Cerium and carbon-sulfur codoped mesoporous TiO2 nanocomposites for boosting visible light photocatalytic activity

Ce and C-S codoped mesoporous TiO₂ nanocomposites were synthesized via a sol-gel method integrated with an evaporation-induced self-assembly approach.The basic physicochemical characteristics of the synthetic samples were analyzed via a series of characterization techniques.The results reveal that C-S and Ce codoping on mesoporous TiO₂ enhances the photocatalytic activity owing to the synergistic effect caused by narrowing the band gap,enhancing adsorption,trapping and tran...     

Promoting effect and mechanism of neodymium on low-temperature selective catalytic reduction with NH3 over Mn/TiO2 catalysts

Series of Mn/TiO₂ catalysts modified with various contents of Nd for low-temperature SCR were synthesized. It can be found that the appropriate amount of Nd can markedly reduce the take-off temperature of Mn/TiO₂ catalyst to 80 °C and NO_x conversion is stabilized over 90% in the wide temperature range of 100–260 °C. 0.1Nd–Mn/Ti shows higher N₂ selectivity and better SO₂ resistance than Mn/Ti catalyst. The results reveal that Nd-doped Mn/TiO₂ catalyst exhibits larger BET surface area and better dispersion of active component Mn₂O₃. XPS results indicate that the optimal 0.1Nd–Mn/Ti sample possesses higher concentration of Mn⁴⁺ and larger amount of adsorbed oxygen at the surface compared with the unmodified counterpart. In situ DRIFTS show that the surface acidity is evidently increased after adding Nd, especially, the Lewis acid sites, and the intermediate (-NH₂) is more stable. The reaction mechanism over Mn/Ti and 0.1Nd–Mn/Ti catalysts obey the Eley-Rideal (E-R) mechanisms under low temperature reaction conditions. H₂-TPR results show that Nd–Mn/TiO₂ catalyst exhibits better low-temperature redox properties.     

Effect of different doping elements on performance of Ce-Mn/TiO2 catalyst for low temperature denitration

Sm and Ho were doped in Ce-Mn/TiO₂ catalyst respectively to enhance its denitration performance at low temperature.X-ray diffraction(XRD),N₂ adsorption-desorption,X-ray photoelectron spectroscopy(XPS),NH₃-temperature programmed desorption(NH₃-TPD),H₂-temperature programmed reduction(H₂-TPR) and in situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) techniques were used to analyze the structure and performance ...     

Wastewater treatment using Fe-doped perovskite manganites by photocatalytic degradation of methyl orange,crystal violet and indigo carmine dyes in tungsten bulb/sunlight

We documented(ⅰ) the decolorization of wastewater in visible light,which contains methyl orange,crystal violet and indigo carmine dyes,using La_0.7Sr_0.3Mn_1-xFe_xO₃(x=0.0,0.05,0.1 and 0.5) manganites and(ⅱ) efficient separation of photocatalysts from water using magnetic field.These ceramic photocatalysts were sintered at 1050℃ for 12 h.Ceramics were characterized by X-ray diffraction(XRD),soft X-ray absorption spectroscopy(SXAS),Fourier transf...     

Preparation of Ce-TiO2/carbon aerogel electrode and its performance in degradation of 4-chlorophenol

Ce-TiO₂/CA (carbon aerogel) electrode was prepared by sol impregnation approach. The XRD (X-ray diffraction) and Raman spectra reveal that the TiO₂ is anatase. The UV–vis diffuse reflectance spectra show that the optical absorption edge for Ce-TiO₂/CA is red-shifted to 535 nm compared with TiO₂/CA. Under visible light irradiation, the photocurrent density increment on Ce-TiO₂/CA is 75 times that on Ce-TiO₂/FTO (fluorine-doped tin oxide). The electrochemical impedance spectroscopy reveals that the conductivity of Ce-TiO₂/CA is much better than the Ce-TiO₂/FTO. Furthermore, the Ce-TiO₂/CA can be used to the highest electrosorptive photodegradation for 4-chlorophenol wastewater degradation, which is ascribed predominantly to the efficient reduction of electron–hole pair recombination in the photocatalysts.     

Removal of organic pollutants by lanthanide-doped MIL-53(Fe) metal-organic frameworks:Effect of dopant type in magnetite precursor

A series of undoped and lanthanide doped MIL-53(Fe)/Ln-Fe₃O₄(Ln=La,Nd,or Gd) metal-organic frameworks(MOFs) were prepared by the solvothermal method.All prepared samples were characterized by X-ray diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),Brunauer-Emmett-Teller(BET) measurements,scanning electron microscopy(SEM),and thermal analysis.XRD and FT-IR results ascertain the successful MOF formation for all prepared samples.MIL-53(Fe)/La-Fe₃O_...     

Separation and preconcentration of trace indium(III) from environmental samples with nanometer-size titanium dioxide

This work assesses the potential of an adsorptive material, nanometer TiO₂, for the separation and preconcentration of trace indium ions from various aqueous media. The adsorption behavior of nanometer TiO₂ for indium ions was investigated. It was found that the adsorption percentage of the indium ions was more than 96% in pH 3.5–4.0, and the desorption percentage of In(III) ions was more than 99% in pH ≤ 1.5. Good relative standard deviate (1.5%) and lower analytical detection limit (0.45 µg?mL^? 1) were obtained. The adsorption equilibrium was well described by the Langmuir isotherm model with monolayer adsorption capacity of 4566 µg g^? 1 (25 °C). The accuracy of the method is confirmed by analyzing the certified reference material (GBW-07405, GBW07406). The results demonstrated good agreement with the certified values.     

Enhanced photocatalytic degradation of organic dyes from aqueous environment using neodymium-doped mesoporous layered double hydroxide

Neodymium-doped Zn–Al layered double hydroxide (Nd/Zn-Al LDH) with excellent photocatalytic activity was prepared by a one-step hydrothermal method. The morphology and physicochemical properties of as-synthesized photocatalysts were well analyzed by Fourier transform infrared (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), photoluminescence (PL), UV-diffuse reflectance spectroscopy (UV-DRS), and Brunauer-Emmett-Teller (BET) surface analysis. Doping Nd³⁺ into Zn–Al LDH enhances the overall catalytic activity of the nanocomposite, like better electron–hole pair separation, increase in interplanar distance, fast electron transfer, and large surface area. The as-prepared nanocomposite shows excellent degradation of three different dyes under visible light irradiation. The degradation efficiency of these dyes follows the order of Congo red > rose Bengal > fast green. Furthermore, liquid chromatography-mass spectrometry (LC-MS) was employed to propose a possible photocatalytic degradation pathway for Congo Red and Rose Bengal dyes by Nd/Zn–Al LDH. With the help of radical trapping experiments, it is revealed that during the photoexcitation process, the primary reactive intermediates are hydroxyl radicals.     

Preparation of La MnO_3/graphene thin films and their photocatalytic activity

A novel photocatalyst of La MnO3/graphene thin films with the perovskite-type was synthesized by sol-gel process assisted with spin-coating methods on glass substrates.The prepared samples were characterized by scanning electron microscopy(SEM), transmission electron microscopy(TEM), X-ray diffraction(XRD), Brumauer-Emmett-Teller(BET) surface area analyzer, X-ray photoelectron spectroscopy(XPS) and UV-vis diffuse reflectance spectroscopy.Results showed that after the introduction of graphene, the perovskite structure was unchanged and the size of La MnO3 particles was about 22 nm, which uniformed growth in graphene sheet.Determination of contact angle indicated that the contact angle of glass substrate decreased and the hydrophilicity improved after treating with H2SO4 and APTES.The UV-Vis photocatalytic activity of the photocatalysts was evaluated by the degradation of diamine green B.La MnO3/graphene thin films had better photocatalytic ability than La MnO3 and Ti O2 films.The obtained k was 0.5627 and 0.3441 h–1 corresponding to La MnO3/graphene films and Ti O2 films, respectively.     

Effect of rare earth on physical properties of Na0.5Bi0.5TiO3 system: A density functional theory investigation

Na_0.5(Bi_3/4RE_1/4)_0.5TiO₃ (RENBT, RE = Nd, Gd, Dy, and Ho) compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on the spin-polarized density functional theory implemented in the WIEN2k code. Combined charge density distribution and Ti K-edge X-ray absorption spectra reveal that the RENBT compositions with high polarization values are accompanied by a higher TiO₆ distortion, DyNBT, and NdNBT compounds. The effect of the rare-earth elements on the polarization is confirmed experimentally with the collection of the hysteresis loops. The investigation of the electronic properties of the compounds highlights the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements. Besides, the investigation of the chemical ordering shows a short-range chemical ordering for the pure composition and an increased A-site disorder for dysprosium doped NBT system. The increased disorder may speak for increased relaxor properties in the RE doped compositions.     

Evaluating organic acids as alternative leaching reagents for rare earth elements recovery from NdFeB magnets

This study proposes an advanced leaching method using organic acids to recover rare earth elements (REEs) from NdFeB permanent magnets from end-of-life computers hard disk drives (HDDs). The end-of-life HDDs were first dismantled in order to recover NdFeB magnets, which were then thermally demagnetized at 350 °C during 30 min before crushing in a ball mill under inert atmosphere. Scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS) analyses performed on the NdFeB magnets show the heterogeneous structure containing the major matric phase Nd₂Fe₁₄B and the REEs-rich phase containing Nd and Pr oxides. Additionally, X-ray diffraction (XRD) and Mössbauer spectroscopy (MS) analyses on the ground NdFeB magnet show that grinding NdFeB magnets under inert atmosphere helps to minimize its oxidation. Chemical analysis shows that the composition of the ground sample is Nd: 22.8 wt%, Pr: 3.3 wt%, Dy: 1.2 wt%, Fe: 62.6 wt%, Co: 1.5 wt%, B: 0.9 wt%, Ni: 0.6 wt%. Diagrams of speciation and equilibrium phases (E_h vs. pH) were calculated to determine the predominance of the formed species in the REEs–organic acids systems. The influence of the organic acid type (acetic acid, formic acid, citric acid and tartaric acid), the acid concentration (10 vol%, up to saturation), and the solid/liquid (S/L) ratio (0.5%–10%) on NdFeB magnets leaching was investigated employing an optimal experimental design conceived by the statistical software JMP. Acetic acid (CH₃COOH) shows the highest leaching performance of REEs, allowing leaching yields over 90% for Nd, Dy and Pr in the acid concentration range of 1.6–10 mol/L and the S/L ratio range of 0.5%–5% at a temperature of 60 °C. The results presented in this investigation suggest that REEs can be recovered from magnets of end-of-life HDDs using an eco-friendly method assisted by organic acids.     

Influence of manganese rate on structural,optical and electrochemical properties of CeO2 thin films deposited by spray pyrolysis: Supercapacitor applications

The present work aimed to investigate the electrochemical properties of ITO substrates in propylene carbonate (PC) with 0.5 mol/L lithium perchlorate (LiClO₄) medium in the presence of elaborated thin films of cerium dioxide pure and doped with manganese at varying percentages. Ce_1–xMn_xO₂ (x = 0 wt%, 2 wt%, 4 wt% and 6 wt%) were successfully deposited by the spray pyrolysis (SP) technique on the glass substrate and ITO at 450 °C. The effects of manganese (Mn) doped thin films Ce_1–xMn_xO₂ were studied and investigated by using different analyses namely X-ray diffraction (XRD) analysis, Raman spectroscopy method, UV–Vis spectrophotometer technique, atomic force microscopy (AFM) analysis and electrochemical properties. XRD data obtained present a polycrystalline with a face-centred cubic structure of fluorite type. Raman results of undoped and Mn doped thin films show two peaks at 465 and 600 cm^?1, due to the formation of extrinsic oxygen vacancies by the incorporation of Mn into Ce_1–xMn_xO₂ matrix. Energy dispersive spectroscopy (EDS) data show the presence of Ce, O, and Mn elements in the elaborated films. The AFM results reveal that the surface roughness decreases with increasing Mn rate. Further, band gap energy of thin films decreases with increasing in Mn rate due to the formation of defect state between valence and conduction band. The storage capacity of the elaborated Ce_1–xMn_xO₂/ITO/PC + LiClO₄ electrode reaches a maximum of 1.997 mF in the presence of 6 wt% of Mn.     

A comparative study of physicochemical and photocatalytic properties of visible light responsive Fe,Gd and P single and tri-doped TiO2 nanomaterials

High performance Fe-Gd-P tri-doped TiO_2 nanoparticles(1 at% for each dopant) were successfully synthesized by a modified sol-gel method. Various analytical and spectroscopic techniques were carried out to determine the physicochemical properties of the prepared samples, including XRD, EDX, FESEM,BET, FTIR, XPS, PL, EIS and UV-Vis diffuse reflectance spectroscopy. The photocatalytic activities of prepared samples were evaluated by photo degradation of methyl orange(MO) and 4-chlorophenol(4-CP) as model pollutants under visible light irradiation. Effects of each dopant on different properties of TiO_2 nanoparticles were investigated. Results show that Gd and P doping enhances TiO2 surface textural properties by forming Ti-O-Gd and Ti-O-P bonds. It is found that Gd plays a superior role in increasing oxygen vacancies and organic species on TiO_2 surface. Gd doping also facilitates transferring of the photo-induced charge carriers to the surface adsorbed species. The enhanced electronic band structure and visible light response, as well as high electron lifetime of Fe-Gd-P tri-doped sample is mainly attributed to Fe and Gd doping. The tri-doped TiO_2 with rate constant of k_(app)= 1.28 × 10~(-2) min~(-1) for MO and k_(app) = 0.94 × 10~(-2) min~(-1) for 4-CP, shows the highest photodegradation rate among all samples including undoped and single doped samples. The improved photocatalytic performance of Fe-Gd-P tridoped TiO_2 is due to the synergistic effect of enhanced surface chemistry and textural properties,increased number of surface adsorbed hydroxyl groups and organic species, improved visible light absorption, increased lifetime of the photo-induced electron/hole pairs and boosted interfacial charge transfer.     

Corrosion Resistance of Sintered NdFeB Permanent Magnet With Ni-P/Tio22 Composite Film

The Ni-P/TiO₂ composite film on sintered NdFeB permanent magnet was investigated by X-ray diffraction (XRD), environmental scanning electron microscopy (ESEM), and energy dispersive X-ray spectrometer (EDX). The corrosion resistance of Ni-P/TiO₂ film coated on NdFeB magnet, in 0.5 mol/L NaCl solution, was studied by potentiodynamic polarization, salt spray test and electrochemical impedance spectroscopy (EIS) techniques. The self-corrosion current density (i_corr) and the polarization resistance (R_p) of Ni-P/TiO₂ film are 0. 22 μA/cm² (about 14% of that of Ni-P coating), and 120 kΩ • cm² (about 2 times of that of Ni-P coating), respectively. The anti-salt spray time of Ni-P/TiO₂ film is about 2.5 times of that of the Ni-P coating. The results indicate that Ni-P/Ti0₂ film has a better corrosion resistance than Ni-P coating, and the composite film increases the corrosion resistance of NdFeB magnet markedly.     

Photocatalytic reduction of CO2 over Sm-doped TiO2 nanoparticles

Highly efficient photocatalytic reduction of CO₂ is essential for solving the greenhouse effect and energy crisis. In this paper, the Sm-TiO₂ nanocomposites were successfully prepared via sol-gel method. The CO₂ photoreduction activities of synthesized samples were tested under irradiation for 6 h and the results indicate that the 0.5% Sm-TiO₂ catalyst has superior performance and stability. The CO and CH₄ yields of 0.5% Sm-TiO₂ catalyst are 55.47 and 3.82 μmol/g·cat respectively, which are 5.02 and 2.67 times the yield of TiO₂. The possible mechanism of Sm doped TiO₂ was investigated through comprehensive characterization and photoelectrochemical analysis. After the Sm doping, the photo-generated electrons in TiO₂ could migrate to Sm 4f, and some of them can be captured by reducing Sm³⁺ to Sm²⁺, which can lower the recombination rate of electron and hole pairs. Therefore, the enhanced photocatalytic performance could be ascribed to large specific surface area, fast separation rate of electron–hole pairs and high visible light response. This report provides some meaningful attempts in researching the CO₂ photocatalytic reduction.     

Effect of different supports on activity of Mn–Ce binary oxides catalysts for toluene combustion

The effects of support materials on catalytic performance were investigated in catalytic removal of toluene. And the Mn–Ce binary oxides as active components were supported on ZrO₂, SiO₂, γ-Al₂O₃ and TiO₂ support materials. Many techniques, including X-ray diffraction (XRD), Brunauer–Emmett–Teller method (BET), X-ray photoelectron spectroscopy (XPS), temperature-programmed reduction (TPR) and NH₃-temperature-programmed desorption (NH₃-TPD), were used to characterize physicochemical properties. Among the different catalysts, the MnCe/ZrO₂ catalyst with the lowest specific surface area (39.7 m²/g) shows the best catalytic activity. In terms of toluene conversion, the activity order is as follows: MnCe/ZrO₂ > MnCe/TiO₂ ≈ MnCe/SiO₂ > MnCe/Al₂O₃. The better performance of MnCe/ZrO₂ should be attributed to the low-temperature reducibility, and abundant surface species (Mn⁴⁺ and lattice oxygen). And XPS and TPR results reveal that more surface abundant Mn and Ce elements generate good interaction in MnCe/ZrO₂. The weak interaction between metal oxide and support also boosts the dispersion and complete reduction of MnCe oxides at low temperature. In addition, the in-situ DRIFTS results clarify that the carbonate species are main intermediates in MnCe/ZrO₂ sample during surface reaction process.     

Synthesis and characterization of rare earth metal doped tungsten trioxide photocatalyst for degradation of Rhodamine B dye

Nowadays,it is concern for researchers that due to high recombination rate of photogenerated charge carriers in tungsten trioxide(WO₃) nanoparticles,the future applications are limited in the field of photocatalysis.Herein we attempt to synthesize tungsten trioxide nanoparticles with different doping concentrations of lanthanum i.e.2 wt%,4 wt%,6 wt% and 8 wt%.The synthesized samples were characterized by using various characterization techniques:X-ray diffraction(XRD),Raman spectrosco...     

Enhanced visible light photoactivity of TiO2/SnO2 films by tridoping with Y/F/Ag ions

The Y, F, and Ag tridoped TiO₂/SnO₂ composite nanocrystalline film (YFAg–TS) with prominent photocatalytic performance was prepared by the modified sol–gel method and was characterized by utilizing X-ray diffraction (XRD), differential thermal and thermogravimetric (DTA–TG) analysis, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Brunauer–Emmett–Teller (BET) method, ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence (PL). The XRD and DTA–TG results expose that the YFAg–TS catalyst is a mixed phase consisting of anatase, rutile, and chlorargyrite, which is beneficial to improving the photocatalytic performance of TiO₂. The SEM, TEM, and BET results disclose that the YFAg–TS film has smaller nanoparticles, higher specific surface area, and narrower pore size compared with pure TiO₂ film. The XRD and TEM results exhibit that a part of yttrium can enter the TiO₂ lattice to induce lattice distortion. The XPS results confirm the presence of Y³⁺ state in the YFAg–TS sample, and Y³⁺ ions can act as the trapping site of electrons to expedite the separation of electrons and holes. The UV–vis DRS results reveal that the YFAg–TS film has an obvious absorption edge shift and a narrower bandgap (2.70 eV) compared with pure TiO₂ film. The PL results show that the YFAg–TS film has the highest photogenerated electrons and holes separation efficiency and charges transfer efficiency among all samples. The photocatalytic activity of the YFAg–TS was assessed by monitoring the degradation of methyl green and formaldehyde solution. The results manifest that the YFAg–TS film has high stability and excellent photocatalytic performance. The possible synergistic photocatalytic mechanism of YFAg–TS films has been discussed in this paper.     

Preparation of hybrid perovskite-type Li0.33La0.56TiO3 by adding ionic liquids

Perovskite-type Li_0.33La_0.56TiO₃ (LLTO) shows greater advantages than organic liquid electrolytes to be used in all-solid-state lithium-ion batteries with high energy densities. Ionic liquid [BMIM][BF₄] was used to improve the properties of Li_0.33La_0.56TiO₃ by attrition milling in this study. The microstructure, crystallinity and lithium-ion conductivity of the samples were measured by scanning electron microscopy (SEM), X-ray diffraction (XRD), and impedance spectroscopy (IS). The total ionic conductivities of the samples LLTO + x wt% [BMIM][BF₄] increase upon adding [BMIM][BF₄] and the maximum conductivity reaches 4.71 × 10⁻⁴ S/cm when x = 12.5 wt%. The enhancement of the total conductivity is ascribed to the bridging role of the ionic liquid among grains, as evidenced by the low activation energy of 0.17–0.25 eV and the SEM observation. The Li⁺ transference numbers of the hybrid samples are all lower than that of the pure LLTO, indicating the existence of electronic conductions. The hybrid material with a mixed conductivity and good stability in the atmosphere can find uses in all-solid-state lithium-ion batteries to improve the interface contact between electrolytes and electrodes.     

Effect of titanium dioxide and gadolinium dopants on photocatalytic behavior for acriflavine dye

Herein,we report the experimental methodology to optimize the operational parameters of the photocatalytic degradation of acriflavine dye using TiO_2 and Gd~(3+) as dopant.A series of Gd~(3+) doped TiO_2 nanoparticles were synthesized via hydrothermal route and characterized using various techniques like FT-IR,UV,XRD,FESEM and EDS.It is observed that synthesized particles are in the range of 25-30 nm with spherical shape in nature.TiO_2 has rutile phase and the average particle size was estimated from Scherrer's equation.Energy bandgap was estimated using Tauc's plot.The photodegradation was carried out under UV light in pseudofirst order condition.To understand the kinetics,four experimental parameters were chosen as independent variables like percentage of dopant,initial concentration of dye,dosage of catalyst and pH of reaction medium.The degradation efficiency of 92% was observed for 0.5%Gd doped TiO_2 at catalyst dosage of 0.3 g/dm~3,pH 10 and dye concentration of 3×10~(-6) mol/dm~3.It is observed that,the photocatalytic activity of TiO_2 can be increased by using gadolinium as dopant only in optimum concentration.Further,this photocatalyst can be employed to degrade other o rganic pollutants.