Synthesis and photocatalytic behaviors of Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>–CNT/TiO<Subscript>2</Subscript> composite materials under visible light

Cr₂O₃–CNT/TiO₂ composites derived from chromium acetylacetonate, multi-walled carbon nanotubes (MWCNT) and titanium n-butoxide (TNB) were prepared, and the photocatalytic activity of the Cr₂O₃–CNT and CNT/TiO₂ composites was examined. The Cr₂O₃–CNT/TiO₂ composites were characterized by BET surface area measurement, X-ray diffraction, transmission electron microscopy, and energy dispersive X-ray analysis. The photocatalytic activity was determined from the decomposition of methylene blue (MB) under visible light irradiation. Methylene blue was photodegraded successfully in the presence of the Cr₂O₃–CNT/TiO₂ composite under visible light irradiation.     

Synthesis of AgBr/TiO2/(I/S) composite and its enhanced photocatalytic performance to rhodamine B

Novel AgBr/TiO₂/(I/S) composite was synthesized by deposition–precipitation method. The AgBr/TiO₂/(I/S) composite was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectra, UV–Vis diffuse reflectance spectra and the N₂ adsorption/desorption instrument. Under visible light irradiation, AgBr/TiO₂/(I/S) composite displayed much higher photocatalytic activity than that of pure I/S in the degradation of Rhodamine B (RhB). The RhB dye was degraded by 89% in less than 100 min. All results indicated that AgBr/TiO₂/(I/S) composite have good photocatalytic activity and chemical stability. Moreover, ·O₂^? is demonstrated to be the dominant radical for the photocatalytic degradation of RhB.

     

Fabrication of TiO<Subscript>2</Subscript>/ZnO composite nanofibers with enhanced photocatalytic activity

TiO₂/ZnO composite nanofibers have been successfully prepared by electrospinning technique. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, Raman spectrum, X-ray photoelectron spectroscopy and UV–Vis diffuse reflectance spectroscopy, were used to characterize the as-synthesized nanofibers. The photocatalytic studies revealed that the TiO₂/ZnO nanofibers exhibited enhanced photocatalytic efficiency of photodegradation. Additionally, the recycling experiment of TiO₂/ZnO nanofibers had been done, demonstrating that TiO₂/ZnO nanofibers have high efficiency and stability.     

Multiwalled carbon nanotubes-supported Nickel catalysts for the steam reforming of propane

Multiwalled carbon nanotubes (MWCNTs)-supported nickel catalysts with different metal-loading contents were synthesized trough deposition–precipitation (DP) method for its subsequent performance study on steam reforming reaction of propane. The metal-loading content was set at 5, 10, 20, and 25% of nickel. Results showed that 20 wt% nickel oxide over MWCNTs (20% NiO/MWCNTs) had the best performance, on the propane steam reforming reaction, in terms of H₂ conversion comparing with the rest of the NiO/MWCNTs catalysts (5, 10, 25 wt% Ni) and a nickel over alumina (Ni/Al₂O₃) commercial catalyst. The features of the NiO/MWCNTs catalysts were studied trough FT-IR, Raman spectroscopy, N₂ adsorption–desorption isotherms, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy measurements. The results evidenced that optimum relation between Ni content, Ni dispersion, and particle size played a main role in the catalyst performance, rendering the 20% NiO/MWCNT as the most promising, among the catalysts studied, for the steam reforming of propane.     

Fabrication of TiO2/ZnO composite nanofibers by electrospinning and their photocatalytic property

TiO₂/ZnO composite nanofibers with diameters in the range of 85–200 nm were fabricated via the electrospinning technique using zinc acetate and titanium tetra-isopropoxide as precursors, cellulose acetate as the fiber template, and N,N-dimethylformamide/acetone 1:2 (v/v) mixtures as the co-solvent. After treated with 0.1 mol/L NaOH aqueous solution, TiO₂/zinc acetate/cellulose acetate composite nanofibers were transformed into TiO₂/Zn(OH)₂/cellulose composite nanofibers. TiO₂/ZnO composite nanofibers were obtained by calcinating the hydrolyzed composite fibers at 500 and 700 °C for 5 h. The structure and morphology of composite nanofibers were characterized by scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy. With the blending of ZnO into TiO₂, a new crystallite ZnTiO₃ was formed in addition to the ZnO and TiO₂ crystallites, and the ultraviolet light absorption efficiency was enhanced according to the UV–vis diffuse reflectance spectroscopy. The photocatalytic activity of TiO₂/ZnO composite nanofibers toward the decomposition of Rhodamine B and phenol was investigated. Almost 100% Rhodamine B and 85% phenol were decomposed in the presence of TiO₂/ZnO composite nanofibers under mild conditions. The results demonstrated that the blending of ZnO in the TiO₂/ZnO composite nanofibers increased the photocatalytic efficiency. The optimum ZnO content in the TiO₂/ZnO composite nanofibers was 15.76 wt% to reach the most efficient photocatalytic activity. A schematic diagram of photocatalytic mechanism of TiO₂/ZnO composite nanofibers was also presented.     

Facile fabrication of hierarchical BiVO<Subscript>4</Subscript>/TiO<Subscript>2</Subscript> heterostructures for enhanced photocatalytic activities under visible-light irradiation

BiVO₄/TiO₂ nanocomposites were fabricated by a facile wet-chemical process, followed by the synthesis of TiO₂ hierarchical spheres via hydrothermal method. The BiVO₄/TiO₂ nanocomposites were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV–Vis diffuse reflectance spectroscopy and X-ray photoelectron spectroscopy. The results showed that prepared TiO₂ presented hierarchical spherical morphology self-assembled by nanoparticles and an anatase–brookite mixed crystal phase. The introduction of monoclinic BiVO₄ components retained the hierarchical structures and expanded the light response to around 510 nm. Type II BiVO₄/TiO₂ heterostructured nanocomposites exhibited improved photocatalytic degradation towards methylene blue under visible-light irradiation, especially for the composite photocatalysts with atomic Ti/Bi?=?10, which showed double degradation rate than that of pure BiVO₄. The enhanced photocatalytic mechanism of the heterostructured BiVO₄/TiO₂ nanocomposites was discussed as well.     

Preparation of novel CdS-graphene/TiO2 composites with high photocatalytic activity for methylene blue dye under visible light

In this study, CdS combined graphene/TiO₂ (CdS-graphene/TiO₂) composites were prepared by a sol–gel method to improve on the photocatalytic performance of TiO₂. These composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and transmission electron microscopy (TEM). The photocatalytic activities were examined by the degradation of methylene blue (MB) under visible light irradiation. The photodegradation rate of MB under visible light irradiation reached 90·1% during 150 min. The kinetics of MB degradation were plotted alongside the values calculated from the Langmuir–Hinshelwood equation. 0·1 CGT sample showed the best photocatalytic activity, which was attributed to a cooperative reaction between the increase of photo-absorption effect by graphene and photocatalytic effect by CdS.     

Preparation of metal ion (Fe and Ni) doped TiO2 nanoparticles supported on ZSM-5 zeolite and investigation of its photocatalytic activity

Metal ion doped TiO₂ nanoparticles supported on ZSM-5 zeolite (M-TiO₂/ZSM-5 composites, M = Fe or Ni) were synthesized by hydrothermal method. The prepared composites were characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activities of composites were evaluated by degradation of yellow GX aqueous solution under ambient condition. Fe-TiO₂/ZSM-5 composite showed to be more efficient catalyst for degradation of dye molecules as compared with Ni-TiO₂/ZSM-5 and TiO₂/ZSM-5. Its higher photocatalytic activity is attributed to the effective separation of charge carriers that will be discussed in this paper in detail.     

A facile route to synthesize ternary Cu2O quantum dot/graphene-TiO2 nanocomposites with an improved photocatalytic effect

A Cu₂O quantum dot/graphene-TiO₂ composite, a novel material, was successfully synthesized using a facile hydrothermal method. The hydrothermal reaction was used to load the Cu₂O and TiO₂ particles onto graphene sheets, and the resulting photocatalysts were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, transmission electron microscopy (TEM), Raman spectroscopy, and ultraviolet-visible (UV-vis) diffuse reflectance spectroscopy (DRS). UV spectrophotometry was employed to measure the decrease in the concentration of rhodamine B (RhB), methylene blue trihydrate (MB), and reactive black B (RBB) dyes in an aqueous solution after degradation with the photocatalysts under irradiation with visible light. The results indicate that the quantum dot-sized Cu₂O is a promising material that contributes to the photocatalytic activity of Cu₂O quantum dot/graphene-TiO₂ composites.     

Photocatalytic properties of nanocrystalline TiO2 thin film with Ag additions

In the present study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol–gel spin coating technique. While, by introducing polystyrene (PS) microspheres, porous TiO₂/Ag films were obtained after calcining at a temperature of 500 °C. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry, and scanning electron microscopy to reveal the structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.After 500 °C calcination, the microstructure of PS-TiO₂ film without Ag addition exhibited a sponge-like microstructure while significant sintering effect was noticed with Ag additions and the films exhibited a porous microstructure. Meanwhile, coalescence of nanocrystalline anatase-phase TiO₂ can be observed with respect to the sharpening of XRD diffraction peaks. The photodegradation of porous TiO₂ doped with 1 mol% Ag exhibited the best photocatalytic efficiency where 72% methylene blue can be decomposed after UV exposure for 12 h.     

Nitrogen-doped TiO2 nanotubes with enhanced photocatalytic activity synthesized by a facile wet chemistry method

Nitrogen-doped TiO₂ nanotubes with enhanced photocatalytic activity were synthesized using titanate nanotubes as raw material by a facile wet chemistry method. The resulting nanotubes were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT-IR) spectroscopy, and UV-vis absorption spectroscopy, etc. The photocatalytic activity of nitrogen-doped TiO₂ nanotubes was evaluated by the decomposition of methylene blue under artificial solar light. And it was found that nitrogen-doped TiO₂ nanotubes exhibited much higher photocatalytic activity than undoped titanate nanotubes.     

Synthesis and characterization of Ag/TiO2-B nanosquares with high photocatalytic activity under visible light irradiation

Square-like B doped TiO₂ nanocrystals were first synthesized by a mild solvothermal method with H₃BO₄ and titanium isopropoxide as the precursors, and isopropyl alcohol as reaction medium. Then, Ag nanoparticles were deposited on TiO₂-B nanosquares by photo-deposition. The as-synthesized products have been investigated by photocatalytic reaction test and characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and UV–vis diffuse reflectance spectra (DRS). The results showed that boron was successfully doped into TiO₂ nanosquares under solvothermal condition. The obtained Ag/TiO₂-B composite showed high efficiency in degradation of acid orange II under visible light irradiation. The high photocatalytic performance could be attributed to the synergistic effect of B doping and the plasmon photocatalysis role of the deposited silver nanoparticles over TiO₂.     

Preparation of Fe-doped TiO2 nanotube arrays and their photocatalytic activities under visible light

Fe-doped TiO₂ nanotube arrays have been prepared by the template-based liquid phase deposition method. Their morphologies, structures and optical properties were investigated by scanning electron microscopy, transmission electron microscopy, X-ray diffraction and UV-vis absorption spectroscopy. Their photocatalytic activities were evaluated by the degradation of methylene blue under visible light. The UV-vis absorption spectra of the Fe-doped TiO₂ nanotube arrays showed a red shift and an enhancement of the absorption in the visible region compared to the undoped sample. The Fe-doped TiO₂ nanotube arrays exhibited good photocatalytic activities under visible light irradiation, and the optimum dopant amount was found to be 5.9 at% in our experiments.     

Photocatalytic properties of porous TiO2/Ag thin films

In this study, nanocrystalline TiO₂/Ag composite thin films were prepared by a sol-gel spin-coating technique. By introducing polystyrene (PS) spheres into the precursor solution, porous TiO₂/Ag thin films were prepared after calcination at a temperature of 500 °C for 4 h. Three different sizes (50, 200, and 400 nm) of PS spheres were used to prepare porous TiO₂ films. The as-prepared TiO₂ and TiO₂/Ag thin films were characterized by X-ray diffractometry (XRD) and by scanning electron microscopy to reveal structural and morphological differences. In addition, the photocatalytic properties of these films were investigated by degrading methylene blue under UV irradiation.When PS spheres of different sizes were introduced after calcination, the as-prepared TiO₂ films exhibited different porous structures. XRD results showed that all TiO₂/Ag films exhibited a major anatase phase. The photodegradation of porous TiO₂ thin films prepared with 200 nm PS spheres and doped with 1 mol% Ag exhibited the best photocatalytic efficiency where ∼ 100% methylene blue was decomposed within 8 h under UV exposure.     

Decoration of Cu nanowires with chemically modified TiO2 nanoparticles for their improved photocatalytic performance

In this work, TiO₂ nanoparticles/Cu nanowires (TiO₂NPs@CuNWs) binary composites with tunable coverage of TiO₂ nanoparticles were prepared by a facile method of mixing oleic acid-modified TiO₂ nanoparticles with as-prepared Cu nanowires. Characterization studies including X-ray diffraction spectroscopy, Fourier transform infrared spectroscopy, field emission scanning electron microscopy, and high-resolution transmission electron microscopy were applied to investigate the structure and morphology of the as-synthesized TiO₂NPs@CuNWs binary composites. The photocatalytic activity of TiO₂NPs@CuNWs binary composites was examined by photodegradation of methyl orange. The enhanced photocatalytic efficiency of TiO₂NPs@CuNWs nanocomposites was ascribed to the moderate specific surface area, mesoporous structures, and the electron sink effect of the Cu nanowires. In principle, our investigation indicates that the TiO₂@Cu self-assembled nanostructures can be a promising candidate of composite photocatalysts.     

TiO2 supported on rod-like mesoporous silica SBA-15: Preparation, characterization and photocatalytic behaviour

TiO₂ nanoparticles have been successfully incorporated in the pores of mesoporous silica SBA-15 with different morphologies by a wet impregnation method. The composites were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), inductively coupled plasma (ICP) emission spectroscopy, transmission electron microscopy (TEM), N₂-sorption and UV-Vis diffuse reflectance spectroscopy. The photodegradation of methyl orange (MO) was used to study their photocatalytic property. It is indicated that the morphology of SBA-15 had a great influence on the photocatalytic activity of the composites. When TiO₂/SBA-15 composite was prepared by loading TiO₂ nanoparticles on uniform rod-like SBA-15 of 1 μm length, it showed higher photocatalytic degradation rate than that on less regular but much larger SBA-15 support. This difference was rationalized in terms of the homogeneously distributed and shorter channels of rod-like SBA-15, which favored mass transport and improved the efficient utilization of the pore surface.     

Characterization and enhanced field emission properties of carbon nanotube bundle arrays coated with N-doped nanocrystalline anatase TiO2

Anatase TiO₂ nanocrystals (NCs) were deposited onto patterned carbon nanotube (CNT) bundle arrays to form a TiO₂/CNT composite using metal organic chemical vapor deposition (MOCVD) using titanium-tetraisopropoxide (Ti(OC₃H₇)₄) as a source reagent. The N-doped TiO₂/CNT composite was then fabricated using nitrogen plasma treatment. The structural and spectroscopic properties of TiO₂/CNT composites were characterized by field-emission scanning electron microscopy, micro-Raman spectroscopy and X-ray photoelectron spectroscopy. The combined geometrical structure and low electron affinity effects of N-doped TiO₂ led to a low turn-on field of 1.0 V μm⁻¹ at a current density of 10 μA cm⁻², a low threshold field of 1.9 V μm⁻¹ at a current density of 1 mA cm⁻², a high field enhancement factor of 3.0 × 10³, and long-term stability for the N-doped TiO₂/CNT composite. The results revealed that the N-doped TiO₂/CNT composite can be a potential candidate for field emission devices.     

Synthesis and characterization of TiO2/WO3 composite nanotubes for photocatalytic applications

TiO₂/WO₃ composite nanotubes were synthesized in an anodic aluminum oxide (AAO) template by a sol–gel method. The prepared nanotubes were characterized by transmission electron microscopy, scanning electron microscopy, powder X-ray diffraction, and Brunauer–Emmett–Teller surface area. Using the nanotubes embedded in the AAO templates as catalysts, photocatalytic degradation of methyl orange aqueous solution was carried out under UV light irradiation. The results showed that the TiO₂/WO₃ composite nanotubes with the thickness about 50 nm could be successfully synthesized by this method. TiO₂ showed anatase phase and WO₃ displayed monoclinic phase. The composite nanotubes (TiO₂/WO₃) exhibited higher photocatalytic activity than the pure nanotubes (WO₃ or TiO₂). The possible reason for improving the photocatalytic activity was also discussed.     

Preparation and characterization of ZnO-TiO2 nanocomposite for photocatalytic disinfection of bacteria and detoxification of cyanide under visible light

ZnO-TiO₂ nanocomposite was prepared by modified ammonia-evaporation-induced synthetic method. It was characterized by powder X-ray diffraction, transmission electron microscopy, selected area electron diffraction, and energy dispersive X-ray, UV-visible diffuse reflectance, photoluminescence and electrochemical impedance spectroscopies. Incorporation of ZnO leads to visible light absorption, larger charge transfer resistance and lower capacitance. The nanocomposite effectively catalyzes the inactivation of E. coli under visible light. Further, the prepared nanocomposite displays selective photocatalysis. While its photocatalytic efficiency to detoxify cyanide with visible light is higher than that of TiO₂ P25, its efficiency to degrade methylene blue, sunset yellow and rhodamine B dyes under UV-A light is less than that of TiO₂ P25.     

Facile synthesis of nano-TiO2/stellerite composite with efficient photocatalytic degradation of phenol

In this paper, we report a kind of nano-TiO₂/stellerite composite with enhanced photoactivity, which was synthesized by a typical homogeneous precipitation method followed by a calcination crystallization process using natural stellerite as support. The as-prepared composites were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen adsorption-desorption, high resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The results showed that TiO₂ loading amounts and calcination temperatures had significant influence on the adsorption and photocatalytic degradation properties of phenol. Moreover, it was indicated that the TiO₂ nanoparticles (NPs) with smaller grain size (around 12.0?nm) and narrower size distributions were uniformly deposited on the surface of stellerite as a layer of film. Compared with commercial P25, the received composite exhibited more superior photocatalytic degradation performance towards phenol. The enhanced photocatalytic degradation performance should result from the better dispersibility of TiO₂ NPs and higher separation efficiency of photogenerated electron-hole pairs. This work may set foundation for the practical application of this new composite photocatalyst in the field of wastewater treatment.