Mono-doped TiO2 Research Articles

Enhanced photocatalytic performance of (N, F) co-doped TiO2 loaded on coal-based hierarchical porous carbon foam under simulated sunlight

(N, F) co-doped TiO2 was prepared by solvothermal method with urea as N source followed by surface fluorination, and then loaded onto a monolithic coal-based hierarchical porous carbon foam (HPCF). The activity of the synthesized (N, F)–TiO2/HPCF was compared with pure TiO2, N/F mono-doped TiO2 and the unloaded (N, F)–TiO2 for photocatalytic degradation of phenol. Furthermore, the effect of different pore structures of HPCFs on photocatalytic activity was investigated. The results showed that N doping extended the photoresponse of TiO2 to the visible region, while the lattice doping of fluorine greatly improved its UV-light driven activity. The macropores and thin-walled structure of HPCF ensured that the loaded TiO2 could be exposed to the light, and its micro/mesopores enhanced adsorption capacity. As a result, the (N, F) co-doped TiO2 supported on the HPCF with a larger mesoporosity of 21% and a specific surface area of 301.8 m2/g exhibited the highest photocatalytic activity and a stable cyclic usability under simulated sunlight irradiation. This study indicates great potential of the novel (N, F) co-doped TiO2/HPCF composite in photocatalysis for wastewater treatment.

Fe3O4/Co3O4–TiO2 S-scheme photocatalyst for degradation of organic pollutants and H2 production under natural sunlight

Sunlight responsible mono- and co-doped TiO2 nanoparticles (Con+ and Fen+) were prepared via sol–gel technique. The X-ray diffraction (XRD) results showed no phase change of TiO2 was observed after the addition of Con+ and Fen+ ions. Diffuse reflectance spectra (DRS) results showed a significant red-shift of the absorption edge after doping TiO2 by Con and Fen+ and the band gap energy reduced sharply from 3.10 to 1.72 eV. X-ray photoelectron spectroscopy (XPS) results emphasized the existence of multivalent states of Co2+, Co3+, Fe2+ and Fe3+. The results of ultraviolet photoelectron spectroscopy (UPS), work function, electron spin resonance (ESR) illustrated the Fe3O4/Co3O4–TiO2 formed of ternary heterojunctions. The photocatalytic performance of the prepared photocatalysts was determined for photodegradation of tetracycline (TC) and phenol (Pl) and production of hydrogen. The results illustrated the existence of multivalent states of Fe and Co ions (Co2+, Co3+, Fe2+ and Fe3+) together improved the solar light absorption, inhibited the recombination of photogenerated charges and consequently enhanced the photocatalytic efficiency of TiO2 compared with mono-doped TiO2 (Co3O4/TiO2 and Fe3O4/TiO2). The sample with 5%Fe3O4/Co3O4–TiO2 showed the highest photoactivity. The mineralization (TOC), photodegradation mechanism and reusability of prepared photocatalysts were also studied. The Fe3O4/Co3O4–TiO2 nanoparticles showed high photoactivity and stability and can be adopted as a promising materials for different environmental and H2 production applications.

Degradation of 4-Tert-Butylphenol in Water Using Mono-Doped (M1: Mo, W) and Co-Doped (M2-M1: Cu, Co, Zn) Titania Catalysts.

Mono-doped (Mo-TiO2 and W-TiO2) and co-doped TiO2 (Co-Mo-TiO2, Co-W-TiO2, Cu-Mo-TiO2, Cu-W-TiO2, Zn-Mo-TiO2, and Zn-W-TiO2) catalysts were synthesized by simple impregnation methods and tested for the photocatalytic degradation of 4-tert-butylphenol in water under UV (365 nm) light irradiation. The catalysts were characterized with various analytical methods. X-ray diffraction (XRD), Raman, Diffuse reflectance (DR) spectroscopies, Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), and Energy dispersive spectroscopy (EDS) were applied to investigate the structure, optical properties, morphology, and elemental composition of the prepared catalysts. The XRD patterns revealed the presence of peaks corresponding to the WO3 in W-TiO2, Co-W-TiO2, Cu-W-TiO2, and Zn-W-TiO2. The co-doping of Cu and Mo to the TiO2 lattice was evidenced by the shift of XRD planes towards higher 2θ values, confirming the lattice distortion. Elemental mapping images confirmed the successful impregnation and uniform distribution of metal particles on the TiO2 surface. Compared to undoped TiO2, Mo-TiO2 and W-TiO2 exhibited a lower energy gap. Further incorporation of Mo-TiO2 with Co or Cu introduced slight changes in energy gap and light absorption characteristics, particularly visible light absorption. In addition, photoluminescence (PL) showed that Cu-Mo-TiO2 has a weaker PL intensity than undoped TiO2. Thus, Cu-Mo-TiO2 showed better catalytic activity than pure TiO2, achieving complete degradation of 4-tert-butylphenol under UV light irradiation after 60 min. The application of Cu-Mo-TiO2 under solar light conditions was also tested, and 70% of 4-tert-butylphenol degradation was achieved within 150 min.

Effect of Zr-La-TiO2 Catalyst on Denitrification for Coal Combustion

Nanocomposites of TiO2 co-doped with La and Zr were prepared using the microwave-assisted sol-gel method. The samples were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), energy dispersive spectroscopy (EDS) and specific surface area measurement (BET). The XRD results revealed that all the catalysts showed an anatase phase. It was found that the particle size of La-Zr-TiO2 is much smaller than pure TiO2. Moreover, the denitrification efficiency of La-Zr-TiO2 was 65.77%, which was higher than that of the pure and mono-doped TiO2 in the experiment.

First Principle DFT + U Calculations for the Optoelectronic Properties of Cu and C-Cu co-doped TiO2 Anatase Model

The metal-cations and non-metal anions mono-doped titanium dioxide (TiO2) systems have shown limited success as an efficient photocatalyst for various photocatalytic applications. Instead, the co-doping of TiO2 with metal and non-metal dopants is transpired as an effective doping approach to reduce the wide bandgap of the TiO2 and harvest a greater amount of the visible solar spectrum. Herein, a computational study was systematically performed to develop an efficient carbon-copper (C-Cu) co-doped TiO2 anatase system and compared its optoelectronic characteristics with the copper (Cu) mono-doped TiO2 system. The structural properties simulated with Perdew–Burke–Ernzerhof assisted generalized gradient approximation (GGA + PBE) whereas the electronic and optical properties with Hubbard’s modified (GGA + U) approximation. The electronic band structure and density of states plots display reduced bandgap energy of 2.30 eV for the C-Cu co-doped TiO2 anatase model in comparison to Cu mono-doped TiO2 anatase model. Moreover, the absorption spectra display a redshift of the optical absorption edge up to 515 nm for the co-doped system. Overall, the DFT work provide clear insights and predictions that the C-Cu co-doped TiO2 anatase model has an efficient bandgap narrowing with a significant redshift of the optical absorption edge in comparison to Cu mono-doped TiO2 model.

Electronic, Structural, and Optical Properties of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells-A First Principles Study.

Titanium dioxide (TiO2) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO2 polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO2 brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO2 brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO2 brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO2 brookite (210) surfaces.

Optimized preparation and characterization of Co-N codoped TiO2 with enhanced visible light activity: An insight into effect of dopants on surface redox reactions of photogenerated charge carriers for hydroxyl radical formation

In this study, a statistical experiment design approach using response surface methodology was applied in the optimization of preparing Co-N codoped TiO2 photocatalyst. The prepared Co-N codoped TiO2 significantly enhanced the photocatalytic degradation of dye Congo Red under visible light irradiation, as compared to undoped and N, Co monodoped TiO2. As proved by various characterizations, the enhanced photocatalytic activity of Co-N codoped TiO2 can be attributed to the narrowing of energy band structure and the existence of surface oxygen vacancies (OVs) and Co ions as the charge traps, thus resulting in the improvement of visible light absorption and charge transfer. The electron spin resonance and fluorescence measurements confirmed that the formation of hydroxyl radicals (•OH) can be promoted during Co-N codoped TiO2 photocatalysis, due to the more efficient generation and separation of electron–hole pairs. Moreover, it was found that the oxidation of H2O by holes is the relatively major pathway of •OH formation, and OVs could effectively reduce the electron competition between dissolved O2 and Co dopants to ensure the hole- and electron-induced surface redox reactions to proceed smoothly. Based on the above results, a more comprehensive mechanism of Co-N codoping for enhancing TiO2-assisted photocatalysis was thereby proposed.

Enhanced photo-absorption of anatase TiO2 with Ni and Eu doping: A first principle study

In this study, structural, electrical and optical properties of doped and un-doped TiO2 were investigated. Calculations for the analysis of all properties were carried in density functional theory implemented in Wien2k code. Comparison of all the properties was carried of un-doped TiO2, and Ni & Eu doped TiO2. The FP-LAPW was used for description of Kohn-Sham (KS) and properties related to ground state were analyzed. Deformation in the structure was observed due to the ionic radii and electronic configuration of dopant atoms. While analyzing electrical properties, change in the density of the states was observed attributed to the fact of replacement of Ti by Ni and Eu. Band gap was reduced in mono-doped and co-doped TiO2 as a result of which co-efficient of absorption was increased in region of visible light thus making it a potential candidate for applications in the field of solar energy.

Morphology- and Phase-Controlled Synthesis of Visible-Light-Activated S-doped TiO2 with Tunable S4+/S6+ Ratio

In this work, a facile one-pot hydrothermal method was developed to prepare morphology- and phase-controlled S-doped TiO2 with tunable S4+/S6+ ratio. Cheap and convenient metal sulfates were employed as a sulfur source. The metal ions from the sulfates were not doped into TiO2, while they did promote S4+ generation and S4+/S6+ co-doping during the preparation process. Meanwhile, SO42- ions not only acted as a sulfur source,but also controlled the morphology and crystalline phase. The S4+/S6+ ratios of the sulfur-doped TiO2 prepared with Na2SO4, ZnSO4·7H2O, MnSO4·H2O and Fe2(SO4)3 were 1:4.9, 1:5.1, 1:5.2 and 1:5.5, respectively. The visible light photocatalytic efficiency for ciprofloxacin (CIP) degradation of S4+/S6+ co-doped samples was influenced by S4+/S6+ ratio. All of the S4+/S6+ co-doped samples showed enhanced activity compared with S6+ mono-doped TiO2 and undoped TiO2. It can be due to the synergistic effect of the crystalline phase, morphology and S4+/S6+ ratio, of which the S4+/S6+ratio may play the more important role. The TiO2 photocatalyst with a S4+/S6+ ratio of 1:5.5 exhibited the highest visible light photocatalytic efficiency to degrade ciprofloxacin (CIP), which was 2.3 and 8.0 times that of S6+ mono-doped and undoped TiO2, respectively.

Chemical Synthesis and High-Pressure Reaction of Nb5+ Monodoped Rutile TiO2 Nanocrystals

Identifying the doping effects of extrinsic ions both during chemical reactions and in resultant products is important to deeply understand the associated material properties and to develop novel materials for practical applications. Here, we experimentally demonstrate the significant inhibitor effect of Nb5+ dopants on the formation of rutile TiO2 nanocrystals through dopant concentration-modified solvothermal reaction processes. A lower Nb5+ doping level (≤9.09 atom %) is found to be more beneficial for the nucleation and growth of rutile Ti1 – 2x4+Tix3+Nbx5+O2 nanocrystals while a higher one (>9.09 at.%) leads to the preferable formation of the anatase phase. At a pressure range of up to 30 GPa, the synthesized Nb5+ monodoped rutile TiO2 nanocrystals almost possess an equal slope in their respective plot of the pressure-dependent Raman frequency shifts and a similar structural transformation from rutile to baddeleyite-like (pressurization) and then to an α-PbO2-like phase (depressurization). They thus present a dopant concentration-independent high-pressure reaction behavior due to a small change in their average and local defect structures evidenced by the bond valence sum analysis and density functional theory calculations. This work not only emphasizes the key roles of dopants in material synthesis but also broadens insights into the intrinsic correlations between material properties and their specific local defects.

TiO2 Co-doped with Zr and Ag shows highly efficient visible light photocatalytic behavior suitable for treatment of polluted water.

The objective of this study is to analyze the effects of zirconium (Zr) and silver (Ag) doping on the photoactivity of titania (TiO2). Zr–Ag (ZA) co-doped TiO2 products were fabricated via sol–gel technique and their properties (structural and chemical) were characterized. The weight ratio of TiO2 was fixed, while weight ratios of Zr and Ag were varied from 2 to 4, 6 and 8 wt% while synthesized samples were calcined at 400 °C for 3 h. The XRD results demonstrated that the incorporation of metal doping agents failed to alter the host material's lattice structure, however, its crystallite size was reduced from 13.54 to 5.05 nm with increasing Zr4+ and Ag+ concentrations. FTIR spectroscopy was used to examine various functional groups. In the attained spectra, an ample absorption peak between 500 and 1000 cm−1 was recorded, which was ascribed to Ti–O–Ti linkage vibration mode present within TiO2. Surface morphology, microstructure, SAED patterns and elemental composition were examined with FE-SEM, HR-TEM and EDX, which served to confirm the ZA-doped TiO2 product. Band gap energy of the co-doped material was significantly reduced as indicated by a higher wavelength redshift in the spectra. The photoactivity and kinetics of photo-products were investigated by observing photo-decolorization of methylene blue (MB) under a radiation source. Photodecomposition of MB was dramatically enhanced when titania co-doped with Zr and Ag was employed compared to un-doped or mono-doped TiO2. The ZA (8 wt%) co-doped TiO2 photocatalyst depicted the maximum MB removal efficiency (∼93%) within 90 min under a light source.

Visible light photocatalytic activity of tungsten and fluorine codoped TiO2 nanoparticle for an efficient dye degradation

Tungsten and fluorine codoped TiO2 (W, F-TiO2) nanoparticles were synthesis by sol-gel method. The XRD analysis shows that all the samples existed as anatase phase of TiO2. Also, the crystalline size of codoped TiO2 is decreasing than the pure and monodoped TiO2. TEM images indicate that grain size of pure and codoped TiO2 nanoparticles are in the range of 15–22 and 6–14 nm, respectively. Band gap of codoped TiO2 nanoparticles showed narrowing (2.85 eV) when compared to monodoped TiO2 (3.02 and 2.97 eV) and pure (3.16 eV) nanoparticles. The observed lower intensity from PL study in the codoped TiO2 sample than that in other TiO2 samples indicated that the recombination of photoinduced electrons and holes in TiO2 could be effectively inhibited in the W and F ions. The codoped TiO2 exhibited the highest photocatalytic activity under visible light compared with other TiO2. The codoped TiO2, great visible light absorption is produced by the formation of impurity energy states near both the band edges which also act as both the photogenerated charges to diminish the recombination process.

In-situ co-doping of sputter-deposited TiO2:WN films for the development of photoanodes intended for visible-light electro-photocatalytic degradation of emerging pollutants

We report on the magnetron sputtering deposition of in-situ codoped TiO2:WN films intended for electro-photocatalytic (EPC) applications under solar irradiation. By varying the RF-magnetron sputtering deposition parameters, we were able to tune the in-situ incorporation of both N and W dopants in the TiO2 films over a wide concentration range (i.e., 0–9 at. % for N and 0–3 at. % for W). X-ray photoelectron spectroscopy analysis revealed that both dopants are mostly of a substitutional nature. The analysis of the UV-Vis transmission spectra of the films confirmed that the optical bandgap of both TiO2:N and TiO2:WN films can be significantly narrowed (from 3.2 eV for undoped-TiO2 down to ∼2.3 eV for the doped ones) by tuning their dopant concentrations. We were thus able to pinpoint an optimal window for both dopants (N and W) where the TiO2:WN films exhibit the narrowest bandgap. Moreover, the optimal codoping conditions greatly reduce the recombination defect state density compared to the monodoped TiO2:N films. These electronically passivated TiO2:WN films are shown to be highly effective for the EPC degradation of atrazine (pesticide pollutant) under sunlight irradiation (93% atrazine degraded after only 30 min of EPC treatment). Indeed, the optimally codoped TiO2:WN photoanodes were found to be more efficient than both the undoped-TiO2 and equally photosensitized TiO2:N photoanodes (by ∼70% and ∼25%, respectively) under AM1.5 irradiation.

Lifetime Enhancement of Visible Light Induced Photocharges in Tungsten and Nitrogenin situCodoped TiO2:WN Thin Films

We report on one-step in situ codoped TiO2 thin films synthesized by cosputtering. The purpose of this acceptor–donor passivated codoping approach is to overcome the optoelectronic limitations that arise for monodoped TiO2 in photocatalytic applications. To evaluate these added benefits, the TiO2:WN thin films were characterized by different techniques. X-ray diffraction patterns and X-ray photoelectron spectral analysis revealed that both N and W dopants are mostly present in the desired substitutional locations. Additionally, the codoping approach was found to reduce the internal strain and defect density of the TiO2:WN films as compared to their monodoped TiO2:N counterparts. This defect reduction is confirmed via photocharge lifetime variation obtained using visible light flash photolysis time-resolved microwave conductivity measurements (FP-TRMC). Photocharge lifetime analysis indicated the presence of three distinct decay processes: charge trapping, recombination, and surface reactions. These charac...

Electronic and optical properties of Zr, N mono-doped and co-doped anatase TiO2: first-principles calculations

The growth conditions, crystal structural, electronic, optical and photocatalytic properties of undoped, N-, Zr mono-doped TiO2 and four kinds of Zr/N co-doped TiO2 (Zr–N1, Zr–N2, Zr–N3 and Zr–N4) with different Zr and N co-doped positions were investigated by first-principles calculations. It is found that N substituted preferentially for O under Ti-rich conditions. While Zr substituted preferentially for Ti under O-rich conditions, and has the lowest formation energies (−4.56 eV) due to Zr having the same valence electron distribution as Ti. And, co-doped samples prepared in the experiment may contain all co-doped modes; owing to the formation energies of them being very close under Ti-rich or O-rich conditions. On the other hand, the optical absorption threshold and the optical absorption intensity of Zr–N1, Zr–N2 and Zr–N4 co-doped TiO2 are more enlarged than the N mono-doped and Zr–N3 co-doped TiO2, due to the smaller carrier effective mass and the curved and wide impurity level (IL) appearing in the band gap, which not only increase the carrier mobility and reduce the electron–hole recombination, but also reduces the electronic transition energies. Thus, Zr–N1, Zr–N2 and Zr–N4 co-doped configurations can explain the mechanism of visible light absorption and photocatalytic activity enhancement for co-doped TiO2 and give a good explanation of the previous experimental observation.

First-principles study on codoping effect to enhance photocatalytic activity of anatase TiO2

Codopant is an effective approach to modify the bandgap and band edge positions of transition metal oxide. Here, the electronic structures as well as the optical properties of pristine, mono-doped (N/P/Sb) and codoped (Sb, N/P) anatase TiO2 have been systematically investigated based on density functional theory calculations. It is found that mono-doped TiO2 exhibits either unoccupied or partially occupied intermediate state within the energy gap, which promotes the recombination of electron-hole pairs. However, the presence of (Sb, N/P) codopant not only effectively reduces the width of bandgap by introducing delocalized occupied intermediate states, but also adjusts the band edge alignment to enhance the hydrogen evolution activity of TiO2. Moreover, the optical absorption spectrum for (Sb, N/P) codoped TiO2, which is favored under oxygen-rich condition, demonstrates the improvement of its visible light absorption. These findings will promote the potential application of (Sb, N/P) codoped TiO2 photocatalysis for water splitting under visible light irradiation.

Electronic, optical and photocatalytic behavior of Mn, N doped and co-doped TiO2: Experiment and simulation

The crystal phase structure, surface morphology, chemical states and optical properties of Mn, N mono-doped and co-doped TiO2 nanoparticles were investigated by X-ray powder diffractometry, Raman spectra, scanning electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffuse reflectance spectroscopy. Meanwhile, geometry structures, formation energies, electronic and optical properties of all systems have been also analyzed by density functional theory. The results showed that the band gap values and the carrier mobility in the valence band, conduction band and impurity levels have a synergetic influence on the visible-light absorption and photocatalytic activity of the doped TiO2. The number and the carrier mobility of impurity level jointly influence the photocatalytic activity of catalyst under visible-light. Especially, the photocatalytic activity of Mn-2N co-doped TiO2 beyond three-fold than that of pure TiO2 under visible-light.

Efficient Co-B-codoped TiO2 photocatalyst for degradation of organic water pollutant under visible light

Lattice location of B in TiO2 is tuned to determine its effect on the photocatalytic activity of Co-B codoped TiO2. Sol–gel method was used to synthesize the samples. The concentrations of Co and B were first optimized by maximizing the photocatalytic activity for the monodoped (Co or B)-TiO2. In addition to the DFT calculations for discovering new energetic levels introduced in TiO2 by codoping, various characterization techniques were used to determine the dopant lattice sites in TiO2 and interactions between them; and also determining their consequences on electronic, morphological, structural, and optical properties. At low concentration of B-doping (1at.%), B occupies the interstitial site (Bint), but as the concentration increases (2at.% and 3at.%) B also occupies substitutional O position (Bsub) in addition to Bint to form TiO2 containing Bint+sub. Both these B-doped TiO2 showed improved photocatalytic activity attributed to effective charge separation obtained for TiO2–Bint due to the formation of shallow energy level while higher visible light absorption is achieved with TiO2–Bint+sub owing to the presence of two deep energy levels in the band gap as confirmed by DFT calculations. In the case of Co doping, the band gap of TiO2 is reduced but the recombination rates are always high and are caused by the formation of Co states in the band gap. For Co monodoped TiO2, the photocatalytic activity is low for all the concentrations considered, except for very low concentration of Co (0.1at.%). Two opposite effects were observed when small amount of Co (0.1at.%) was codoped with Bint or Bint+sub. In particular, the photocatalytic degradation rate of organic aqueous pollutants (p-nitrophenol and rhodamine B dye) reduces for TiO2–Co–Bint whereas it is enhanced remarkably for TiO2–Co–Bint+sub as compared to (Co or B) monodoped (∼2.1 times) and undoped (∼7.8 times) TiO2. Higher photocatalytic activity observed in Co-doped TiO2–Bint+sub is discussed in terms of the interactions of Co with B at two different lattice positions in TiO2 and the synergistic effect created by higher visible light absorption and the improved charge separation.

Improved visible light photocatalytic activity of fluorine and nitrogen co-doped TiO2 with tunable nanoparticle size

Fluorine and nitrogen co-doped TiO2 (F-N-TiO2) photocatalysts with enhanced photocatalytic activities were facilely synthesized by a simple one-step hydrothermal method using Ti(SO4)2 as an economical precursor, and hydrofluoric acid and ammonia as F and N source, respectively. The structure, morphology, and optical properties of produced nanoparticles were characterized by X-ray diffraction (XRD), N2 adsorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectra (FT-IR) methods. The synergistic effects of F and N doping were systematically examined by changing the molar ratio of F/N. Compared with the un-doped F or N mono-doped TiO2, the co-doped samples exhibited significantly improved photocatalytic performance due to their synergistic effects under visible light. It was shown that F dopant promoted the crystal growth and crystallinity of samples, while N dopant hindered it to some extent, which resulted in the tunable particle size of obtained F-N-TiO2 materials. The effects of F and N dopants on the enhanced photocatalytic activity of modified TiO2 materials were also discussed. The degradation rate of methylene blue (MB) was achieved at 97.31% after 5h reaction under visible light over the optimized sample of FN3.5T. The materials also showed excellent stability according to the recycling tests of the photodegradation of MB.

Ultrasonic-assisted sol–gel synthesis of samarium, cerium co-doped TiO2 nanoparticles with enhanced sonocatalytic efficiency

In this work, pure TiO2 and samarium, cerium mono-doped and co-doped TiO2 catalysts were synthesized by an ultrasonic-assisted sol–gel method and their sonocatalytic efficiency studied toward removal of Methyl Orange as a model organic pollutant from the textile industry. The relationship of structure and sonocatalytic performance of catalysts was established by using various techniques, such as XRD, TEM, SEM, EDX, DRS, and PL. A comparison on the removal efficiency of sonolysis alone and sonocatalytic processes was performed. The results showed that the samarium, cerium co-doped TiO2 catalyst with narrower band gap energy and smaller particle size leads to a rapid removal of pollutant. It was believed that Sm3+ and Ce4+ ions can serve as superficial trapping for electrons at conduction band of TiO2 and prolonged the lifetime of electron–hole pairs. Finally, the effect of synthesis and operational variables on the sonocatalytic activity of co-doped TiO2 catalyst was studied and optimized using response surface methodology as a statistical technique. The results showed that the maximum removal efficiency (96.33%) was achieved at the optimum conditions: samarium content of 0.6wt%, cerium content of 0.82wt%, initial pollutant concentration of 4.31mgL−1, catalyst dosage of 0.84mgL−1, ultrasonic irradiation power of 700W, and irradiation time of 50min.