in the electrochemical analysis. The CV curves have been recorded at different scan rates of 5 mV/s, 10 mV/s, 15 mV/s, 20 mV/s, 40 mV/s, 80 mV/s, and 100 mV/s respectively. The value of specific capacitance has been calculated 2.1472 F/g at 5 mV/s and energy density at 0.1074 Wh/kg using the CV curves. Whereas, specific capacitance and energy density have been determined 0.6833 F/g and 0.0342 Wh/kg respectively using the GCD method. Also, the photocatalytic degradation behavior of the synthesized nanocomposite A(NC) has been investigated against methylene blue (MB) dye. Herein, 89.88% MB dye has been degraded with synthesized nanocomposite A(NC) within 360 min in the presence of sunlight.     

Synthesis and high photocatalytic hydrogen production of SrTiO3 nanoparticles from water splitting under UV irradiation

Cubic SrTiO₃ powders were synthesized by three methods: the polymerized complex (PC) method, the solid state reaction, and the milling assistant method. The samples obtained were characterized by X-ray diffraction (XRD), UV–vis spectroscopy (UV–vis), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The mean diameters of the as-synthesized SrTiO₃ particles were 30 nm by the polymerized complex method, 140 nm by the solid state reaction, and 30 nm by the milling assistant method. The photocatalytic activity of hydrogen evolution from water splitting over SrTiO₃ powders by the polymerized complex method is higher than that by the solid state reaction and the milling assistant method. Particle size, uniformity of components, and particle aggregation extent affect the photocatalytic activity of SrTiO₃ for hydrogen evolution. The best rate of photocatalytic hydrogen evolution over SrTiO₃ by the polymerized complex method under UV illumination is as high as 3.2 mmol h⁻¹ g⁻¹.     

Effect of Ni on Pt/C and PtSn/C prepared by the Pechini method

Different compositions of Pt, PtNi, PtSn, and PtSnNi electrocatalysts supported on carbon Vulcan XC-72 were prepared through thermal decomposition of polymeric precursors. The nanoparticles were characterized by morphological and structural analyses (XRD, TEM, and EDX). XRD results revealed a face-centered cubic structure for platinum, and there was evidence that Ni and Sn atoms are incorporated into the Pt structure. The electrochemical investigation was carried out in slightly acidic medium (H₂SO₄ 0.05 mol L⁻¹), in the absence and in the presence of ethanol. Addition of Ni to Pt/C and PtSn/C catalysts significantly shifted the onset of ethanol and CO oxidations toward lower potentials, thus enhancing the catalytic activity, especially in the case of the ternary PtSnNi/C composition. Electrolysis of ethanol solutions at 0.4 V vs. RHE allowed for determination of acetaldehyde and acetic acid as the reaction products, as detected by HPLC analysis. Due to the high concentration of ethanol employed in the electrolysis experiments (1.0 mol L⁻¹), no formation of CO₂ was observed.     

Characterization of hydrogen storage behavior of the as-synthesized p-type NiO/n-type CeO2 nanocomposites by carbohydrates as a capping agent: The influence of morphology

This study proposes a p-type/n-type heterojunction system for electrochemically hydrogen storage. The electrochemical investigation was done as a simple method to evaluate storage capacity. The p-type NiO/n-type CeO₂ mesoporous nanocomposites were prepared via a facile thermal decomposition way that is better than the carbohydrates as a green capping agent. For the first time, the electrochemical hydrogen storage behavior of this nanocomposite was evaluated by chronopotentiometry technique in a potassium hydroxide aqueous solution (6 M KOH) under 1 mA current. The electrochemical measurements display that the hydrogen storage capacity is largely dependent on the design of the nanostructures. Sample No. 2 with the plate-like architecture has higher hydrogen storage capacity than sample No. 1 having particle architecture. The plate-like architecture increases the storage capacity by reducing the diffusion pathway, increasing the surface area, and buffering the volume change during cycling. The hydrogen storage capacity for sample No. 1 and 2 was obtained ≈5500 and 6850 mAh/g, respectively.