High photocatalytic activity over starfish-like La-doped ZnO/SiO_2 photocatalyst for malachite green degradation under visible light

In this work,the unique starlike La-doped ZnO-SiO2 photocatalysts were constructed by an evaporation and calcination method and characterized in detail.UV-vis reflectance and DFT calculation confirm that the doping with La allows to obtain a decrease of band gap of ZnO/SiO_2,which enhances visible light absorbance and oxidizing ability.The photoluminescence intensity reduces greatly,indicating more effective separation of the photo generated carriers of La-doped ZnO-SiO2.Photocatalytic activities of Ladoped ZnO-SiO2 with different doping ratios under simulated visible light irradiation were evaluated with malachite green(MG) as a model pollutant.Under optimized conditions including solution pH of 8,15 mg/L of MG solution and 15 mg of catalyst dosage,0.2% La-ZnO-SiO2 exhibits the best catalytic activity in photodegradations of MG in water.The removal and mineralization efficiency of MG can reach 96.1%and 70.9% in 140 min,respectively.The as-prepared catalysts present superior stability and recyclability after four times reuse.Moreover,selective quenching experiments indicate that hydroxyl radical(·OH),hole(h~+) and superoxide radical(·O_2~-) are the main reactive species responsible for MG degradation.Possible mechanism for photocatalytic elimination of MG over La-doped ZnO/SiO_2 photocatalyst is finally proposed.     

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...     

Fabrication of highly efficient heterostructured Ag-CeO2/g-C3N4 hybrid photocatalyst with enhanced visible-light photocatalytic activity

On the basis of hydrothermal synthesis of Ag-CeO₂ microspheres, Ag-CeO₂/g-C₃N₄ composite photocatalyst with heterostructure was prepared by simple solvent evaporation of Ag-CeO₂ and g-C₃N₄. To characterize the composition, structure, morphology and light absorption properties of the as-prepared Ag-CeO₂/g-C₃N₄ composites, XRD, FTIR XPS, SEM, TEM, PL, BET and UV-vis DRS were used, respectively. The as-prepared photocatalyst was subjected to photocatalytic degradation of pollutants, and the prepared composite material has excellent photocatalytic activity for photodegradation of methylene blue (MB). The research shows that the photocatalytic properties of Ag-CeO₂/g-C₃N₄ composites were related to the mass ratio of Ag-CeO₂ microspheres and g-C₃N₄ nanosheets. When the ratio of Ag-CeO₂ microspheres: g-C₃N₄ is 1:5, the composites have the highest photocatalytic activity, which was 9.6 and 3.3 times that of single Ag-CeO₂ and g-C₃N₄, respectively. The improvement of photocatalytic activity is attributed to the heterostructure between the composite materials and the addition of noble metal silver, and the degradation of methylene blue by the visible light irradiation material is greatly improved. Finally, an attempt was made to analyze the principle of photocatalytic degradation of pollutants in prepared materials.     

Transition metal doping effect and high catalytic activity of CeO2–TiO2 for chlorinated VOCs degradation

A series of transition metals (Fe, Co, Ni, Cu, Cr and Mn)-doped CeO₂–TiO₂ catalysts were prepared by the sol–gel method and applied for the catalytic removal of 1,2-dichloroethane (DCE) as a model for chlorinated VOCs (CVOCs). The various characterization methods including X-ray diffraction (XRD), N₂ adsorption–desorption, UV-Raman, NH₃ temperature-programmed desorption (NH₃-TPD) and H₂ temperature-programmed reduction (H₂-TPR) were utilized to investigate the physicochemical properties of the catalysts. The results show that doping Fe, Co, Ni or Mn can obviously promote the activity of CeO₂–TiO₂ mixed oxides for DCE degradation, which is related to their improved texture properties, acid sites (especially for strong acidity) and low-temperature reducibility. Particularly, CeTi–Fe doped with moderate Fe exhibits excellent activity for 1,2-dichloroethane (DCE) degradation, giving a T_90% value as low as 250 °C. More importantly, only trace chlorinated byproducts were produced during the low-temperature degradation of various CVOCs (dichloromethane (DCM), trichloroethylene (TCE) and chlorobenzene (CB)) over CeTi–Fe1/9 catalyst with high durability.     

A novel Ga(Ⅲ)coordination complex as an efficient sensitizer for enhancing photocatalytic activity of TiO2/rGO nanocomposite

Narrow solar-light response range and rapid charges recombination are the main technical barriers in TiO₂ photocatalysis technology.To overcome these restrictions,in this work we synthesized a novel binuclear gadolinium(Ⅲ) coordination complex,[Gd₂(DPDB)₆(DMF)₆(H₂O2)](DPDB=[(4-dimethylamino)phenyldiazenyl] benzenesulfonate),which was used as an inorganic sensitizer for boosting the visible light-harvesting and quantum efficiency o...     

Synthesis of yttrium and cerium doped ZnO nanoparticles as highly inexpensive and stable photocatalysts for hydrogen evolution

Yttrium and cerium co-doped ZnO nanoparticles were synthesized by combustion route and characterized using X-ray diffraction(XRD),scanning electron microscopy(SEM),Brunauer-Emmett-Teller(BET),energy dispersive spectroscopy(EDS),X-ray photoelectron spectroscopy(XPS),UV-visible diffuse reflectance spectroscopy(UV-vis DRS),photoluminescence(PL)and electrochemical impedance spectroscopy(EIS)techniques.The introduction of yttrium ions has efficiently increased the relative percentage of Ce³⁺ions in ZnO.Yttrium and cerium co-doped ZnO shows efficient photo activity for hydrogen evolution(10.61 mmol/((g·h))higher than previously reported optimal value for rare earth codoped ZnO photocatalysts.This remarkably increased hydrogen evolution can be ascribed to the synergy between electronic anchoring effect of Y³⁺/Y²⁺and Ce⁴⁺/Ce³⁺redox couples.This report presents new idea for the synthesis of efficient photocatalyst using economical route and ion anchoring effect.The hydrogen evolution was also tested using Na₂S and Na₂SO₃as electron donors under visible light illumination.The synthesized photocatalysts also exhibit high stability.     

LaO_x(OH)_y supported platinum catalysts for CO oxidation:Deactivation by formation of lanthanum carbonate

Platinum catalyst for CO oxidation has been studied for decades,due to its high activity and good stability.In this work,we prepared three different lantha num oxide or hydroxide supports(LaO_x(OH)_y),and deposited platinum(Pt) with 0.5 at% via an impregnation approach to synthesize Pt/LaO_x(OH)_y catalysts.However,we find that these catalysts perform a poor stability for the CO oxidation reaction.The fresh and used samples were comprehensively characterized by multiple techniques including power X-ray diffraction(XRD),X-ray absorption fine structure(XAFS),transmission electron microscopy(TEM),temperature-programmed reduction by carbon monoxide(CO-TPR) and thermogravimetric analysis(TGA),to demonstrate that the oxidized platinum atoms or clusters,without any component of Pt-Pt metallic bond,are highly dispersed on the surface of LaO_x(OH)_y.Furthermore,the as-formed lanthanum carbonate(La₂O₂CO₃) during the exposure to ambient circumstances or in the reaction atmosphere of CO+O₂,severely impair the reactivity of Pt/LaO_x(OH)_y.On the basis of the obtained experimental results,we have drawn a conclusion that the oxidized P_tO_x atoms or PtxOy clusters are the active species for CO oxidation,while the formation of lanthanum carbonate is the origin of deactivation on reactivity.     

Fabrication of La_(1-x)Ca_xFeO_3 perovskite-type oxides with macro-mesoporous structure via a dual-template method for highly efficient soot combustion

A series of three-dimensionally ordered macro-mesoporous(3DOMM) La_(1-x)Ca_xFeO_3(x=0-0.3)perovskite-type oxides were designed and successfully fabricated for the first time via a dual-template method.In which,PMMA and Brij-56 were employed as the hard template and soft template,respectively.It is found that 3 DOMM La_(1-x)Ca_xFeO_3 exhibits abundant wormlike mesoporous channels about 3 nm in diameter on macroporous skeleton walls.The excellent catalytic activity of soot combustion benefits from not only the well-designed hierarchical porous structure of catalyst,but also the redox electron pair of Fe~(3+)/Fe~(4+) induced by the doping of low-valent alkaline earth metal Ca to A-site of LaFeO_3.3DOMM La_(0.8)Ca_(0.2)FeO_3 exhibits superior catalytic performance for soot combustion,which shows T_(50) of396℃.It is 189℃lower than that without catalyst.A combination of structure and composition in the design of catalyst can be widely extended to other catalytic systems.     

RE-NiOx (RE=Ce,Y, La) composite oxides coupled plasma catalysis for benzene oxidation and by-product ozone removal

Plasma-coupled catalysis is a promising volatile organic co mpounds(VOCs) removal technology because of its interactional principles of plasma decomposition and catalytic oxidation.However,the problem of harmful by-products is still in trouble.A series of rare earth doped RE-NiO_x(RE=Ce,Y,La) composite oxides were synthesized by metal organic frameworks(MOFs)-derived method for coupled plasma oxidation of benzene and by-product ozone removal.Compared with plasma alone,the 1%La-NiO_...     

A comparative study of hydrothermal aging effect on cerium and lanthanum doped Cu/SSZ-13 catalysts for NH_3-SCR

Ce-or La-doped Cu/SSZ-13 catalysts were prepared by a hydrothermal method and Cu,Ce or La ions were incorporated through stepwise ion exchange,The catalyst activity was measured for the ammonia selective catalytic reduction reaction.The structure and composition of catalyst were characterized by using X-ray diffraction,scanning electron microscopy,inductively coupled plasma mass spectrometry solid-state NMR,NH_3-TPD techniques,and the active components were examined by XPS and XANES.The results indicate that the Ce and La doping can both completely preserve the SCR activity of Cu/SSZ-13 above 300℃,but there is also a decrease of activity below 200℃.On the other hand,Ce doping is beneficial to the formation of framework aluminum,stabilizes molecular sieve framework and Cu active sites of Cu/SSZ-13,thereby improves the catalyst hydrothermal stability.But La doping will decrease the amount of framework aluminum and Cu active sites of Cu/SSZ-13 after hydrothermally aging,even destroy zeolite CHA structure.This is quite harmful to the catalyst hydrothermal stability.     

A novel extractant bis(2-ethylhexyl) ((2-ethylhexylamino)methyl) phosphine oxide for cerium(IV) extraction and separation from sulfate medium

By introducing the amine group into phosphorus extractant, a novel aminophosphine compound bis(2-ethylhexyl) ((2-ethylhexylamino)methyl) phosphine oxide (DEHAPO, abbreviated as A) was synthesized for the extraction of cerium (IV) (Ce(IV)) from sulfate medium (H₂SO₄). The influence factors including extractant concentration, H₂SO₄ concentration and temperature on the Ce(IV) extraction were investigated and discussed. It is found that the extraction ability of Ce(IV), thorium (IV) (Th(IV)) and rare earths (REs(III)) (La, Gd, Yb) decreases in sulphate medium in the following order: Ce(IV) > Th(IV) > REs(III). The extraction process is an exothermic reaction and the thermodynamic parameters were calculated. The extracted complex of Ce(HSO₄)₂SO₄·A in loaded organic solution was identified by the slope methods and further proved by FT-IR spectral analysis. Stripping studies indicate that Ce(IV) can be effectively stripped from the organic phase. The results of separation factors (β) and saturation loading capacity demonstrate that DEHAPO could be used to selectively extract Ce(IV) from sulphate medium with high separation efficiency and good extraction ability.     

Preparation and application of iron oxide/persimmon tannin/ graphene oxide nanocomposites for efficient adsorption of erbium from aqueous solution

Rare earth elements (REEs) are used for the development of new energy materials owing to their intrinsic physicochemical property. However, excess REEs in water threaten the safety of animals, plants and humans. An efficient way to separate REEs from the water is therefore needed. In this study, a biosorbent consisting of iron oxide (Fe₃O₄), persimmon tannin (PT), and graphene oxide (GO) as Fe₃O₄/PT/GO was prepared, and the adsorption of trivalent erbium (Er³⁺) ions from aqueous solution was investigated. The adsorption process for Er³⁺ ions conforms to pseudo-second order kinetic and the Langmuir isotherm model behavior. Thermodynamic studies indicate that the adsorption process is spontaneous and endothermic. Scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), thermogravimetric analysis (TGA), Fourier-transform infrared (FT-IR) spectroscopy, Brunauer-Emmett-Teller (BET) analysis, and vibrating sample magnetometer (VSM) were used to assess the adsorption mechanism of Er³⁺ ions onto the Fe₃O₄/PT/GO biosorbent. A combination of electrostatic interactions, redox reactivity and chelation are responsible for adsorption of Er³⁺ ions on the Fe₃O₄/PT/GO biosorbent. The magnetic Fe₃O₄/PT/GO biosorbent can be easily separated under the magnetic field for effective recycle of Er³⁺ ions from aqueous solution. Therefore, this new biomass composite holds great promise for wastewater treatment.     

Application of MnCeOx supported on palygorskite and Al(OH)3 for HCHO oxidation: Catalytic performance and stability

Indoor formaldehyde (HCHO) is an important air pollutant, while it is very difficult to reduce HCHO to low-level (e.g. <0.08 mg/m³). Catalytic oxidation at ambient temperature has been increasingly recognized as one of the important methods to mitigate HCHO pollution due to its good effectiveness, stability, and recyclability. To further improve the activity of catalytic oxidation, this study develops the integrated MnCeO_x catalysts supported on palygorskite (Pal) and aluminium hydroxide (Al(OH)₃). Our results indicate that the synergistic interaction in MnCeO_x through the oxygen transfer mechanism from the oxygen reservoir CeO₂ to MnO_x significantly improves the activity. Pal, Al(OH)₃, etc. were applied as the supports with a focus on their dispersion, microstructure, strength, and relative role. MnCeO_x can be anchored on the surface of Al(OH)₃ with high dispersion. With the integrated catalyst, HCHO concentration decreases from 1.012 to 0.086 mg/m³ within 48 h. Higher oxidation activity of MnCeO_x powder may be ascribed to the amount of active components on the surface. The incorporation of ZSM–5 and activated carbon can improve the adsorption of HCHO, and all integrated catalysts exhibit stronger activities, with HCHO being degraded to the level lower than 0.08 mg/m³. Meantime, the samples exhibit good stability and strength (20.2 MPa) without obvious decrease over five consecutive stability experiments.     

A New Ternary Fluorescent Europium Complex with Bis(Diphenyl Phosphine Oxide) Methane and Thenoyltrifluoroacetone

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A potential red-emitting phosphor Ca_2YTaO_6:Eu~(3+):Luminescence properties,thermal stability and applications for white LEDs

A novel red-emitting phosphor tantalate Ca_2 YTaO_6:Eu~(3+)was synthesized by a solid-state reaction.The purity and surface morphology of the phosphors were characterized.The Ca_2 YTaO_6:Eu~(3+)phosphors show a sharp emission peak at 612 nm under near-ultraviolet(n-UV) at 395 nm because of the ~5 D_0→~7 F_2 transition of Eu3+.The optimal Eu3+doping concentration in Ca2 YTaO_6 is 40 mol% and the critical energy-transfer distance of Eu3+ions was calculated to be 0.9 nm.The emission spectra of Ca_2 YTaO_6:Eu3+from 300 to 480 K were investigated.The thermal-quenching temperature(T_(0.5)) of Ca_2 YTaO_6:Eu~(3+)is above 480 K.The color purity of Ca_2 YTaO_6:40 mol%Eu3+is as high as 99.8%.The luminescence lifetime of Ca_2 YTaO_6:40 mol%Eu~(3+)was also discussed.The high color purity and high thermal stability of Eu~(3+)-doped Ca2 YTaO6 phosphors contribute to its application value in white lightemitting diodes(w-LEDs).     

A strategy for improving sinterability and electrical properties of gadolinium-doped ceria electrolyte using calcium oxide additive

In this study,Gd and Ca co-doped ceria electrolytes with the compositions of Ce_(0.8)Gd_(0.2-x)Ca_xO_(2-δ)(x=0-0.08) were prepared by a novel gel-casting method.The effects of the addition of Ca on the phase compositions,sintering behavio r,and electrical prope rties of samples were investigated.According to the scanning electron microscope results and relative density measurement results,it is found that the addition of particular quantity of CaO can promote the sintering densification with a uniform grain growth.When the sintering temperature is 1400℃,the sample with 6 mol% addition of Ca has the highest relative density,which reaches 98.5% of the theoretical density.The electrical properties testing results confirm that the electrical conductivity of the samples can be improved significantly by doping appropriate CaO content.The maximum conductivity of 0.082 S/cm can be obtained at 800℃ in the Ce_(0.8)Gd_(0.12)-Ca_(0.06)O_(1.87) sample.It suggests that CaO can be used as an effective sintering aid and a codopant on the optimization of electrical properties for ceria-based electrolytes.     

Ce~(3+) doped BaLu_2Al_2Ga_2SiO_(12)——A novel blue-light excitable cyan-emitting phosphor with ultra-high quantum efficiency and excellent stability for full-spectrum white LEDs

It is well known that cyan-emitting phosphors play a very important role in full-spectrum white LEDs.A large number of cyan-emitting phosphors have been reported in the past few years,however,most of them can only be effectively excited by near-ultraviolet light.There are very few cyan-emitting phosphors that can be intensively excited by blue light(440 and 470 nm).Here,a novel blue-light excitable cyan-emitting phosphor BaLu_(1.95)Ce_(0.05)Al_2Ga_2SiO_(12) with excellent performance is reported.The cyan phosphor has a cubic structure in space group ■ with a=1.205379(3) nm,which can be easily obtained through a solid-state reaction pathway.The emission peak of the cyan phosphor is located at 500 nm and its internal quantum efficiency is as high as 90.01% when excited at 455 nm at 25℃.The cyan phosphor exhibits superior resistance against thermal quenching of luminescence,and its intensity at 125℃ is as strong as 92.14% of the intensity at room temperature.Meanwhile,it also shows an outstanding resistance against water,where its luminescence intensity is hardly changed after being immersed in pure water for 528 h.The white LED lamp prepared by employing the obtained BaLu_(1.95)-Ce_(0.05)Al_2Ga_2SiO_(12) as cyan phosphor displays remarkable optical properties with CCT=4441 K,R_a=93.7,CRI=90.4 and CIE 1931(x,y) as(x=0.3648,y=0.3752).The experimental results demonstrate that BaLu_(1.95)Ce_(0.05)Al_2Ga_2SiO_(12) is a promising cyan-emitting phosphor with great application potential in full-spectrum white LEDs.     

A novel fluorescent sensor for Al~(3+) and Zn~(2+) based on a new europium complex with a 1,10-phenanthroline ligand

A new europium complex Eu(tta)₃Li(la)based on 1,10-phenanthroline derivative(Li=(2-(3,5-dimethoxyphenyl)-1 H-imidazo[4,5-f][1,10]phenanthroline),tta=2-thenoyItrifluoroacetone)was designed and synthesized.Its structure was characterized by¹H and¹³C NMR,elemental analysis,UV-vis,fluorescence spectra and single crystal X-ray diffraction.The crystal of the complex la belongs to monoclinic system with the space group P2_1/n.The europium complex la in the solid and in the solution displays the typical emission of Eu(III)ion centered at 612 nm as a result of the electric dipole transition(⁵D₀-?⁷F₂).It exhibits high quantum yield(20.42%),long lifetime(0.29 ms)and good CIE color coordinate(0.67,0.33)in solid.In addition,the complex shows high sensitivity and selectivity towards Al³⁺and Zn²⁺in methanol solution which can be attributed to the Al³⁺/Zn²⁺cation instead of Eu³⁺in the complex la.The LODs for Al³⁺and Zn²⁺were calculated to be 5.880×10^-7and 7.678×10^-8mol/L,respectively.Besides,the additions of Al³⁺and Zn²⁺express remarkable color changes from red to bright blue and ivory that can be clearly observed by the naked eye respectively.     

A preliminary study of polymer inclusion membrane for lutetium(III) separation and membrane regeneration

This paper reports on the selective transport of Lu(III) from La(III) and Sm(III) through a polymer inclusion membrane (PIM) composed of 40 wt% di(2-ethylhexyl) phosphinic acid (P227) and 60 wt% poly(vinylidene fluoride) (PVDF). Basically, the changes in surface morphology, thickness and water contact angle of this PVDF-based PIM containing P227 (P227@PVDF PIM) with different polymer concentrations were investigated. By solvent extraction experiments, it is found that Lu(III) can be selectively extracted from La(III) and Sm(III) at pH 1.5 in hydrochloric acid solution. According to this result, P227@PVDF PIM was used to selectively transport Lu(III) from hydrochloric acid feed solution containing similar concentration of La(III) and Sm(III). The recovery factor of Lu(III) is 91% after 36 h, and about 5% of Sm(III) was also transported through the PIM. The concentration of La(III) in the feed solution and the stripping solution does not change. Furthermore, to overcome the ubiquitous decline of transport efficiency caused by the loss of carrier or the damage of membrane structure after long-term use of PIMs, a process for regenerating PIMs was first proposed and implemented. By comparison of the regenerated PIM with the normal PIM, there is almost no difference in the SEM image, ATR-FTIR spectrum and Lu(III) transport efficiency. It is expected that P227@PVDF PIMs have the potential to be applied to the grouped separation of rare earth elements (REEs), and this study also can be as an inspiration for the further study on the PIMs regeneration process.     

Synthesis of photocatalytic La(1-x)AxTiO3.5-δ(A=Ba,Sr, Ca) nano perovskites and their application for photocatalytic oxidation of congo red dye in aqueous solution

A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites were prepared by sol-gel method and characterized using thermogravimetry/differential thermal analysis(TGA/DTA), X-ray diffraction(XRD), ultraviolet-visible(UV-Vis) spectroscopy and transmission electron microscopy(TEM). XRD analysis showed that the La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites derived after calcination at 800 oC were in single phase with orthorhombic structure. The particle size of all nano perovskites was found to be ~20 nm. The synthesized nano perovskites were tested for the photocatalytic decomposition of an azo dye, Congo red. The sequential behavior of La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nanoperovskites for photocatalytic decomposition of congo red in aqueous solution by visible light at room temperature was studied at various time intervals and the efficiency of degradation of the nanoperovskites was compared. Among all the A-site substituted La0.8A0.2TiO3.5–δ(A=Ba, Sr, Ca) nano perovskites, Ba substituted compound showed the highest dye degradation.