Fabrication and Photocatalysis of TiO2 Flower-like Nanostructures

TiO2 nanostructures were fabricated by a reaction of Ti foils in H2O2 solution at mild temperature, Porous TiO2 nanostructurcs, well adhered to Ti foil surfaces, were formed at 80 ℃ in 10 rain, and then flower- like and rod nanostructures formed in succession after a longer reaction time. Samples prepared at 80 ℃ for 4 h arc amorphous, and anatase-dominated crystal phase emerged in the sample prepared for as long as 10 h. Almost pure anatase phase were obtained in TiO2 nanostructures by annealing the samples at a temperature of 300 ℃. Photoeatalysis of the TiO2 nanostructures was characterized by the degradation of RhB dye molecules in an aqueous solution exposed to ultraviolet light. Results show a 7 cm^2 annealed TiO2 flower-like nanostrueture having the degradation rate of RhB as fast as 29.8 times that of the dye solution exposed to ultraviolet light alone.

Degradation of Gesaprim Herbicide by Heterogeneous Photocatalysis Using Fe-Doped TiO2

Fe-doped TiO2 was prepared by the sol gel method and characterized by X-ray diffraction. All the Fe-doped TiO2 were composed of an anatase crystal form. The activity of the Fe-doped TiO2 for the degradation of the gesaprim commercial herbicide (which contains atrazine as active compound and formulating agents) was studied by varying the iron content during UV (15 W), visible light and solar irradiations. The visible light came from commercial saving energy lamps (13, 15 and 20 Watts). The gesaprim degradation rate depended on the iron content in the photo catalyst. The Fe-doped TiO2 (0.5% by weight of TiO2) showed higher TOC removal under visible light and was more active than the undoped TiO2 photo catalyst under the light irradiation sources tested. Over 90% of chemical oxygen demand abatement was achieved with both UV and visible light but less time was required to decrease the chemical oxygen demand content by using the catalyst doped with iron at 0.5% under visible light. It was observed that the degradation of gesaprim increased by increasing the iron content in the catalyst under visible light.

Atomic Ni directional-substitution on ZnIn_(2)S_(4) nanosheet to achieve the equilibrium of elevated redox capacity and efficient carrier-kinetics performance in photocatalysis

It is a challenge to coordinate carrier-kinetics performance and the redox capacity of photogenerated charges synchronously at the atomic level for boosting photocatalytic activity.Herein,the atomic Ni was introduced into the lattice of hexagonal ZnIn_(2)S_(4) nanosheets(Ni/ZnIn_(2)S_(4))via directionalsubstituting Zn atom with the facile hydrothermal method.The electronic structure calculations indicate that the introduction of Ni atom effectively extracts more electrons and acts as active site for subsequent reduction reaction.Besides the optimized light absorption range,the elevation of Efand ECBendows Ni/ZnIn_(2)S_(4) photocatalyst with the increased electron concentration and the enhanced reduction ability for surface reaction.Moreover,ultrafast transient absorption spectroscopy,as well as a series of electrochemical tests,demonstrates that Ni/ZnIn_(2)S_(4) possesses 2.15 times longer lifetime of the excited charge carriers and an order of magnitude increase for carrier mobility and separation efficiency compared with pristine ZnIn_(2)S_(4).These efficient kinetics performances of charge carriers and enhanced redox capacity synergistically boost photocatalytic activity,in which a 3-times higher conversion efficiency of nitrobenzene reduction was achieved upon Ni/ZnIn_(2)S_(4).Our study not only provides in-depth insights into the effect of atomic directional-substitution on the kinetic behavior of photogenerated charges,but also opens an avenue to the synchronous optimization of redox capacity and carrier-kinetics performance for efficient solar energy conversion.

One-Pot Green Synthesis of 1, 4-Dihydropyridine Derivatives Using Polyindole TiO2 Nanocatalyst by Solvent Free Method

This study used a Polyindole in combination with TiO2 nanocatalyst as an efficient heterogeneous catalyst to carry out a multi-component Hantzsch reaction involving different aromatic aldehydes with methyl acetoacetate, and aqueous ammonium to create 1,4-dihydropyridine derivatives under solvent free condition at ambient temperature. A broad range of aldehydes and methyl acetoacetates, ranging from heteroaromatic to polyaromatic one, with high level of functional group tolerance can be used to provide the desired products possessing relevant medicinal moiety in high yields. This technology has prospective advantages over current protocols, including the utilization of a cheap, stable, recyclable, and safe catalyst, quicker reaction times with higher yields and simple product isolation.

Synthesis and Characterization of Rectorite/ZnO/TiO2 Composites and Their Properties of Adsorption and Photocatalysis for the Removal of Methylene Blue Dye

As efficient water treatment agents, a novel series of rectorite-based ZnO and TiO2 hybrid composites（REC/ZnO/TiO2） were synthesized and characterized in this study. Effects of experimental parameters including TiO2 mass ratio, solution p H and catalyst dosage on the removal of methyl blue（MB） were also conducted. The presence of a little mass ratio（2%-6%） of TiO2 highly promoted the photoactivity of REC/ZnO/TiO2 in removal of MB dye from aqueous solution, in which ZnO and REC played a role of photocatalyst and adsorbent. The promotion effects of TiO2 may result from the accelerated separation of electron-hole on ZnO. The observed kinetic constant for the degradation of MB over REC/ZnO and REC/ZnO/TiO2 were 0.015 and 0.038 min^（-1）, respectively. The degradation kinetics of MB dye, which followed the Langmuir–Hinshelwood model, had a reaction constant of 0.17 mg/（L min）. The decrease of removal ratio of MB after five repetitive experiments was small, indicating REC/ZnO/TiO2 has great potential as an effective and stable catalyst.

Preparation and photocatalysis properties of composite photocatalyst CoPcS/TiO2/K2Ti4O9

Photocatalyst CoPcS/TiO2 was prepared by sol-gel method. Composite CoPcS/TiO2/K2Ti4O9 was prepared by dipping. It was incandesced at various temperatures and modification effect was compared. The results showed that optical absorption of sample incandesce at 423K occurred significant red-shift. Light absorption width extended from ultraviolet region to visible region, especially there was an intensive absorption between 600 nm and 680 nm. X-ray diffraction spectrogram showed that TiO2 in sample still maintained anatase crystal form. Under the illumination of visible light, photocatalysis degradation experiment was taken with Eosin B as simulated pollutants. Decoloration rate of Eosin B was much improved. The rate can reach 80% in 300 minutes.

Preparation of TiO2/Bi2O3 Microfibers and Their Photocatalytic Activity

A series of TiO2/Bi2O3 heterojunction microfibers have been fabricated using cotton fibers as bio-templates, and characterized by XRD, SEM and UV-Vis techniques. Results reveal that Bi2O3 in the TiO2/Bi2O3 sample is assigned to monoclinic and tetragonal mix-crystal phase. Fibers lengths can reach several micrometers and diameters range from 0.5 μm to 3 μm. Compared with pure TiO2 and Bi2O3, TiO2/Bi2O3 samples display better absorption in visible light region. Photocatalytic activity was evaluated by degradation of MB under visible light irradiation. TiO2/Bi2O3 microfibers exhibite much higher activity than pure TiO2 and Bi2O3, and 22.84%TiO2/Bi2O3 can achieve the decomposition of about 95%MB, which is attributed to synergistic effects of the strong visible-light absorption of TiO2/Bi2O3 microfibers and the heterojunction formed between TiO2 and Bi2O3.

Photocatalytic Activity of N-doped TiO2 Photocatalysts Prepared from the Molecular Precursor （NH4）2TiO（C2O4）2

We developed a novel approach for the preparation of N-doped TiO2 photocatalysts by calcining ammonium titanium oxalate at different temperatures. The structures of N-TiO2 were characterized by powder X-ray diffraction, infrared spectroscopy, thermogravimetric analysis, N2 adsorption-desorption isotherms, X-ray photoelectron spectroscopy, diffuse reflectance UV-Vis spectroscopy, and scanning electron microscope. The N-doped TiO2 photocatalysts calcined below 700 ℃ are the pure anatase phase but that calcined at 700 ℃ is a mixture of anatase and rutile phases. The doped N locates at the interstitial site of TiO2 which leads to the narrowing of bad gap of pure anatase N-TiO2. Among all photocatalysts, N-TiO2 photocatalysts calcined at 600 and 400 ℃ exhibit the best performance in the photodegradation of methyl orange under the UV light and all-wavelength light illuminations, respectively; however, because of the perfect crystallinity and the existence of anatase-rutile phase junctions, N-TiO2 photocatalyst calcined at 700 ℃ exhibits the highest specific photodegradation rate, i.e., the highest quantum yield, under both the UV light and all-wavelength light illuminations.

Nitrate-group-grafting-induced assembly of rutile TiO2 nanobundles for enhanced photocatalytic hydrogen evolution

In this study,an acid-induced assembly strategy for a rutile TiO2 photocatalyst was proposed on the basis of the treatment of lamellar protonated titanate with a concentrated HNO3 solution.Nitrate groups were successfully grafted onto a TiO2 surface and induced the assembly of rutile TiO2 nanorods into uniform spindle-like nanobundles.The resulting TiO2 product achieved a photocatalytic hydrogen evolution rate of 402.4μmol h^?1,which is 3.1 times higher than that of Degussa P25-TiO2.It was demonstrated that nitrate group grafting caused the rutile TiO2 surface to become negatively charged,which is favorable for trapping positive protons and improving charge carrier separation,thereby enhancing photocatalytic hydrogen production.Additionally,surface charges were crucial to structural stability based on electrostatic repulsion.This study not only developed a facile surface modification strategy for fabricating efficient H2 production photocatalysts but also identified an influence mechanism of inorganic acids different from that reported in the literature.

Absorption and Photocataly tic Degradation of Machine Oil by Exfoliated Graphite-Supported Nanometer TiO2 Material

By loading nanometer anatase onto exfoliated graphite with the sol-gel method, exfoliated graphite-TiO2 composite （EG-TiO2） can be prepared, which can adsorb oil and can also degrade oil. In a technologic condition for preparing EG-TiO2, the impregnated number of times is the most important factor to influence oil-adsorbing capability, that is, when the impregnated number of times increases, the amount of saturation-adsorbed oil decreases. The study of EG-TiO2 photocatalytic degradation of machine oil based on the weight-loss method and infrared spectrum method indicates that EG-TiO2 has obvious effect of photocatalytic degradation for machine oil. Its performance is superior to pure nanometer TiO2 powder because nanometer TiO2 in EG-TiO2 has three-dimension laminar structure and comparatively high adsorption capability.

Black TiO2: What are exact functions of disorder layer

Among the substantial amount of photocatalyst materials,TiO2 has been enthusiastically studied for a few decades due to its outstanding photocatalytic activity and stability.Recently,black TiO2 consisting of approximately 2 nm of thin disorder layer around the surface showed surprisingly high solar hydrogen generation ability.The disorder layer of TiO2 can enhance its light absorption,charge separation,and surface reaction abilities,however exact fundamentals of photocatalytic water-splitting pathways are still ambiguous.Herein,recent progress and investigations on exact functions of disorder layer and its application in photocatalytic CO2 reduction will be discussed.Throughout the comprehensive studies on disorder layer of TiO2,disorder engineering on photocatalyst materials will suggest the further extension of developing solarfuel production technologies.

Synergistic Decolouration of Azo Dye by Pulsed Streamer Discharge Immobilized TiO_2 Photocatalysis

Photocatalyst was prepared by immobilizing TiO2 on glass beads using the traditional sol-gel method. Ultraviolet light （UV） produced by pulsed streamer discharge was then used to induce photocatalytic activity of TiO2 photocatalyst. Decolouration efficiency of the representative azo dye （acid orange 7, AOT） was investigated using the synergistic system of pulsed streamer discharge plasma and TiO2 photocatalysis. The obtained results showed that the decolouration rate of AO7 could be increased by 16.7% under the condition of adding supported TiO2 in the pulsed streamer discharge system, compared to that in the sole pulsed streamer discharge plasma system, due to the synergistic effect of pulsed streamer discharge and TiO2 photocatalysis induced by pulsed streamer discharge. The synergistic system of pulsed streamer discharge and TiO2 photocatalyst was found to have more reactive radicals for degradation of organic compounds in water.

Kinetic Modeling of the Photocatalytic Degradation of Methyl Orange by Supported TiO2

The photocatalytic degradation of methyl orange （MO） in UV/Supported-TiO2 system was investigated and a kinetic model was presented. The experimental results show that the photocatalytic degradation rate is favored by high concentration of dye in solution and is enhanced by the solution temperature. A simple kinetic model has been proposed which can describe the discoloration process in an adequate way. The calculated results obtained were in good agreement with experimental data. The model predicts the concentration of MO during the photocatalytic degradation process.

Synergistic effects in N‐K_2Ti_4O_9/UiO‐66‐NH_2 composites and their photocatalysis degradation of cationic dyes

N-K2Ti4O9/UiO-66-NH2 composites synthesized by a facile solvothermal method have a core-shell structure with UiO-66-NH2 forming the shell around a N-K2Ti4O9 core.Their photocatalytic activities in the degradation of dyes under visible light irradiation were investigated.The N-K2Ti4O9/UiO-66-NH2 composites exhibited higher photocatalytic activity than the pure components.This synergistic effect was due to the high adsorption capacity of UiO-66-NH2 and that the two components together induced an enhanced separation efficiency of photogenerated electron-hole pairs.The mass ratio of N-K2Ti4O9 to ZrCl4 of 3：7 in the composite exhibited the highest photocatalytic activity.Due to the electrostatic attraction between the negatively charged backbone of UiO-66-NH2with the positively charged groups of cationic dyes,the composites were more photocatalytically active for cationic dyes than for anionic dyes.

Preparation of Nitrogen-doped TiO2 Nanoparticle Catalyst and Its Catalytic Activity under Visible Light

N-doped TiO2 nanoparticle photocatalysts were prepared through a sol-gel procedure using NH4C1 as the nitrogen source and followed by calcination at certain temperature. Systematic studies for the preparation parameters and their impact on the structure and photocatalytic activity under ultraviolet （UV） and visible light irra-diation were carried out. Multiple techniques （XRD, TEM, DRIF, DSC, and XPS） were commanded to characterize the crystal structures and chemical binding of N-doped TiO2. Its photocatalytic activity was examined by the deg- radation of organic compounds. The catalytic activity of the prepared N-doped TiO2 nanoparticles under visible light （λ〉400nm） irradiation is evidenced by the decomposition of 4-chlorophenol, showing that nitrogen atoms in the N-doped TiO2 nanoparticle catalyst are responsible for the visible light catalytic activity. The N-doped TiO2 nanoparticle catalyst prepared with this modified route exhibits higher catalytic activity under UV irradiation in contrast to TiO2 without N-doping. It is suggested that the doped nitrogen here is located at the interstitial site of TiO2 lattice.

Metal-doped Mo2C(metal=Fe,Co,Ni,Cu)as catalysts on TiO2 for photocatalytic hydrogen evolution in neutral solution

The neutral hydrogen evolution reaction(HER)is vital in the chemical industry,and its efficiency depends on the interior character of the catalyst.Herein,work function(WF)engineering is introduced via 3d metal(Fe,Co,Ni,and Cu)doping for modulating the Fermi energy level of Mo2C.The defective energy level facilitates the free water molecule adsorption and,subsequently,promotes the neutral HER efficiency.Specifically,at a current density of 10 mA/cm2,Cu-Mo2C exhibits the best HER performance with an overpotential of 78 mV,followed by Ni-Mo2C,Co-Mo2C,Fe-Mo2C,and bare Mo2C with 90,95,100,and 173 mV,respectively,and the corresponding Tafel slope values are 40,43,42,56,and 102 mV/dec.The modified WF can also lead to an enhanced photocatalytic efficiency owing to the lowered Schottky barrier and excellent carrier transition across the electrocatalyst–solution interface.When coupling the metal-doped Mo2C samples with TiO2,enhanced photocatalytic neutral HER rates are obtained in comparison to the case with bare TiO2.Typically,the HER rates are 521,404,275,224,147,and 112μmol/h for Cu,Ni,Co,Fe,bare Mo2C,and bare TiO2,respectively.Time-resolved photoluminescence spectroscopy(TRPS)and ultrafast transient absorption(TA)measurements are carried out to confirm the recombination and migration of the photogenerated carriers.The fittedτvalues from the TRPS curves are 22.6,20.5,10.1,4.7,4.0,2.5,and 1.9 ns for TiO2,TiO2-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,TiO2-Fe-Mo2C,and TiO2-Pt,respectively.Additionally,the fittedτvalues from the TA results are 31,73,and 105 ps for the TiO2-Mo2C,TiO2-Cu-Mo2C,and TiO2-Pt samples,respectively.This work provides in-depth insights into the WF modulation of an electrocatalyst for improving the HER performance.

Enhanced Photoelectrochemical Property of Zn Loaded TiO2 Nanotube Arrays Electrode

TiO2 nanotube arrays （TNTs） electrode loaded with Zn nanoparticles was prepared by anodization and the size of Zn nanoparticle loaded on TNTs electrode was controlled by chronoamperometry deposition time. Results of SEM and XRD analysis show that Zn nanoparticles had a diameter of about 15-25 nm when the deposition time was 3-5 s. The UV-Vis diffuse reflectance spectra show the Zn loaded harvest light with 480-780 nm more effectively than the unloaded sample. The photocurrent response of Zn loaded TNTs electrodes were studied, the results showed that TNTs electrodes loaded with Zn nanoparti-cles has 50% increased photocurrent response under high-pressure mercury lamp irradiation compared with unloaded TNTs electrode.

Rare earth ion modified TiO_2 sols for photocatalysis application under visible light excitation

TiO_2 sols modified by rare earth (RE) ions (Ce^(4+), Eu^(3+), or Nd^(3+))were prepared by coprecipitation-peptization method. The photocatalysis activity was studied byinvestigating the photodegradation effects of active brilliant red dye X-3B. It is found that TiO_2sols modified by Ce^(4+), Eu^(3+), or Nd^(3+) have the anatase crystalline structure, which areprepared at 70℃. All RE^(n+)-TiO_2 sol samples have uniform nanoparticles with similar morphology,which are homogenously distributed in aqueous colloidal systems. The particle sizes are 10, 8, and12 nm for Nd^(3+)-TiO_2, Eu^(3+)-TiO_2, and Ce^(4+)-TiO_2, respectively. The character of ultrafineand positive charge sol particles contributes to the good adsorption of X-3B dye molecule on thesurface of titania (about 30% X-3B adsorption amount). Experimental results exhibit thatRE^(n+)-TiO_2 sol photocatalysts have the capability to photodegrade X-3B under visible lightirradiation. Nd^(3+)-TiO_2 and Eu^(3+)-TiO_2 show higher photocatalytic activity than Ce^(4+)-TiO_2,which is due to the difference of standard redox potential of RE^(n+)/RE^((n-1)+). RE^(n+)-TiO_2sols demonstrate more excellent interfacial adsorption and photodegradation effects to X-3B thanP_(25) TiO_2 crystallites. Moreover, the degradation mechanism of X-3B is proposed as dyephotosensitization and electron scavenging by rare earth ions.

Photocatalysts of Cr Doped TiO2 Film Prepared by Micro Arc Oxidation

A series of Cr doped TiO2 films were prepared by micro arc oxidation （MAO） using an electrolyte of Na3PO4＋K2Cr2O7. X-ray diffraction and scanning electron microscopy revealed that the films mainly consisted of anatase phase with a porous surface morphology. The films have an excellent photocatalytic effect for degradation of methylene blue and decomposition of water under visible light illumination. This arises from the formation of Cr3＋/Cr4＋ and oxygen vacancy energy levels owing to Cr doping. The former reduces the electron-hole recombination chance, while the latter generates a new gap between the conduction band （CB） and valence band （VB） of TiO2, which lowers the photo energy of the excited electron in the VB to the oxygen vacancy states. The mechanisms for film synthesis during the MAO process are also presented.

Photo-depositing Ru and RuO2 on Anatase TiO2 Nanosheets as Co-catalysts for Photocatalytic O2 Evolution from Water Oxidation

TiO2 nanosheets mainly exposed （001） facet were prepared through a hydrothermal process with HF as the morphology-directing agent. Ru and RuO2 species were loaded by photo-deposition methods to prepare the photocatalysts. The structural features of the catalysts were characterized by X-ray di raction, transmission electron microscopy, inductively cou-pled plasma atomic emission spectrum, and H2 Temperature-programmed reduction. The photocatalytic property was studied by the O2 evolution from water oxidation, which was examined with respect to the in uences of Ru contents as well as the oxidation and reduction treatments, suggesting the charge separation effect of the Ru species co-catalysts on di erent facets of TiO2 nanosheets. In contrast to Ru/TiO2 and RuO2/TiO2 with the single deposited co-catalyst, the optimized catalyst 0.5%Ru-1.0%RuO2/TiO2 with dual co-catalysts achieved a much improved catalytic performance, in terms of the synergetic effect of dual co-catalysts and the enhanced charge separation effect.