Photocatalytic Activity Of N-doped TiO2 Research Articles

Preparation and enhanced photocatalytic performance of N-TiO2/g-C3N4 heterostructure for Rhodamine B degradation

Highly efficient photocatalysts have been developed for the degradation of contaminated water under visible light. In this study, N-doped TiO2 (N-TiO2) and metal-free graphitic carbon nitride (g-C3N4) composites with various Ti/C molar ratios were prepared with the simple mixing-calcining method. The samples were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet–visible diffuse reflectance spectroscopy, and photoluminescence spectroscopy. The photocatalytic activity of N-TiO2/g-C3N4 in the degradation of Rhodamine B (RhB) was investigated, and the electrochemical method was used to determine the origin of the enhanced photoactivity of N-TiO2/g-C3N4. The results showed that N-TiO2 nanoparticles were dispersed on the surface of g-C3N4 and formed a stable heterojunction structure with g-C3N4. The heterojunction between the two semiconductors could effectively prevent the recombination of photogenerated electrons and holes and improve the photocatalytic efficiency of the photocatalyst under visible light irradiation. The photocatalyst exhibited high stability, and the RhB degradation rate was still higher than 82.3% after five cycles.

A New Combination Method of N-doped TiO2 Nanoparticles Synthesis for Heavy Metal Ions Cr(VI) Photoreduction Applications

Through a combination of biosynthetic and hydrothermal methods, N-doped TiO2 photocatalyst has been successfully synthesized using various concentrations of ammonia as a nitrogen source, namely 10% w/w (NTO10), 20% w/w (NTO20), 35% w/w (NTO35), and 50% w/w (NTO50). The synthesis of TiO2 was conducted using Aloe vera (L) Burm F. rind extract as a natural capping agent via the biosynthetic method, followed by a nitrogen doping process via the hydrothermal method. The X-ray Diffraction (XRD) analysis revealed that all phases were anatase. According to the results of the UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS) analysis using the Tauc-Plot method, all N-doped TiO2 samples showed a decrease in the energy gap compared to the TO sample. This indicates that the doping of TiO2 using nitrogen has been successfully doped into TiO2. The photocatalytic activity of N-doped TiO2 was evaluated for the photoreduction of the Cr(VI) model pollutant using a 24-watt LED lamp as a visible light source for 120 minutes. The results indicate that the NTO35 is the best-prepared N-doped TiO2, which showed a reduced rate for the Cr (VI) model pollutant of 50.88%, or two times greater than that of undoped TiO2.

Synthesis, Properties and Application of Titanium Dioxide Doped with Nitrogen. Its Effectiveness on Photo Degradation Glutathione-S-Transferase (GST) enzymes Pupae Instar of Aedes aegypti

The sol-gel method was used to create N-doped TiO2. From the characterization results, it was found that N-doped TiO2 using Titanium(IV) ammonia solution and calcination tetraisopropoxide 600 K provided the most appropriate properties for acting as the photo catalyst can be use as inhibitor of GST. SEM, AFM and XRD results indicated that this N-doped TiO2 catalyst had high crystallinity because its titania precursor was simply hydrolyzed completely so no organic contents blocked initial phase construction. SEM and AFM results demonstrated that its surface morphology was spherical like fluffy powders. Moreover, with increasing calcination temperature, its anatase-to-rutile phase transformation was retarded by the incorporated nitrogen. Elemental Analysis and UV-Vis/DR results also suggested that nitrogen could be dormant in the TiO2 lattice with strong bonds, causing the effect on the band gap structure by adding energy states nearly valence band of TiO2. All of these properties enhanced the photocatalytic activity of N-doped TiO2 under visible light. Regarding the photocatalytic activity, N-doped TiO2 with ammonia solution of titanium(IV), calcinated 600 K Tetraisopropoxide succeeded in degrading glutathione-S-transferase (GST) enzymes, with the highest efficiency. However, its photocatalytic activity was drastically decreased when it was calcined at higher temperature. Additionally, the plausible mechanism was also proposed in case of photo degradation of antioxidant content based on two detected intermediates by The association between ln Co/C and photo degradation period (h).

Influence of N sources on the photocatalytic activity of N-doped TiO2

Influence of nitrogen precursors urea, semicarbazide and N,N’-dimethyl urea on the photocatalytic activity of the N-doped TiO2 were studied by a simple decomposition method. The nano N-TiO2 catalysts were synthesized via two different modified approaches by calcination at 500 °C. The synthesized samples were characterized by IR, UV-DRS, Raman, TG-DTA, XRD, EDX, XPS, SEM, TEM and BET analysis. Of the synthesized six samples of N-TiO2 five samples showed better photocatalytic activity towards direct sunlight photo-degradation of methylene blue (MB) and rhodamine B (RhB) than Degussa P25. The catalysts obtained using semicarbazide samples F3 and F4 having large surface area of 76 and 85.8 m2/g displayed maximum photocatalytic activity. The sample F4 was 1.5 times more active than Degussa P25 for the decolourisation of MB and 1.9 times more active for the decolourisation of RhB. The presence of nitrogen, large surface area and coupling of rutile-anatase phases were found to be the main responsible factors for the enhanced photocatalytic activity. The exclusive formation of the anatase phase in the case of urea precursor is attributed to the slow evaporation of urea due to the formation of melamine derived products. The calcination temperature is the deciding factor responsible for the photocatalytic activity of the N-TiO2 samples prepared from precursors which can potentially form the melamine and its oligomerized products on the surface of TiO2.

Solar Photocatalytic Degradation of Diclofenac by N-Doped TiO2 Nanoparticles Synthesized by Ultrasound

Anatase N-doped TiO2 nanoparticles were synthesized using ultrasound at low frequency and room temperature. The samples characterized by techniques including XRD, TEM, HRTEM, FT-IR, XPS, and UV–Vis spectroscopy. XPS indicated the existence of nitrogen as an anion dopant within the TiO2 lattice. The solar photocatalytic activity of N-doped TiO2 studied for the degradation and complete mineralization of Diclofenac (DCF). The results showed that the catalytic activity of the nanoparticles related to the operating conditions in the synthesis such as temperature and time of sonication. DCF degradation followed the pseudo-first-order kinetics model under different conditions. Results showed that photogenerated electrons on the catalyst surface played an important role in the mechanism of photocatalytic degradation of DCF. It also confirmed that in the presence of oxygen, the formation of oxidative species such as singlet oxygen and superoxide radicals had major roles in the degradation of DCF.

Preparation of nitrogen-doped TiO2 nanotube deposited with gold nanoparticles for photocatalytic phenol degradation under visible light

One of the many functions of TiO2 photocatalysts is degrading organic compounds. TiO2 photocatalysts have a band gap of 3.2 eV, which is equivalent to the energy of ultraviolet (UV) photons with a wavelength of 388 nm and allows them to be effectively activated only by UV light. However, they are less effective under visible (Vis) light. Researchers have developed many ways to use the photocatalytic properties of TiO2 under visible light via nitrogen doping. Further, the photocatalytic activity of N-doped TiO2 can be improved via surface plasmon resonance. In this study, N-doped TiO2 nanotubes (N-TiO2 NTs) are prepared and deposited with Au nanoparticles (Au/N–TiO2 NTs) via electrodeposition. The TiO2 NTs and Au/N-TiO2 NTs are characterized using UV-VIS spectrometry, Fourier transform infrared spectroscopy (FTIR), X-ray diffractometry (XRD), field emission scanning electron microscopy, energy dispersive spectroscopy (EDS), and linear sweep voltammetry (LSV). The photocatalytic test under tungsten lamp illumination of a 20-ppm phenol solution in a batch reactor shows a phenol degradation of 60 %, whereas a 20-ppm bisphenol A (BPA) solution is degraded by 40 %.

Synergistic effect of polychromatic radiation on visible light activity of N-doped TiO2 photocatalyst

In this paper, we show a synergistic effect of polychromatic radiation on the visible light activity of a TiO2 photocatalyst doped with nitrogen. This effect consists in the fact that N-doped TiO2 has no photocatalytic activity under red light, but a combination of blue and red lights enhances the utilization of blue light in the photocatalytic oxidation process and substantially increases the photocatalytic activity of N-doped TiO2. This study shows the great potential of N-doped TiO2 photocatalysts for efficient oxidative degradation of pollutants under solar light, which is a polychromatic radiation with a wide range of wavelengths.

Synergism of oxygen vacancies, Ti3+ and N dopants on the visible-light photocatalytic activity of N-doped TiO2

N-doped TiO2 photocatalyst with abundant oxygen vacancies (N-TiO2-x) has been fabricated by a novel solvothermal route (using HNO3 as a nitrogen source) combined with a solid-state chemical reduction method for the first time. Using this combined technology, high-quality N-TiO2-x photocatalyst with small mean particle size (around 7.1 nm) and high surface area (181.7 m2/g) can be acquired. The electron paramagnetic resonance and X-ray photoelectron spectrometer results indicate that oxygen vacancy and Ti3+ are produced in N-TiO2-x during solid-state chemical reduction process. Control experiments show that compare to pristine N-doped TiO2 and pure TiO2, the reduction activated N-TiO2-x catalyst has a great improvement in both optical absorption and photocatalytic performance. It suggests that the N-TiO2-x band-gap narrowing results from synergetic effect of Ti3+ and oxygen vacancies defect energy state belts, as well as N2p midgap state. These energy levels result in enhanced visible light absorption and serve to trap the photogenerated electrons, consequently improving both charge separation and the quantum efficiencies of N-TiO2-x catalysts.

Preparation and visible-light photocatalytic activity of N-doped TiO2 by plasma-assisted sol-gel method

Abstract N-doped TiO2 was synthesized by a facile so-gel method using urea as nitrogen resource. To seek the efficient N doping of TiO2 photocatalysts, non-thermal N2 plasma was employed to treat N-doped TiO2 followed by calcination (N-TiO2 (NTP)) and compared with the conventional calcination (N-TiO2). The samples were evaluated under visible light irradiation for photocatalytic degradation of methyl orange (MO). To elucidate the plasma treatment effect, XRD, SEM, EDS, TEM, BET, UV–vis DRS, FT-IR and XPS techniques were used for catalyst characterization. N-TiO2 (NTP) possessed small particle size of 4.9 nm with better dispersion and narrow band gap of 1.6 eV. The visible-light photocatalytic activity of N-TiO2 (NTP) was much better than that of N-TiO2. And the photocatalytic degradation kinetics of the MO fitted with the Langmuir-Hinshelwood equation. The apparent reaction rate constant of N-TiO2 (NTP) was about 2.8 times as high as that of N-TiO2. The enhancement was ascribed to small particle size of N-doped TiO2 offering more surface active sites and high content of surface oxygen.

Optimization of the photocatalytic activity of N-doped TiO2 for the degradation of methyl orange

Optimization of the photocatalytic activity of N-doped TiO2 for the degradation of methyl orange

Concurrent role of metal (Sn, Zn) and N species in enhancing the photocatalytic activity of TiO2 under solar light

TiO2 modification by both non-metal and metal species is a popular strategy to promote the semiconductor visible light absorption and photocatalytic performance. In this work, tin and zinc are compared as metal promoters to enhance the photocatalytic activity of N-doped TiO2 under solar light. The synthesized samples were tested under both UV and simulated solar irradiation toward the photocatalytic degradation of tetracycline, an emerging water pollutant. All copromoted samples (N + Sn and N + Zn) revealed higher efficiency under solar light in the mineralization of the pollutant with respect to both the pristine and N-doped ones. The enhanced photocatalytic efficiency of these samples was traced back to the modifications introduced by the different guest species to the structural (X-ray Powder Diffraction, XRPD), morphological (High-Resolution Transmission Electron Microscopy, HR-TEM and Brunauer-Emmett-Teller analysis, BET), spectroscopic (X-ray Photoelectron Spectroscopy, XPS, Energy Dispersive X-ray Spectroscopy, EDX and Diffuse Reflectance Spectroscopy, DRS) and surface features (ζ-potential). In this regard, the increased surface area, the modifications of the phase composition and the enhanced visible light harvesting seem to play a pivotal role in affecting the photocatalytic performance. Mass spectrometry analyses allowed us to identify several reaction intermediates and propose different degradation mechanisms depending on the type of metal promoter.

Photocatalytic Activity of N-Doped TiO2 to Vehicle Exhaust in Road Tunnel

Abstract The nitrogen (N)-doped titanium dioxide (TiO2) was synthesized to use as raw materials of coating on the tunnel lining and pavement to purify vehicle exhaust (VE) in a road tunnel. To study photocatalytic activity of N-doped TiO2 to VE, its morphology, surface area, and optical properties were characterized. Then photocatalytic activity tests of TiO2 to VE were conducted under ultraviolet (UV) and visible light irradiation, respectively. Results indicated that the prepared TiO2 showed spherical nanoparticles with the grain size range of 13–16 nm and the agglomeration of TiO2 nanoparticles was decreased with the increase in N-dopant concentration. Synthesized pure and N-doped TiO2 only contain an anatase phase. Also, N-doped TiO2 exhibited higher optical absorptions in UV and visible light region, and the optical absorption edges of N-doped TiO2 present obvious red shift. Additionally, N-doped TiO2 showed higher photocatalytic activity to VE than pure TiO2 under UV and visible light irradiation. The degradation efficiencies of N-doped TiO2 to NOx and HC were higher than those to CO2 and CO in VE under UV light irradiation because of the reversible reaction between CO2 and CO. Furthermore, N-doped TiO2 showed a higher photocatalytic activity to CO2 than that to CO under visible light irradiation, but the reversible reaction was not found. All photocatalytic reactions followed the first-order kinetics in the photocatalytic degradation of VE. It is believed that the N doping is a promising method to improve the photocatalytic activity of TiO2 to VE under visible light irradiation for the air purification in a road tunnel.

Facile and large-scale preparation of N doped TiO2 photocatalyst with high visible light photocatalytic activity

High visible light photocatalytic activity of N-doped TiO2 (N-TiO2) photocatalysts were prepared by facile sol-gel method in large-scale without separation, purification and thermal treatment at high temperature. Ammonium nitrate (AN) was used as nitrogen source and solid substrates, hydrous TiO2 deposited onto the surface of AN micro-particles during the formation of compound gel. AN thermal decomposed and N-TiO2 photocatalysts were obtained by compound dry gel (CDG) calcined at low temperature. N element thermal diffused enter into lattice of TiO2, and the effects of AN evidently facilitated the product transformation from amorphous to anatase. Meanwhile, the doped N element promoted the formation of doping level and its light absorption edge extended to visible region. We systematically research the doping ratio of AN, the different calcined time at low temperature to prepare N-TiO2 with high photocatalytic activity in visible region. As-prepared N-TiO2 photocatalysts exhibited excellent photocatalytic activity under the illumination of visible light, and the photodegradation reaction rate constant was approximately 6 times higher than pure TiO2 samples.

Preparation and Study on Photocatalytic Activity of N-doped TiO2 Decorated N-doped graphene

Titanium dioxide (TiO2) is generally considered to be one of the most promising photocatalysts in the purification of organic pollutants in air or water. To improve its performance, N-doped TiO2 samples decorated with N-doped graphene are prepareted via sol-gel method. The samples are characterized by XRD, XPS and SEM. The photocatalytic activity of the composite materials is evaluated by photocatalytic degradation of methylene blue aqueous solution, a typical organic pollutant. The experimental results are as follows: 1) the samples or the N-graphene/N-TiO2 composite materials have better degradation efficiency than TiO2 doped with N element; 2) Either too much or too little loading of graphene is not conducive to the photocatalytic efficiency of composite materials; 3) Temperature actually affects the optimal loading of graphene; 4) N-RGO (0.5wt%)/N-TiO2-400℃ has the highest photocatalytic efficiency and good stability.

Enhanced visible-light responsive photocatalytic activity of N-doped TiO2 thoroughly mesoporous nanofibers

Improving the photocatalytic efficiency of TiO2 semiconductor is crucially important and highly desired for its practical applications. In the present work, aiming to broaden the photoresponse window and limit the photocatalyst aggregation, we reported the exploration of N-doped TiO2 thoroughly mesoporous nanofibers with high purity in morphology via a foaming-assisted electrospinning strategy. The foaming agents and urea were introduced in the raw materials to create the mesopores and incorporate the N dopants into the conventional solid TiO2 nanofibers, respectively, which could be accomplished simultaneously over one-step calcination process. The synergetic combination of N dopants and one-dimensional mesoporous nanostructure allow the TiO2 fibers to exhibit significantly enhanced visible-light photocatalytic activity toward the Rhodamine B and hydrogen evolution, as compared to those of N-doped solid and intrinsic thoroughly mesoporous counterparts, suggesting their promising applications in water purification and energy supply.

Photocatalytic removal of atrazine using N-doped TiO2 supported on phosphors

Visible light-active N-doped TiO2 (N-TiO2) was successfully immobilized on ZnS-based phosphors microparticles (ZSP) by a modified sol–gel method. Core-shell catalysts were prepared to serve as “photoactive support”, able to harvest the external irradiation and to emit a luminescence with wavelength suitable for activation of N-doped TiO2. The nominal loading of N-TiO2 on ZSP was in the range of 15–50wt% and the effect of the progressive increase in N-TiO2 loading on the coverage of phosphors particles was evaluated. The preparation method did not induce alterations of the initial ZSP crystallographic structure and allowed to obtain N-TiO2 dispersion on ZSP surface. By varying the N-TiO2 loadings on the surface of ZSP, its morphology gradually evolved from pseudo-spherical shape, until 30wt% N-TiO2 loading, to elongated shape for an N-TiO2 content of 50wt%. The photocatalytic activity of N-TiO2/ZSP was evaluated for the removal of atrazine under UVA light irradiation. Enhanced performance compared to either pure N-TiO2 nanoparticles or bare ZSP was observed. The photocatalyst N-TiO2/ZSP at 30wt% of N-TiO2 loading (30N-TiO2/ZSP) demonstrated the highest photocatalytic activity. Photocatalytic performances were strongly dependent on the concentration of catalyst and the initial pH of solution. The optimal catalyst concentration was 0.5gL−1 and the optimal initial pH was 5.8. A study of the reaction intermediates during the photocatalytic removal of atrazine was carried out, evidencing that the sequence of intermediates for 30N-TiO2/ZSP and for the phosphors ZSP alone included dealkylation reactions and alkyl chain oxidation.

Effect of calcination on the visible light photocatalytic activity of N-doped TiO2 prepared by the sol-gel method.

A series of N-doped TiO2 nanoparticle powders have been prepared by the sol-gel method using triethylamine as N precursor. The effect of calcination temperatures on the quality of the as-prepared samples was studied and an annealing treatment was introduced to improve further the quality of the as-prepared sample. The visible light photocatalytic activities of the samples were evaluated by decomposition of methyl orange (MO) in water. The calcination temperature plays a key role in determining the quality of N-doped TiO2 nanoparticle powders. The enhancement of calcination temperatures facilitates the crystallization of N-doped TiO2 powders and the elimination of surface organic residues, but promotes the loss of doping N and the agglomeration of nanoparticles and results in low N doping level and large particle sizes. The N-doped TiO2 sample (NT-300) calcined at 300 degrees C in air for 3 h produced the maximum visible light photocatalytic activity. The annealing treatment of NT-300 at its calcination temperature could improve the crystallinity, remove effectively the surface organic residues, keep nanoparticles in smaller size, and retain the doping N, therefore improving the visible light photocatalytic activity significantly.

Electro-Optic Modulation Induced Enhancement in Photocatalytic Activity of N-Doped TiO2 Thin Films

In the presence of ultraviolet light, TiO2 photocatalyst finds a lot of applications in degradation of organic and inorganic particles present in environment as well as in water. TiO2 nanoparticles can not be utilized effectively in presence of solar light since solar radiation has very little contribution in UV region. The photoresponse of TiO2 can be shifted to the visible region by nitrogen doping. In the nitrogen-doped TiO2 lattice, the oxygen vacancies are formed below the conduction band in the form of donor energy level. These vacancies increase with increasing nitrogen concentration in TiO2, which results in an increase in the trapping rate. This leads to enhancement of photocatalytic activity of nitrogen-doped TiO2 film. Nitrogen doping results in the creation of defects in nitrogen-doped TiO2, which in other way leads to a modification of the work function of thin films. The observed changes in work function of these films, measured using scanning Kelvin probe microscopy, indicates the shifting of Fermi level with the introduction of defects. The study of work function as well as surface properties of thin films helps in better understanding of the photo activity of nitrogen-doped TiO2 film.

Sonochemical Synthesis, Characterization, and Photocatalytic Activity of N-Doped TiO2Nanocrystals with Mesoporous Structure

N-Doped TiO2nanocrystals were synthesized via a simple sonochemical route, using titanium tetrachloride, aqueous ammonia, and urea as starting materials. The as-synthesized samples were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) equipped with an energy dispersion X-ray spectrometer (EDS), transmission electron microscopy (TEM), UV-vis diffuse reflection spectroscopy, Raman spectroscopy, and nitrogen adsorption-desorption isotherms. The results of TEM and nitrogen adsorption-desorption showed that the average size and specific surface area of the as-synthesized nanocrystals are 10 nm and 107.2 m2/g, respectively. Raman spectral characterization combined with the results of XRD and EDS revealed that N dopant ions were successfully doped into TiO2. Compared with pure TiO2, the adsorption band edge of N-doped TiO2samples exhibited an obvious red shift to visible region. The photocatalytic activities were evaluated by the degradation of Rhodamine B (RhB) under visible light, and the results showed that the N-doped TiO2sample synthesized by an optimal amount of urea exhibited excellent photocatalytic activity due to its special mesoporous structure and the incorporation of nitrogen dopant ions.

Fabrication of nitrogen-doped TiO2 monolith with well-defined macroporous and bicrystalline framework and its photocatalytic performance under visible light

Abstract In this study, hierarchically porous bicrystalline nitrogen-doped titania (N-doped TiO 2 ) monolithic material was fabricated by a simple two-step approach: (i) preparation of TiO 2 porous monolith by a sol–gel process of titanium alkoxide in a mild condition utilizing a chelating agent and mineral salt and (ii) annealing of TiO 2 porous monolith obtained under a modest flow of ammonia gas at 700 °C for 2 h. The phase composition, crystal structure, morphology, pore structure, and porous properties of the final product were studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury porosimetry, and nitrogen physisorption measurement, respectively. The resultant N-doped TiO 2 porous monolith possesses a bicrystalline (anatase and rutile) framework with a well-defined macroporosity. The results from X-ray photoelectron spectroscopy (XPS) confirm the formation of O Ti N bonds in the N-doped TiO 2 porous monolith. The photocatalytic activity of N-doped TiO 2 porous monolith was evaluated by the photodegradation of Rhodamine B over the samples under visible light. Nearly 50% of Rhodamine B in aqueous solution was efficiently degraded by N-doped TiO 2 porous monolith with the mixed-phase of anatase and rutile under visible light within 120 min.