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     

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.     

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.     

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.     

Solvothermal synthesis of CNTs–WO3 hybrid nanostructures with high photocatalytic activity under visible light

The CNTs–WO₃ hybrid nanostructures were fabricated by solvothermal synthesis. The morphologies, phase structures and optical properties of the nanostructures were investigated by TEM, XRD, UV–vis DRS and XPS respectively. The CNTs–WO₃ hybrid nanostructures exist higher photocatalytic activity than pure WO₃ nanosheets and the mechanical mixture of WO₃ and CNTs for the degradation of methyl blue (MB) under visible light. This is attributed to their large surface area, absorption enhancement in visible light region and effective separation of electrons and holes. The presence of radical scavengers such as KI, Fe^3 + and methanol in photocatalytic experiments demonstrates that photogenerated electrons are responsible for the photocatalytic degradation of MB on CNTs–WO₃.     

Ultrasonic assisted synthesis of TiO2–reduced graphene oxide nanocomposites with superior photovoltaic and photocatalytic activities

In this work, TiO₂–reduced graphene oxide (RGO) nanocomposites were successfully produced by an ultrasonication-assisted reduction process. The reduction of graphene oxide (GO) and the formation TiO₂ crystals occurred simultaneously. The synthesized nanocomposite was characterized by SEM, EDX, Raman spectroscopy, FTIR, XRD, XPS, UV–vis spectroscopy, photoluminescence spectrometer and electrochemical impedance spectroscopy. As a result of the introduction of RGO, the light absorption of octahedral TiO₂ was markedly improved. The photocatalytic results revealed that weight percent of RGO has substantial influence on degradation of Rhodamine B under visible light irradiation. The enhancement of the photocatalytic activity can be attributed to the enhancement of the visible-light irradiation harvesting and efficiently separation of the photogenerated charge carriers. Meanwhile, upon the RGO loading, the photoelectric conversion efficiency of TiO₂–RGO nanocomposite modified electrode was also highly improved.     

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 effects of plasma-heated TiO2−x particles under visible light irradiation

The photocatalytic characteristics of partially reduced TiO₂ (TiO_2?x ) by plasma treatment and plasma-heated treatment were investigated in the visible-light region. For the visible-light photocatalytic activity of TiO_2?x , plasmaheated treatment shows stronger than plasma treatment significantly. The TiO_2?x by plasma-heated treatment shows broader red-shifted absorption bands than one by plasma treatment in the visible-light region. The surface color of TiO_2?x by plasma treatment and plasma-heated treatment changed from white to sky blue, and to navy, respectively. After exposure to air, the surface color of TiO_2?x changed from sky blue to white for plasma treatment and from navy to beige for plasma-heated treatment.     

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.     

Enhanced the photocatalytic activity of B–C–N–TiO2 under visible light:Synergistic effect of element doping and Z-scheme interface heterojunction constructed with Ag nanoparticles

In order to enhance the photocatalytic activity of TiO₂ under visible light, Ag nanoparticles were introduced into tridoped B–C–N–TiO₂ (TT) catalyst by photoreduction deposition. Ag/B–C–N–TiO₂ (ATT) catalysts with the functions of reducing band gap and carrier recombination were prepared. At the same time, the effect of the amount of Ag on the photocatalytic performance of ATT catalyst was investigated. Through XRD, XPS, PL and other characterization methods, the (211)/(101)/Ag interface heterojunction mechanism similar to the traditional Z-scheme heterojunction was proposed. The intervention of Ag nanoparticles changed the P–N interface heterojunction between (211)/(101) to the (211)/(101)/Ag Z-scheme interface heterojunction. The results show that ATT catalyst exhibits the highest photocatalytic activity when the molar amount of Ag is 0.005% with the MB degradation rate of the ATT catalyst (0.01707 min^?1), which is 14.59 times of TiO₂ (0.00117 min^?1) and 2.02 times of TT (0.00847 min^?1). In addition, the four cycles efficiencies of ATT for MB degradation were all above 94.00%.This study reveals the possibility of construction of Z-scheme heterojunctions between precious metal nanoparticles and different interfaces of TiO₂, and provides a reference for the construction of Z-scheme interface heterojunctions.     

UV-curable polyurethane acrylate–Ag/TiO2 nanocomposites with superior UV light antibacterial activity

Polyurethane acrylate (PUA)–Ag/TiO₂ nanocomposites were synthesized through in situ polymerization. The well-dispersed Ag/TiO₂ nanorods serve as photoinitiator. Meanwhile, the PUA–Ag/TiO₂ nanocomposite films exhibit superior activity toward the photocatalytic degradation of Escherichia coli under UV light. The excellent UV curing and antibacterial activities can be ascribed to the synergistic effect of Ag and TiO₂, which promotes the effective electron/hole separation and thus generates various reactive species. Thin films with these nanoparticles are more hydrophilic after UV illumination. And the antibacterial mechanism of the UV-curable PUA–Ag/TiO₂ nanocomposites was proposed.     

Performance of magnetically recoverable core–shell Fe3O4@Ag3PO4/AgCl for photocatalytic removal of methylene blue under simulated solar light

A novel magnetically recoverable core–shell Fe₃O₄@Ag₃PO₄/AgCl photocatalyst exhibiting rapid magnetic separation, stability and high photocatalytic activity under simulated solar light has been developed. Briefly, Ag₃PO₄ is immobilized on Fe₃O₄ nanoparticles and then an AgCl shell is formed by in situ ion exchange. The complete degradation of the methylene blue (MB) over the Fe₃O₄@Ag₃PO₄/AgCl photocatalyst only took about 60 min, much faster than WO₃–Pd photocatalyst. Fe₃O₄@Ag₃PO₄/AgCl nanocomposites can be easily recovered by a magnet, and reused at least five times without any appreciable reduction in photocatalytic efficiency.     

Antibacterial and photocatalytic active transparent TiO2 crystallized CaO–BaO–B2O3–Al2O3–TiO2–ZnO glass nanocomposites

Transparent TiO₂ crystallized 5CaO–10BaO–65B₂O₃–Al₂O₃–20TiO₂–10ZnO (CBBATZ) glass nanocomposites were fabricated using melt-quenching technique followed by specific heat treatments. As-quenched glass samples were provided three different heat treatments at 630°C for 3, 5, and 10 hours in order to obtain different amounts of TiO₂ nanocrystals in the glass. The presence of rutile phase of TiO₂ nanocrystals in glass was confirmed by X-ray diffraction. The glass nanocomposite heat treated for 10 hours showed a hydrophobic nature with contact angle of 90.90°. Contact angle decreased from 90.90 to 22.20°, when irradiated under ultraviolet (UV) radiation for 45 minutes. This photoinduced hydrophilicity showed a photocatalytic and self-cleaning properties of glass nanocomposite. During photocatalytic ink test, the maximum change in color of Resurin (Rz) ink and 60% degradation in absorbance of ink within 150 minutes under UV radiation were found for glass nanocomposite heat treated at 10 hours. Also, 78% degradation in absorbance of methylene blue dye (pollutant) within 180 minutes under UV irradiation was found for glass naocomposite heat-treated at 10 hours. Antibacterial performance of transparent glass nanocomposite against Escherichia coli was evaluated as well. More than 95% of the bacterial cells were degraded with glass nanocomposite heat-treated at 10 hours. CBBATZ glass nanocomposite found to impart the antibacterial effect through generation of reactive oxygen species (ROS) in aqueous medium. ROS species which was confirmed in the bacterial cell through intracellular ROS generation kit. During evaluation of mechanical properties using nanoindentation technique, the values of hardness and reduced modulus increased by ~26% and 10%, respectively, for glass nanocomposite heat-treated at 10 hours as compared to as-quenched glass.     

Influence of rare-earth oxide additives on the oxidation resistance of Si3N4–SiC nanocomposites

The influence of different rare earth oxide additives (La₂O₃, Nd₂O₃, Sm₂O₃, Y₂O₃, Yb₂O₃ and Lu₂O₃) on the oxidation behaviour of carbon derived Si₃N₄–SiC micro-nanocomposites has been investigated. All investigated composites exhibited predominately parabolic oxidation behaviour indicated diffusion as the rate limiting mechanism. Except the Si₃N₄–SiC composite sintered with Lu₂O₃ the rate-limiting oxidation mechanism for all other materials was an outward diffusion of the additive cations along the grain boundary towards the surface. Such diffusion of cation has been strongly suppressed in the Lu-doped composite because of the beneficial effect of stable grain boundary phase and the presence of the SiC particles predominately located at the grain boundaries of Si₃N₄. Nanoparticles at the grain boundaries act as the obstacles for migration of cations of the additives resulting in superior oxidation resistance of Si₃N₄–SiC–Lu₂O₃ where the rate-limiting step is inward diffusion of oxygen through the oxide layer to the bulk ceramics.     

Enhanced structural,optical, and photocatalytic activity of novel Cd–Zn co-doped Mg0.25 Fe1.75O4 for degradation of RhB dye under visible light irradiation

Cd_xZn_1-xMg_0.25Fe_1.75O₄ (where x = 0.00, 0.25, 0.50, 0.75, 1.00) have been successfully produced by a facile hydrothermal technique for a thorough comparison of structural, optical, and photocatalytic properties (degradation of Rhodamine B -RhB dye under visible light irradiation). X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) confirmed the formation of cubic spinel structure for all of the samples. Fourier transform infrared (FTIR) spectroscopy verified the presence of metal-oxygen (M–O) bonding in the prepared samples with two frequency bands corresponding to phonon vibrational stretching in both the octahedral and tetrahedral lattice positions. UV–Visible Spectrophotometer and photoluminescence (PL) spectroscopy investigated the bandgap variation (2.7 eV-1.7 eV) and emission spectrum peaks appearing in the range of 405–471 nm region. The comparison in the photo-degradation of Rhodamine B (RhB) revealed the superior performance (98% degradation of RhB dye in 80 min having a K value of 0.04966 with excellent reusability) of Cd_0.50Zn_0.50Mg_0.25Fe_1.75O₄ sample having 50/50 dopant ratio of Cd and Zn in the parent Mg Ferrite, attributed to the lowest bandgap, longer lifetime of charge carriers, active octahedral lattice site, electron/hole pair recombination preventions, and the least value of ohmic impedance at higher frequency.     

In-situ generation of metal–metal oxide catalysts for the growth of highly oriented graphitic nanowiggles

In this work we demonstrate an in situ generated growth catalyst that produces highly oriented graphitic nanowiggles (GNWs). GNWs are a new form of disordered nanocarbons with graphite domains stacked perpendicular to the filament axis. They had been prepared by acetylene decomposition at ∼525 °C on Al–Mg mesh coated with iron-based nanoparticles. During CVD, inter-diffusion of Mg, Fe, and O between the electrodeposited Fe particles and the mesh generate flakes which become the active site for nanowiggle growth. The properties of this unique form of carbon were evaluated by TEM, HRTEM, SEM, Raman spectroscopy, XPS and cyclic voltammetry.     

AgBr@Ag/TiO2 core–shell composite with excellent visible light photocatalytic activity and hydrothermal stability

AgBr@Ag/TiO₂ core–shell photocatalysts were fabricated by a facile green route. TiO₂ was uniformly coated on the surface of cubic AgBr, making AgBr@Ag/TiO₂ core–shell photocatalyst show excellent hydrothermal stability. Beneficial from that Ag nanoparticles and AgBr can respond to visible light and core–shell structure can effectively separate the photogenerated electrons and holes, AgBr@Ag/TiO₂ core–shell composites exhibited outstanding visible light photocatalytic activity for the degradation of acid orange 7. The activity of AgBr@Ag/TiO₂ is related to the thickness of TiO₂ shell, and the optimal shell thickness for obtaining the highest activity is 10 nm.     

Metal–organic frameworks-derived TiO2 for photocatalytic degradation of tetracycline hydrochloride

This work will change the common understanding that C doping of MIL-125(Ti)-derived TiO₂ is a key factor in improving its photocatalytic performance, and it can also help to understand the internal relationship between the structure and performance of photocatalytic materials deeply. It provides a simple synthesis method for the wider application of TiO₂ in the field of photocatalysis. Compared with previous studies, this article uses the titanium-based metal-organic framework MIL-125(Ti) to prepare the semiconductor photocatalyst M-TiO₂ by calcination in the air at a lower temperature and shorter time. After analyzing the M-TiO₂ prepared in the experiment, the results can be received that there is no obvious agglomeration and the morphology is almost unchanged, as the frame structure does not collapse at the same time. As a result, the advantages of the large specific surface area and porousness of metal–organic frameworks (MOF) as precursor derivatives are preserved. As for the changes in the micro-morphology, pore structure, and specific surface area of M-TiO₂ compared with the precursor, they are investigated seriatim. The results show that, compared with commercial TiO₂-P25, the performance of M-TiO₂ photocatalytic degradation of tetracycline hydrochloride is 5.7 times that of the precursor metal-organic framework MIL-125(Ti) and 2.2 times that of P25, and has good cycle stability.     

TiO<Subscript>2</Subscript> porous ceramic/Ag–AgCl composite for enhanced photocatalytic degradation of dyes under visible light irradiation

TiO₂ porous ceramic/Ag–AgCl composite was prepared by incorporating AgCl nanoparticles within the bulk of TiO₂ porous ceramic followed by reducing Ag⁺ in the AgCl particles to Ag⁰ species under visible light irradiation. The porous TiO₂ ceramic was physically robust and chemically durable, and the porous structure facilitated the implantation of AgCl NPs. Compared with the bare TiO₂ ceramic, TiO₂ porous ceramic/Ag–AgCl composite exhibited higher photocatalytic performance for the degradation of MO and RhB under visible light irradiation. The reaction rate constants k of MO and RhB degradation over TiO₂ porous ceramic/Ag–AgCl composite was respectively 6.25 times and 3.62 times higher than those recorded over the bare TiO₂ porous ceramic. The photocatalytic activity showed virtually no decline after four times cyclic experiments under visible light irradiation. Scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffraction, UV–Vis diffuse reflectance spectroscopy, photoluminescence spectra and X-ray photoelectron spectroscopy were used to characterize the TiO₂ porous ceramic/Ag–AgCl composite.     

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.