Preparation of oriented SiO32− doped TiO2 film and degradation of methylene blue under visible light irradiation

SiO₃^2? doped TiO₂ films with oriented nanoneedle and nanorectangle block structure has been firstly synthesized by hydrothermal synthesis method. The prepared samples are characterized, X-ray diffraction (XRD) results demonstrate that the SiO₃^2? doped TiO₂ films are rutile and brookite phases. The scanning electron microscope (SEM) analysis reveals that the quantity of O₂ affects the morphology of the SiO₃^2? doped TiO₂ films (SiTiA films prepared with unmodified substrate). The SiO₃^2? doped TiO₂ films (SiTiB films prepared with modified substrate) display two layers, one is porous structure, the other is nanoneedle structure. UV–vis, IR, transmission electron microscopy (TEM) and energy-dispersive X-ray (EDX) microscopy all prove that SiO₃^2? have been doped in the TiO₂ crystal structure. They have remarkable red shift and higher photocatalytic activity of degradation of methylene blue than P-25 under visible light (λ > 420 nm) irradiation. Besides, photocatalytic activity of the film is stable during 4 times recycling.     

Photocatalytic decomposition of NO under visible light irradiation on the Cr‐ion‐implanted TiO2 thin film photocatalyst

Transparent TiO₂ thin film photocatalysts were prepared on transparent porous Vycor glass (PVG) by the ionized cluster beam (ICB) method. In order to improve the photocatalytic performance of these thin films under visible light irradiation, transition metal ions such as Cr and V were implanted into the deep bulk inside of the films using an advanced metal‐ion‐implantation technique. The UV‐vis absorption spectra of these metal‐ion‐implanted TiO₂ thin films were found to shift smoothly toward visible light regions, its extent depending on the amount and kinds of metal ions implanted. Using these metal‐ion‐implanted TiO₂ thin films as photocatalysts, the photocatalytic decomposition of NO_x into N₂ and O₂ was successfully carried out under visible light (λ 450 nm) irradiation at 275 K. This revised version was published online in July 2006 with corrections to the Cover Date.     

Photocatalytic behavior of TiO_2 and ZnO prepared with different methods under ultraviolet and visible light irradiation

IntroductionIn recent years photocatalytic oxidation hasreceived considerable attention as an alternativeremediation technology since the method offers anumber of advantages over conventionaltechnologies [1,2] Elimination o…     

Microwave-assisted synthesis of Ag–TiO2/graphene composite for hydrogen production under visible light irradiation

Novel photocatalysts based on silver (Ag), TiO₂, and graphene were successfully synthesized by microwave-assisted hydrothermal method. The prepared photocatalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), Brunauer–Emmett–Teller (BET) specific surface area analysis, X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS). The influence of silver loading and graphene incorporation on photocatalytic hydrogen (H₂) production of as-prepared samples was investigated in methanolic aqueous solution under visible light irradiation (λ≥420 nm). The results showed that Ag–TiO₂/graphene composite had appreciably enhanced photocatalytic H₂ production performance under visible light illumination compared to pure TiO₂, Ag–TiO₂ and TiO₂/graphene samples. The enhanced photocatalytic hydrogen production activity of Ag–TiO₂/graphene composite under visible light irradiation could be attributed to increased visible light absorption, reduced recombination of photogenerated charge carriers and high specific surface area. This novel study provides more insight for the development of novel visible light responsive TiO²⁻ graphene based photocatalysts for energy applications.     

Novel direct Z-scheme AgI/N–TiO2 photocatalyst for removal of polluted tetracycline under visible irradiation

In the study, we doped N into TiO₂ lattice to narrow its band gap energy. Then, the synthesized N doped TiO₂ material was combined with AgI to form AgI/N–TiO₂ (ANT) direct Z scheme materials. The synthesized materials were utilized for photocatalytic removal of tetracycline (TC) using visible irradiation as an excitation source. We also conducted radical scavenging experiments to determine photocatalytic degradation mechanism. We investigated that these photo-excited electrons (e⁻) in N–TiO₂ conduction band tended to combine with the left holes (h⁺) in AgI valence band maintaining h⁺ in the valence band of the N–TiO₂ and e⁻ in the conduction band of the AgI. The remained e⁻ and h⁺ have high redox potential to initiate for photocatalytic decomposition of TC. Thus, the TC degradation by the ANT materials were significant greater than those by single components (AgI or N–TiO₂). We also investigated that the TC degradation by the ANT-30 material, which the AgI: N–TiO₂ molar ratio was 30%, exhibited that highest degradation efficiency. Finally, the ANT photocatalyst exhibited excellent stability during TC degradation processes supporting for its promising potential application in practical systems.     

Effect of different iron precursors on the synthesis and photocatalytic activity of Fe–TiO2 nanotubes under visible light

Fe–TiO₂ nanotubes (Fe-TNTs) were developed to entitled photocatalytic reactions using a visible range of the solar spectrum. This work reports on the effect of different Fe precursors on the synthesis, characterization, kinetic study, material and photocatalytic properties of Fe-TNTs prepared by electrochemical method using three different Fe precursors i.e. (iron nitrate [Fe(NO₃)₃⋅9H₂O], iron sulfate [FeSO₄⋅7H₂O], and potassium iron ferricyanide [K₃Fe(CN)₆]). X-ray diffraction, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, and Fourier transform infrared spectroscopy are used to examine the influence of the Fe precursor on the Fe-TNTs material characterization. Different Fe-TNT properties, such as enhanced photoactivity, good crystallization, and composition of titania structures (anatase and rutile) could be acquired from different iron precursors. Among the three iron precursors, Fe(NO₃)₃ provided with the only anatase phase, yields the highest photocatalytic activity. Congo red is used as a model compound to check the photocatalytic efficiency of synthesized materials because it has a complex aromatic structure which makes it difficult to be biodegraded or oxidized with the aid of chemicals. The photocatalytic efficiency of all Fe-TNT can be arranged in the following order: TNT-FeN > TNT-FeS > TNT-FeK > TNT. The kinetic rate constant of congo red degradation using the Fe-TNT with Fe(NO₃)₃ was 0.44 h⁻¹ with a half-life of 1.57 h⁻¹     

Enhanced performance of g-C3N4/TiO2 photocatalysts for degradation of organic pollutants under visible light☆

Photocatalytic degradation is one of the most promising remediation technologies in terms of advanced oxida-tion processes (AOPs) for water treatment. In this study, novel graphitic carbon nitride/titanium dioxide (g-C3N4/TiO2) composites were synthesized by a facile sonication method. The physicochemical properties of the photocatalyst with different mass ratios of g-C3N4 to TiO2 were investigated by X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM), N2 sorption, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and UV–vis DRS. The photocatalytic performances were evaluated by degradation of methylene blue. It was found that g-C3N4/TiO2 with a mass ratio of 1.5:1 exhib-ited the best degradation performance. Under UV, the degradation rate of g-C3N4/TiO2 was 6.92 and 2.65 times higher than g-C3N4 and TiO2, respectively. While under visible light, the enhancement factors became 9.27 (to g-C3N4) and 7.03 (to TiO2). The improved photocatalytic activity was ascribed to the interfacial charge transfer between g-C3N4 and TiO2. This work suggests that hybridization can produce promising solar materials for envi-ronmental remediation.     

Catalytic activity of mesoporous TiO2−xNx photocatalysts for the decomposition of methyl orange under solar simulated light

Using Tween 80 as pore-directing agent, mesoporous TiO_2?xN_x was prepared via the hydrolysis of TTIP (titanium tetraisopropoxide) in a mixed aqueous solution of isopropanol and acetic acid in the presence of urea. The resulting mesoporous TiO_2?xN_x was characterized by XRD, N₂ adsorption–desorption isotherms, TEM, UV–vis diffuse reflectance spectra and EDS. TEM and N₂ adsorption–desorption isotherms showed that the TiO_2?xN_x has a uniform mesoporous structure. UV–vis spectra revealed that the nitrogen doping caused the absorption edge of TiO_2?xN_x to shift to the visible region. 10%N–TiO₂ exhibited the highest photocatalytic activity for degradation of MO aqueous solution under solar simulated light irradiation.     

A novel noble metal-free ZnS–WS2/CdS composite photocatalyst for H2 evolution under visible light irradiation

A novel ZnS–WS₂/CdS composite photocatalyst for H₂ evolution under visible light irradiation has been successfully synthesized. The loading amounts of WS₂ and ZnS on the CdS surface were optimized. A H₂ evolution rate up to 1224 μmol·h^− 1 has been achieved for the 9.6 mol% ZnS–1 mol% WS₂/CdS photocatalyst. The enhancement of the photocatalytic activity is attributed to the synergistic effect of WS₂ as co-catalyst and ZnS as passivation layer.     

Preparation of cobalt coated TiO2 and WO3–TiO2 nanotube films via photo-assisted deposition with enhanced photocatalytic activity under visible light illumination

Highly ordered TiO₂ and WO₃–TiO₂ nanotubes were prepared by one-step electrochemical anodizing method and cobalt has been successfully deposited on these nanotubes by photo-assisted deposition process. The morphology, crystal structure, elemental composition and light absorption capability of samples were characterized by field emission scanning electron microscope, X-ray diffraction, energy dispersive X-ray spectrometer and ultraviolet–visible spectroscopy methods. All cobalt loaded samples show an appearance of red shift relative to the unloaded samples. The degradation of methylene blue was used as a model reaction to evaluate the photocatalytic activity of these novel visible-light-responsive photocatalysts. Results showed that the photocatalytic activity of bare WO₃–TiO₂ samples is higher than that with undoped TiO₂ sample. Compared with unmodified TiO₂ and WO₃–TiO₂, the Co/TiO₂ and Co/WO₃–TiO₂ samples exhibited enhanced photocatalytic activity in the degradation of methylene blue. Kinetic research showed that the reaction rate constant of Co/WO₃–TiO₂ is approximately 2.26 times higher than the apparent reaction rate constant of bare WO₃–TiO₂. This work provides an insight into designing and synthesizing new TiO₂–WO₃ nanotubes-based hybrid materials for effective visible light-activated photocatalysis. The catalysts prepared in this study exhibit industrially relevant interests due to the low cost and high photocatalytic activity.     

Li–Y doped and codoped TiO2 thin films: Enhancement of photocatalytic activity under visible light irradiation

Sol−gel synthesis based on the self-assembling template method has been applied to synthesize Li–Y doped and co-doped TiO₂ not only to improve simultaneously the structural and electronic properties of TiO₂ nanomaterials but also to achieve Li–Y doping of titania with high photocatalytic reactivity. The characterization of the samples was performed by GXRD, GSDR, FT-IR, and Raman spectroscopy. According to the GXRD patterns, all the observed reflections can be indexed using the anatase form of TiO₂, Which is confirmed by ground state diffuse reflectance and micro-Raman spectra. The Li–Y doped titania materials immobilized as nanostructured thin films on glass substrates exhibit high photocatalytic efficiency for the degradation of toluidine and benzoic acid under visible light irradiation. The development of these visible light-activated nanocatalysts has the potential of providing environmentally benign routes for water treatment.     

Photocatalytic reduction of CO2 to energy products using Cu–TiO2/ZSM-5 and Co–TiO2/ZSM-5 under low energy irradiation

Copper or cobalt incorporated TiO₂ supported ZSM-5 catalysts were prepared by a sol–gel method, and then were characterized by XRD, BET, XPS and UV–vis diffuse reflectance spectroscopy. Ti^3 + was the main titanium specie in TiO₂/ZSM-5 and Cu–TiO₂/ZSM-5, which will be oxide to Ti^4 + after Co was doped. With the deposition of Cu or Co, the efficiency of the CO₂ conversion to CH₃OH was increased under low energy irradiation. The peak production rate of CH₃OH reached 50.05 and 35.12 μmol g^− 1 h^− 1, respectively. High photo energy efficiency (PEE) and quantum yield (φ) were also reached. The mechanism was discussed in our study.     

Ferroelectric photovoltaic and flexo-photovoltaic effects in (1 − x)(Bi0.5Na0.5)TiO3-xBiFeO3 systems under visible light

The anomalous photovoltaic (APV) effect has witnessed great progress from classical ferroelectric photovoltaics to flexo-photovoltaics. Both call for an extension of the spectral response range. Here, we present a comprehensive study on the ferroelectric, photoelectric, and photovoltaic properties of pure (Bi_0.5Na_0.5)TiO₃ (BNT) and 0.3(Bi_0.5Na_0.5)TiO₃–0.7BiFeO₃ (0.3BNT-0.7BFO) ceramics. The data show that pure BNT with typical ferroelectricity exhibits intriguing photovoltaic effect even when illuminated by 550 nm visible light, while the 0.3BNT-0.7BFO solid solution with enhanced visible light absorption shows no ferroelectric photovoltaic due to the negligible ferroelectricity but striking strain-induced flexo-photovoltaic effect. Transmission electron microscopy analysis reveals distinctions in the domain structures and local strain states in pure BNT and 0.3BNT-0.7BFO ceramics, which may account for their differences in photovoltaic behavior. These findings not only deepen the understanding of photovoltaic mechanisms induced by ferroelectric polarization and flexoelectric effect but also highlight a possible candidate for multifunctional photoelectric applications.     

Promoting role of transition metal oxide on ZnTiO3–TiO2 nanocomposites for the photocatalytic activity under solar light irradiation

Transition metal oxide (Fe₂O₃, Co₃O₄ and CuO) loaded ZnTiO₃–TiO₂ nanocomposites were successfully prepared by solid state dispersion method. The structural, morphological and optical properties of samples were characterized by TGA/DTA, XRD, BET, FT-IR, DRS, PL, XPS and SEM techniques. The photocatalytic activity of samples was investigated by degradation of 4-chlorophenol in water under sunlight. The Fe₂O₃ loaded sample was found to exhibit much higher photocatalytic activity than the other composite powders. 7Fe₂O₃/ZnTi sample has the highest percentage of 4-chlorophenol degradation (100%) and highest reaction rate (1.27 mg L⁻¹ min⁻¹) was obtained in 45 min. The enhancement of photocatalytic activity for ZnTiO₃–TiO₂ sample with Fe₂O₃ addition may be attributed to its small particle size, the presence of more surface OH groups, lower band gap energy than other samples in this paper and the presence of more hexagonal ZnTiO₃ phase in the morphology.     

Sol–gel reverse micelle preparation and characterization of N-doped TiO2: Efficient photocatalytic degradation of methylene blue in water under visible light

A series of N-substituted titanium (IV) 2-ethyl-1,3-hexanediolate Ti(C₃₂H₆₈O₈) precursor were synthesized by the sol–gel reverse micelle (SGRM) method. The ethylene diaminetetraacetic acid (Na₂EDTA) has been used as a source of nitrogen n species. The obtained solids were calcined at 500 ?C for 1 h to obtain photoactive phases. The effect of nitrogen content (N/Ti = 0.025; 0.03; 0.05 atomic ratios) is examined. The materials were characterized by XRD, BET, TG/DTA and UV–vis reflectance spectroscopy (DRS). Photocatalytic decolourisation of methylen blue (MB) in aqueous solution was carried out using nano, doped TiO₂. Experimental results revealed that N/Ti = 0.05 atomic ratio N-doped TiO₂ required shorter irradiation time for complete decolourisation of MB than pure nano TiO₂ and commercial (Degussa P-25) TiO₂.     

Inorganic–organic photocatalyst BiPO4/g-C3N4 for efficient removal of gaseous toluene under visible light irradiation

BiPO₄/g-C₃N₄ with different amounts of BiPO₄ was prepared through wet impregnation with calcination method. The BiPO₄/g-C₃N₄ showed large surface area (172.9 m² g^− 1) and the incorporation of BiPO₄ caused a red-shift of g-C₃N₄ in visible light. The photocatalytic degradation of toluene over the samples was investigated. The degradation of toluene could get 82% in BiPO₄/g-C₃N₄ photocatalysts under optimum reaction conditions. The BiPO₄/g-C₃N₄ exhibited a higher photocatalytic activity than pure g-C₃N₄ or BiPO₄. The improved photoactivity of BiPO₄/g-C₃N₄ could be attributed to strong absorption in visible light and effective separation of photo-induced hole-electron pairs between BiPO₄ and g-C₃N₄.     

Preparation and visible light photocatalytic activity of Ag/TiO₂/graphene nanocomposite

Great efforts have been made to develop efficient visible light-activated photocatalysts in recent years. In this work, a new nanocomposite consisting of anatase TiO(2), Ag, and graphene was prepared for use as a visible light-activated photocatalyst, which exhibited significantly increased visible light absorption and improved photocatalytic activity, compared with Ag/TiO(2) and TiO(2)/graphene nanocomposites. The increased absorption in visible light region is originated from the strong interaction between TiO(2) nanoparticles and graphene, as well as the surface plasmon resonance effect of Ag nanoparticles that are mainly adsorbed on the surface of TiO(2) nanoparticles. The highly efficient photocatalytic activity is associated with the strong adsorption ability of graphene for aromatic dye molecules, fast photogenerated charge separation due to the formation of Schottky junction between TiO(2) and Ag nanoparticles and the high electron mobility of graphene sheets, as well as the broad absorption in the visible light region. This work suggests that the combination of the excellent electrical properties of graphene and the surface plasmon resonance effect of noble metallic nanoparticles provides a versatile strategy for the synthesis of novel and efficient visible light-activated photocatalysts.     

Synthesis and enhanced visible light photocatalytic activity of WO3-BiOClxBr1−x heterojunctions with tunable energy band structure

A series of WO₃-BiOCl_xBr_1−x heterojunctions with tunable energy band structure were successfully synthesized via a hydrothermal method. The photocatalytic activities and reaction mechanism of WO₃-BiOCl_xBr_1−x composites were investigated by decomposition of Rhodamine B (RhB). The light absorption ability, energy band structure and photocatalytic activity in WO₃-BiOCl_xBr_1−x heterojunctions could be adjusted by changing the mole ratio of Br and Cl. The results revealed that the WO₃-BiOCl_xBr_1−x composites exhibited the highest photocatalytic activities than pure WO₃ and BiOCl_xBr_1−x under visible light irradiation. The photocatalytic property of WO₃-BiOCl can be strengthened mainly owing to the enhanced light absorption ability, while the photocatalytic activities of WO₃-BiOCl_xBr_1−x (x = 0, 0.25, 0.5 and 0.75) composites could be enhanced by restricting the recombination of photo-generated electrons and holes. Among them, 5% WO₃-BiOCl_0.25Br_0.75 heterojunction shows the highest photocatalytic activity with RhB completely decomposed in 6 min, this can be contributed to the synergetic effects of energy band structure and light absorption ability. Moreover, the holes and superoxide radical anions were considered as the active species during photocatalytic oxidation process, and the possible mechanism of the enhancement of the photocatalytic property was proposed.     

Preparation of nano-Ag-Bi2WO6–TiO2/starch bionanocomposite membranes and mechanism of enhancing visible light degradation of ethylene

Ag–Bi₂WO₆–TiO₂ (ABT) ternary composite photocatalyst was prepared using solvothermal and surface deposition method. Then, the nano photocatalyst was doped into the starch film liquid through internal loading method, and finally, ABT/starch composite film was constructed using tape casting method for visible light catalytic degradation of ethylene. Characterize and analyze the structure and physical properties of nano ABT/starch composite membranes prepared with different ABT loading amounts, and optimize the reaction conditions (ABT addition amount, light intensity, initial concentration of ethylene) on the visible light catalytic degradation performance for ethylene of the composite membrane. The results show that the nano ABT particles and starch molecules have good biocompatibility, and they can be well fused to form a film, without changing the crystal structure of ABT and generating other chemical bond. The results of photocatalytic degradation of ethylene showed that when the loading amount of ABT was 5 wt%, the light intensity was 60.5 mw/cm², and the initial concentration of ethylene was 0.15 mg/L, the ABT/starch film had the best ethylene degradation performance, with a K′ value of 5.6111 × 10⁻⁴ min⁻¹, which is 17.9 times that of the blank starch film. Under the optimal preparation conditions, the thickness, tensile strength, elongation at break of the starch composite film is 168.33 μm, 5.01 Mpa, 32.4%, respectively, and the maximum thermal decomposition temperature is 320.5 °C, which meets the requirements for food packaging materials. After 4 cycles, the catalytic degradation of ethylene by starch composite membrane only decreased by 13.98%, indicating good reusability.