Synthesis of Ag3PO4–ZnO nanorod composites with high visible-light photocatalytic activity

Ag₃PO₄ nanoparticles with 50–100 nm in size distributed on the surface of ZnO nanorods with ca. 20 nm in diameter and 1–2 μm in length have been synthesized by a facile method. The Ag₃PO₄–ZnO nanorod composites had much higher photocatalytic activity toward degradation of Rhodamine B (RhB) under visible light irradiation than pure ZnO nanorods, and had better recyclability and stability than pure Ag₃PO₄ nanoparticles. The Ag₃PO₄–ZnO nanorod composite with the molar ratio of Ag₃PO₄:ZnO = 1:40 exhibited the highest photodegradation efficiency of RhB (93%), which was 1.5 times of pure ZnO nanorods.     

Synthesis and characterization of novel PbS–graphene/TiO2 composite with enhanced photocatalytic activity

In this study novel material PbS–graphene/TiO₂ composites were prepared by sol–gel method. The “as-prepared” composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) with an energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), UV–vis diffuse reflectance spectra (DRS) and Raman spectroscopic analysis. The photocatalytic activities were investigated by the degradation of methylene blue (MB) as a standard dye. We observed that coupling of PbS with TiO₂ extends the photoresponse to visible region. This revealed that the excellent photoinduced charge separation abilities and transport properties of graphene make these hybrids as potential candidates for developing high-performance next-generation devices.     

A novel SnS2–MgFe2O4/reduced graphene oxide flower-like photocatalyst: Solvothermal synthesis,characterization and improved visible-light photocatalytic activity

Flower-like SnS₂ decorated with MgFe₂O₄ nanoparticles and reduced graphene oxide (rGO) nanosheets were successfully synthesized by a facile solvothermal method. The morphological and crystal structure results confirmed that MgFe₂O₄ nanospheres were uniformly anchored on the surface of SnS₂ flower-like structure with the decoration of rGO nanosheets. The UV–vis diffuse reflectance spectra indicated that the SnS₂–MgFe₂O₄/rGO photocatalyst had a strong visible light absorption. The sample exhibited the highest photocatalytic activity for the degradation of methylene blue under visible light irradiation. The mechanism of improved photocatalytic activity was finally proposed.     

Carbon nitride nanowires/nanofibers: A novel template-free synthesis from a cyanuric chloride–melamine precursor towards enhanced adsorption and visible-light photocatalytic performance

The development of a graphitic carbon nitride (g-C₃N₄) photocatalyst is of great importance to a variety of visible utilization application fields. The desired high efficiency can be achieved by employing well-controlled g-C₃N₄ nanostructures. In this study, we successfully synthesized high surface area g-C₃N₄ nanowires and nanofibers using a cyanuric chloride and melamine precursor dispersed in a solvothermal reaction and with a subsequent calcination step. The obtained novel nanowire product had a diameter of 10–20 nm and a length of several hundreds of nanometers, while the nanofibers revealed fibrous nanostructures of randomly dispersed fibers with an average diameter of ~15 nm. The adsorption and photocatalytic experimental results indicated that the as-prepared nanowires and nanofibers showed enhanced activities compared with bulk g-C₃N₄. Based on our experimental results, a possible photocatalytic mechanism with hydroxyl and superoxide radical species as the main active species in photocatalysis was proposed. Moreover, our strategy may provide progress toward the design and practical application of 1D g-C₃N₄ nanostructures in the adsorption and photocatalytic degradation of pollutants.     

A novel 2D graphene oxide modified α-AgVO3 nanorods: Design,fabrication, and enhanced visible-light photocatalytic performance

Silver vanadates are promising visible-light-responded photocatalysts with suitable bandgap for solar absorption.However,the easy recombination of photogenerated carriers limits their performance.To overcome this obstacle,a novel 2D graphene oxide(GO)modifiedα-AgVO₃ nanorods(GO/α-AgVO₃ )photocatalyst was designed herein to improve the separation of photocarriers.The GO/α-AgVO₃ was fabricated through a facile in-situ coprecipitation method at room temperature.It was found that the as-prepared 0.5 wt%GO/α-AgVO₃ exhibited the most excellent performance for rhodamine B(RhB)decomposition,with an apparent reaction rate constant 18 times higher than that of pureα-AgVO₃ under visible-light irradiation.In light of the first-principles calculations and the hetero junction analysis,the mechanism underpinned the enhanced photocatalytic performance was proposed.The enhanced photocatalytic performance was ascribed to the appropriate bandgap ofα-AgVO₃ nanorods for visible-light response and efficient separation of photocarriers through GO nanosheets.This work demonstrates the feasibility of overcoming the easy recombination of photogenerated carriers and provides a valuable GO/α-AgVO₃ photocatalyst for pollutant degradation.     

A novel Z-scheme Er3+:Yb0.5Y2.5Al5N0.01F0.01O11.98/g-C3N4–Pt–BiPO4 photocatalyst for enhanced photocatalytic degradation of azofuchsin and ciprofloxacin

In this paper, a novel Z-scheme photocatalyst Er³⁺:Yb_0.5Y_2.5Al₅N_0.01F_0.01O_11.98/g-C₃N₄–Pt–BiPO₄ was synthesized by sol-hydrothermal and calcination methods. The prepared samples were characterized by XRD, SEM, TEM, EDS mappings, XPS, PL, and DRS. In addition, the optimal hydrothermal conditions for the preparation of BiPO₄ were explored with the azofuchsin solution and ciprofloxacin(CIP) solutions as the target pollutants. At the same time, the best calcination temperature and the best calcination time of the Er³⁺:Yb_nY_3−nAl₅N_xF_yO_12−x−y and BiPO₄ were investigated. The results showed that the Z-scheme Er³⁺:Yb_0.5Y_2.5Al₅N_0.01F_0.01O_11.98/g-C₃N₄–Pt–BiPO₄ photocatalyst has strong redox ability, wide absorption range of visible light, and excellent separation effect of electron–hole pairs, which can efficiently degrade organic pollutants and antibiotic.     

WO3/C/Ag3PO4复合材料光催化降解双酚A

以磷酸法制备的活性炭、WO3、AgNO3、Na2HPO4?12H2O为原料,采用共沉淀法制备WO3与C不同含量的系列WO3/C/Ag3PO4复合材料.采用XRD、FTIR、XPS、SEM、TEM和固体紫外漫反射(UV-DRS)技术对其进行了结构表征.在可见光照射下,以双酚A(BPA)模拟污染物,评价WO3/C/Ag3P...     

Synthesis of heterostructured Bi2O3–CeO2–ZnO photocatalyst with enhanced sunlight photocatalytic activity

The development of heterostructured semiconductor photocatalysts makes a noteworthy advancement in environmental purification technology. In this work, a novel heterostructured Bi₂O₃−CeO₂−ZnO, fabricated by a combination of microwave-assisted hydrothermal and thermal decomposition methods, showed an enhanced photocatalytic activity for Rhodamine B (RhB) degradation under sunlight, as compared to pristine ZnO, Bi₂O₃, CeO₂, and commercial Degussa TiO₂-P25. The obtained products were thoroughly characterized by various techniques including X- ray powder diffraction (PXRD), field emission scanning electron microscopy (FE-SEM), elemental color mapping, energy-dispersive X-ray spectroscopy (EDAX), Raman spectrometry, Fourier transform infrared (FT-IR) spectroscopy, UV–visible diffuse reflectance spectroscopy (UV–vis DRS), and photoluminescence (PL) spectroscopy. PXRD analysis reveals that the heterostructure has the monoclinic lattice phase of α-Bi₂O₃, the cubic phase of CeO₂ and the hexagonal wurtzite phase of ZnO. FE-SEM images show that Bi₂O₃−CeO₂−ZnO has an ordered mixture of nanorod and nanochain structures. EDAX, elemental color mapping, Raman and FT-IR analyses confirm the successful formation of the heterostructured Bi₂O₃−CeO₂−ZnO. The UV–Vis DRS results demonstrate that Bi₂O₃−CeO₂−ZnO exhibits wide visible-light photoabsorption in 400–780 nm range. Moreover, the reduction in PL intensity of the heterostructured Bi₂O₃−CeO₂−ZnO, when compared to the pristine Bi₂O₃, CeO₂, and ZnO, indicates enhanced charge separation. The study on the mechanism displayed that the improved photocatalytic activity of Bi₂O₃−CeO₂−ZnO could be attributed to (1) the efficient separation of photoinduced electrons and holes of the photocatalysts, caused by the vectorial transfer of electrons and holes among ZnO, CeO₂ and Bi₂O₃, and (2) the wide visible-light photoabsorption range. This study introduces a new class of promising sunlight-driven photocatalysts.     

WO3/C/Ag3PO4复合材料光催化降解双酚A

以磷酸法制备的活性炭、WO3、AgNO3、Na2HPO4为原料,采用共沉淀法制备WO3/C/Ag3PO4复合材料。采用X 射线衍射（XRD）、傅里叶红外光谱（FT-IR）、光电子能谱（XPS）、扫描电镜（SEM）、透射电镜（TEM）和固体紫外漫反射（UV-DRS）技术对其进行表征。结果表明,Ag3PO4与WO3之间形成异质结。在可见光照射下,以双酚A(BPA)模拟污染物,评价WO3/C/Ag3PO4复合材料的光催化降解性能,并提出 WO3/ C/Ag3PO4 复合材料对BPA的光降解机理。结果表明,在一系列光催化剂中, 23% WO3/ 7% C/ Ag3PO4 复合材料在可见光下对10 mg/L BPA水溶液的降解率在90 min分钟达到95%,明显高于单一的Ag3PO4和WO3。经过3次循环重复,BPA的降解率仍能保持在74%,表明WO3/C/Ag3PO4光催化剂具有良好的稳定性。光催化机理表明,自由基?O- 2和h 在降解过程中起主要作用。     

Facile synthesis and enhanced visible-light photocatalytic activity of Ti3+-doped TiO2 sheets with tunable phase composition? ?

Ti³⁺-doped TiO₂ nanosheets with tunable phase composition (doped TiO₂ (A/R)) were synthesized via a hydrothermal method with high surface area anatase TiO₂ nanosheets TiO₂ (A) as a substrate, structure directing agent, and inhibitor; the activity was evaluated using a probe reaction-photocatalytic CO₂ conversion to methane under visible light irradiation with H₂ as an electron donor and hydrogen source. High-resolution transmission electron microscope (HRTEM), field emission scanning electron microscope, UV-Vis diffuse reflectance spectra, and X-ray diffraction (XRD) etc., were used to characterize the photocatalysts. XRD and HRTEM measurements confirmed the existence of anatase-rutile phase junction, while Ti³⁺ and single-electron-trapped oxygen vacancy in the doped TiO₂ (A/R) photocatalyst were revealed byelectron paramagnetic resonance (EPR) measurements. Effects of hydrothermal synthesis temperature and the amount of added anatase TiO₂ on the photocatalytic activity were elucidated. Significantly enhanced photocatalytic activity of doped TiO₂ (A/R) was observed; under the optimized synthesis conditions, CH₄ generation rate of doped TiO₂ (A/R) was 2.3 times that of Ti³⁺-doped rutile TiO₂.     

Facile ultrasonic-assisted synthesis of micro–nanosheet structure Bi4Ti3O12/g-C3N4 composites with enhanced photocatalytic activity on organic pollutants

The Bi₄Ti₃O₁₂/g-C₃N₄ composites with microsheet and nanosheet structure were prepared through facile ultrasonic-assisted method. The SEM and TEM results suggested that the nanosheets g-C₃N₄ were stacked on the surface of regular Bi₄Ti₃O₁₂ sheets. Comparing with pure Bi₄Ti₃O₁₂ and g-C₃N₄, the Bi₄Ti₃O₁₂/g-C₃N₄ composites showed significant enhancement in photocatalytic efficiency for the degradation of RhB in solution. With the mass ratio of g-C₃N₄ increasing to 10 wt%, the Bi₄Ti₃O₁₂/g-C₃N₄-10% presented the best photocatalytic activity. Its photocatalysis reaction constant was approximately 2 times higher than the single component Bi₄Ti₃O₁₂ or g-C₃N₄. Meanwhile, good stability and durability for the Bi₄Ti₃O₁₂/g-C₃N₄-10% were confirmed by the recycling experiment and FT-IR analysis. The possible mechanism for the improvements was the matched band positions and the effective separation of photo-excited electrons (e^-) and holes (h⁺). Furthermore, based on the results of active species trapping, photo-generated holes (h⁺) and superoxide radical (·O₂^-) could be the main radicals in reaction.     

Ag/Ag2S–TiO2 composite film formed using dual phase Ag/Ag2O layer as a sulfurized layer for enhanced photocatalytic activity

The Ag/Ag₂S–TiO₂ composite films were synthesized through vulcanizing sputtering Ag/Ag₂O dural-phase template capping layer on the TiO₂ film. After hydrothermal vulcanization using thiourea as a sulfur precursor, the initially decorated Ag₂O layer transformed into the Ag₂S. The surface morphology of the continuous block structure of the Ag/Ag₂S composite layer gradually shrinks to form irregular island grains dispersed on the surface of the composite film, with vulcanization reaction duration increased from one to 3 h. The light absorption ability of the Ag/Ag₂S–TiO₂ composite film was enhanced substantially compared to the TiO₂ film because of the surface plasmon resonance effect from the Ag particles and the narrow energy band of the Ag₂S. Among various surface morphologies of the Ag/Ag₂S–TiO₂ composite films, the irregular island Ag/Ag₂S grains-decorated TiO₂ composite film presents superior photoelectrochemical and photocatalytic degradation performances than the composite films consisting of continuous block and spider-web structure of the Ag/Ag₂S decorated layers. The synergistic effects of surface plasmon resonance, Ag pathway between the semiconductors, and Z-scheme charge transfer mechanism explain the high-efficiency photocatalytic activity of the Ag/Ag₂S–TiO₂ composite films.     

Ag/αFe2O3-rGO novel ternary nanocomposites: Synthesis,characterization, and photocatalytic activity

In this research, novel ternary Ag/αFe₂O₃-rGO nanocomposites with various contents of GO were synthesized via a facile one-pot hydrothermal method. Ag/αFe₂O₃-rGO nanocomposites were characterized by X-ray diffraction (XRD), Raman spectroscopy, field emission scanning electron microscopy (FESEM), energy-dispersive X-ray spectrometer (EDX), photoluminescence (PL) spectroscopy, and Fourier transform infrared (FTIR). The results showed that hematite nanoparticles and Ag nanoparticles were well decorated on the graphene surface. Photocatalytic activity of Ag/αFe₂O₃-rGO ternary nanocomposites and pure Ag/αFe₂O₃ was investigated for photodegradation of Congo red dye solution as a model pollutant under UV light irradiation. The ternary nanocomposite with 1.8?mg/ml GO aqueous solution concentration shows higher degradation efficiency under UV light irradiation than the pure Ag/αFe₂O₃ and the nanocomposites with other GO aqueous solution concentrations. It was observed that the adsorption of the dyes on the nanocomposites surface is dependent on the graphene content due to a decrease in the recombination rate, particles size, and increase charge carrier transfer. The results show that the Ag/αFe₂O₃-rGO nanocomposite can be used as an excellent photocatalytic material for degradation of Congo red dye in wastewater. A possible photocatalytic mechanism was proposed for degradation of Congo red dye.     

Enhanced ultraviolet–visible–near infrared driven photocatalytic activity of 1D/0D BiVO4:Er/Yb@Ag/Ag3PO4 Z-scheme heterostructure via a synergetic strategy of plasmonic effect and upconversion luminescence

Expanding the spectral response range to near-infrared (NIR) region and improving carrier separation are the two critical strategies to obtain highly efficient photocatalysts for water pollution control. Herein, a new type of photocatalyst one-dimensional/zero-dimensional (1D/0D) BiVO₄:Er/Yb@Ag/Ag₃PO₄ Z-scheme heterostructure with full spectral response is constructed by an electrospinning coupled with an ethylene glycol assisted hydrothermal method. The optimized BiVO₄:Er/Yb@Ag/Ag₃PO₄ heterostructured nanofibers degrade 69.5% (9 h) and 91.3% (30 min) of tetracycline hydrochloride (TC), 76.7% (9 h) and 99.4% (24 min) of methylene blue (MB) and 38.2% (9 h) and 94.5% (60 min) of bisphenol A (BPA) under NIR light and simulated sunlight excitation, respectively. Under NIR light and simulated sunlight excitation, the MB removal efficiencies of the optimal composite are 9.833 and 1.094 times of Ag₃PO₄ and 20.184 and 11.558 times of BiVO₄, respectively. The superior photocatalytic activity can be attributed to the synergistic effects of the unique 1D/0D contact interface, the porous outer wall of BiVO₄:Er/Yb nanofibers, Ag bridged Z-scheme heterostructure, upconversion (UC) luminescence and the surface plasmon resonance (SPR) effect. This makes BiVO₄:Er/Yb@Ag/Ag₃PO₄ heterostructured nanofibers have the advantages of broadened absorption spectrum, abundant active sites, increased specific surface area, fast electron transfer channels, improved carrier separation efficiency, enhanced photocorrosion resistance and stability. This work provides a new insight in designing and constructing high-performance Ag bridged Z-scheme heterostructure photocatalysts with full spectral response for water pollution control.     

A green and facile one-pot synthesis of Ag–ZnO/RGO nanocomposite with effective photocatalytic activity for removal of organic pollutants

In this study, Ag–ZnO/reduced graphene oxide (Ag–ZnO/RGO) composite was synthesized by a green and facile one-step hydrothermal process. Aqueous suspension containing Ag and ZnO precursors with graphene oxide (GO) sheets was heated at 140 °C for 2 h. The morphology and structure of as-synthesized particles were characterized by field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, and Photoluminescence (PL) spectroscopy which revealed the formation of composite of metal, metal oxide and RGO. It was observed that the presence of Ag precursor and GO sheets in the hydrothermal solution could sufficiently decrease the size of ZnO flowers. The hybrid nanostructure, with unique morphology, obtained from this convenient method (low temperature, less time, and less number of reagents) was found to have good photocatalytic and antibacterial activity. The perfect recovery of catalyst after reaction and its unchanged efficiency for cyclic use showed that it will be an economically and environmentally friendly photocatalyst.     

Synthesis and characterization of α/β-Bi2O3 with enhanced photocatalytic activity for 17α-ethynylestradiol

The α/β-Bi₂O₃ photocatalyst was successfully synthesized by a novel solvothermal-calcination method. The physical and chemical properties of as-prepared samples were characterized based on XRD, XPS, SEM, TEM, EDS, BET, UV–vis DRS and PL techniques. The synthesized α/β-Bi₂O₃ photocatalyst exhibited enhanced photocatalytic activity for 17α-ethinylestradiol (EE2), and 96.9% of EE2 was degraded after only 24 min of visible-light irradiation using α/β-Bi₂O₃ as photocatalyst. The reaction rate constant over α/β-Bi₂O₃ photocatalyst was 1.42, 2.23, 9.22 and 54.1 times higher than pure β-Bi₂O₃, α-Bi₂O₃+β-Bi₂O₃, α-Bi₂O₃ and P25 respectively. Effect of catalyst dosage and pH value was investigated. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation and the experimental results. α/β-Bi₂O₃ was a fairly stable and efficient photocatalyst under the studied experimental conditions, proving that the α/β-Bi₂O₃ photocatalyst was a promising photocatalyst for the practical application.     

A broadband near-infrared Sc1−x(PO3)3:XCr3+ phosphor with enhanced thermal stability and quantum yield by Yb3+ codoping

Broadband near-infrared (NIR) phosphors converted light-emitting diodes (pc-LEDs) have attracted tremendous attention for their great potential in NIR spectroscopy applications. Herein, we report on the photoluminescence (PL) properties of Cr³⁺-doped Sc(PO₃)₃, which exhibits a broadband NIR emission centered at 900 nm with a full width at half-maximum (FWHM) of 161 nm upon excitation at 480 nm. In terms of the examination of spectroscopic parameters, we find that Cr³⁺ ions occupy a weak crystal field site (Dq/B = 1.94) in the Sc(PO₃)₃ host with a stronger electron–phonon coupling (Huang-Rhys factor, S = 5.5), which results in a serious thermal quenching and a low internal quantum efficiency (IQE). Thermal stability and IQE of phosphors can be substantially enhanced by the introduction of Yb³⁺ ions. In the light of the analysis of excited-state dynamics, we demonstrate that the enhancement mechanism is ascribed to the efficient Cr³⁺→Yb³⁺ energy transfer from the thermal sensitive Cr³⁺ centers to the thermal stable Yb³⁺ emitters. An NIR pc-LED device has been finally fabricated by the combination of a blue-emitting chip and a Cr³⁺/Yb³⁺ codoped Sc(PO₃)₃ phosphor whose potential application for broadband NIR pc-LEDs is also discussed.     

Mesoporous CaO–ZrO2 nano-oxides: A novel solid base with high activity and stability

A new solid base, mesoporous CaO–ZrO₂ nano-oxides, was prepared via appropriate sol–gel process. It was found that such solid base showed high basicity and stability. Temperature programmed desorption of CO₂ confirmed that both weak and strong basic sites coexisted on the surface of CaO–ZrO₂ and the basicity could be modified by adjusting Ca/Zr molar ratio of the nano-oxides. The mesoporous CaO–ZrO₂ nano-oxides showed high thermal stability, since X-ray diffraction (XRD) and transmission electron microscopies (TEM) proved that the mesoporous network of this material preserved well even up to 700 °C. At the same time, XRD and Raman spectra indicated that Ca²⁺ incorporated into t-ZrO₂ lattice and the basic sites were firmly anchored to the substrate. As a result, this novel solid base showed remarkable activity and durability in the synthesis of dimethyl carbonate from methanol and propylene carbonate.     

Brazing C/C composites to DD3 alloy with a novel Ag–Cr active braze

A novel Ag–Cr active braze is presented to successfully braze carbon/carbon (C/C) composites to a Ni-based single crystal alloy (DD3). The microstructural characteristics and mechanical properties of C/C–AgCr-DD3 joints are investigated. Results indicate that Cr₂₃C₆ and Ni₂Cr layers can be found nearby C/C and DD3 substrates, respectively. And Cr particles are aggregated outside the Ni₂Cr layer. Amazingly, only Ag matrix and Cr particles can be observed in the brazed seam without the formation of brittle compounds, avoiding damage to the joint plasticity. The thickness of Cr₂₃C₆ and Ni₂Cr layers can be increased with increasing Cr content and brazing temperature. The excessive brazing temperature results in a sharp narrowing of the brazed seam. The nano-indentation test shows that the Cr₂₃C₆ phase exhibits the highest hardness (22.5 GPa) and elastic modulus (316 GPa) among joint phases. The maximum value (27 MPa) of the joint shear strength is obtained using Ag-10 wt% Cr braze at 1040 °C. This work can facilitate revealing effects of the interfacial microstructure on the performance of C/C-metal joints, further promoting their reliable utilization. Furthermore, this study provides a new braze design strategy to avoid the formation of brittle compounds in joints of C/C composites and Ni-based alloy.