Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.     

Effect of Processing Parameters on the Optical Properties of TiO<Subscript>2</Subscript>/Ormosil Planar Waveguide

Hybrid TiO₂/ormosil waveguiding films have been prepared by the sol-gel method at low thermal treatment temperature of 150C. The influence of processing parameters including the molar ratios of titanium butoxide (Ti(OBu)₄)/3-glycidoxypropyltrimethoxysilane (GLYMO) and H₂O/Ti(OBu)₄ (expressed as R), especially aging of sol on the optical properties was investigated. The optical properties of films were measured with scanning electron microscope (SEM), UV/VIS/NIR spectrophotometer (UV-Vis), m-line and the scattering-detection method. The results indicate that the film thickness increases with the increase of sol aging time, but the variation of refractive index as a function of sol aging time depends on the relative ratios of GLYMO to Ti(OBu)₄. Higher transmittance and lower attenuation of the planar waveguide can be obtained in the sol with lower Ti(OBu)₄ contents and shorter aging time.     

Controllable incorporation of CdS nanoparticles into TiO<Subscript>2</Subscript> nanotubes for highly enhancing the photocatalytic response to visible light

A constant current electrochemical deposition was employed to incorporate CdS nanoparticles into the TiO₂ nanotube arrays (TiO₂NTs). The size and amount of CdS nanoparticles in TiO₂NTs (CdS@TiO₂NTs) were controllable via modulating current, deposition time and electrolyte concentration. It was revealed, from the scanning electron microscopy (SEM) images and X-ray photoelectron spectroscopy (XPS) in depth profile, that CdS nanoparticles were filled into TiO₂ nanotubes. A shift of the absorption edge toward the visible region under the optimal electrodeposition condition was observed with the diffuse reflectance spectroscopy (DRS). A 5-fold enhancement in the photocurrent spectrum for TiO₂NTs was observed and the photocurrent response range was significantly extended into the visible region because of the CdS incorporation. Compared with pure TiO₂NTs, under a visible light irradiation, CdS@TiO₂NTs exhibited a 3.5-fold improvement of photocatalytic activity, which was demonstrated by the photocatalytic decomposition of Rhodamine B (RhB).     

Advanced Bi<Subscript>2</Subscript>O<Subscript>2.7</Subscript>/Bi<Subscript>2</Subscript>Ti<Subscript>2</Subscript>O<Subscript>7</Subscript> composite film with enhanced visible-light-driven activity for the degradation of organic dyes

Bi₂O_2.7/Bi₂Ti₂O₇ composite photocatalyst films are synthesized by sol–gel dip-coating. The ratio of adding Bi and Ti precursors can be controlled during the preparation process. The phase structure is confirmed by X-ray diffraction. The UV–visible diffuse reflectance spectrum shows that the composite catalysts present light absorption in the visible region. The obtained Bi₂O_2.7/Bi₂Ti₂O₇ composite films possess superior photocatalytic degradation of rhodamine B, owing to the visible light response of Bi₂O_2.7 and the separation of photogenerated electrons and holes between the two components. As a result, the Bi₂O_2.7/Bi₂Ti₂O₇ (Bi/Ti = 1:1) displays the highest photocatalytic activity under visible light or UV light irradiation for the degradation of different organic dyes, including methyl blue, methyl orange and acid orange 7.     

Enhancement of visible-light photocatalytic activity of Cu-doped TiO<Subscript>2</Subscript> nanoparticles

Bare TiO₂ and Cu-doped TiO₂ nanoparticles with different nominal doping amounts of Cu ranging from of 0.5 to 5.0 mol% were synthesized using the modified sol–gel method. The samples were physically characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Brunauer–Emmett–Teller-specific surface area, UV–Vis diffuse reflectance spectroscopy, zeta potential, X-ray photoelectron spectroscopy, inductively coupled plasma, and photoluminescence techniques. The Cu-doped TiO₂ exhibited good photocatalytic activity in mineralization of oxalic acid and formic acid under visible light irradiation. Photomineralization of oxalic and formic acids under visible light irradiation revealed greatly enhanced photoactivity exhibited by the 2.0 mol% Cu-doped TiO₂ photocatalyst compared to bare TiO₂ . The enhanced photocatalytic performance arises from copper ion doping in the TiO₂ structure, leading to an extended photoresponsive range, enhanced photogenerated charge separation, and transportation efficiency.     

Photocatalytic Oxidation Based on Modified Titanium Dioxide with Reduced Graphene Oxide and CdSe/CdS as Nanohybrid Materials

Photocatalytic activity of TiO₂ nanoparticles in the visible light region was enhanced. TiO₂–CdSe and TiO₂–CdSe/CdS nanohybrids were supported on the reduced graphene oxide. These nanohybrid materials were applied as photocatalyst toward oxidation of aromatic alcohols under a mild condition and the molecular oxygen as oxidant. A plausible mechanism for the photocatalytic oxidation was also proposed. Desired nanohybrids were obtained via in situ fixation of CdSe/CdS on the surface of nanosheets of reduced graphene oxide (rGO). Finally, it was modified by TiO₂ sol nanoparticles through a hydrothermal method. The obtained nanomaterials, were characterized by SEM, TEM imaging, XRD, EDAX, DRS and XPS analyses. The size of nanohybrids materials were distributed mostly in a narrow range of 50–65 and 60–75 nm for TiO₂–rGO–CdSe and TiO₂–rGO–CdSe/CdS, respectively. These photocatalysts showed high catalytic activity under visible light irradiation in a short reaction time and even higher selectivity rather than UV irradiation. The yield of catalytic oxidation increased at least 25–30% for TiO₂–CdSe/CdS on rGO, which could be related to its higher light sensitivity and lower energy band gap. The photocatalysts were recycled and reused 8 times without significant loss of their activities due to their stability under visible light.     

Highly transparent silica monoliths embedded with high concentration oxide nanoparticles

Silica monoliths embedded with high concentration of γ-Fe₂O₃ or TiO₂ nanoparticles were prepared by a sol–gel procedure designed according to the inherent properties of oxide colloids. In the first step, highly dispersible oxide nanoparticles were produced using an in situ modification sol–gel strategy. Then, these particles were re-dispersed in silicon alkoxide-containing solution to form a stable colloidal solution. The hydrolysis and condensation reactions of alkoxide were catalyzed by an organic base (morpholine). Due to the large molecule size of morpholine, the electric double layer on the surface of colloidal particles was not compressed by the ionized morpholine molecules. The colloidal solution thus remained stable during the gelation process. Through this procedure, oxide nanoparticles could be immobilized homogeneously in the pores of a silica matrix, forming highly transparent and crack-free monoliths.     

Facile synthesis of TiO<Subscript>2</Subscript>/Ag composite aerogel with excellent antibacterial properties

In this study, the effective TiO₂/Ag composite antibacterial aerogel powder is prepared by facile sol–gel method and ethanol supercritical technology. The surface morphology, structural properties, and chemical components are monitored by scanning electron microscopy (SEM), transmission electron microscope (TEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and energy disperse?spectroscopy (EDS). Meanwhile, absorbance spectra and specific surface area of TiO₂/Ag composite aerogel are characterized by UV-Vis spectra and Brunauer–Emmett–Teller. The TiO₂/Ag composite aerogel with Ti/Ag molar ratios of 10:1, 30:1, 50:1 are measured for its antibacterial property by using Escherichia coliform (E.coli) and Staphylococcus aureus (S. aureus). The results show that the size of TiO₂ and Ag nanoparticles are 40?nm and 25?nm, respectively. Simultaneously, the obtained composite aerogel with a porous structure possessed a surface area of 148?m²/g, an average pore size 11.5?nm, and a pore volume 0.39?cm³/g. With the increase of Ag content, the antibacterial properties of composite aerogel are greatly improved compared with pure TiO₂ aerogel. When Ag/Ti molar ratios was 1:10, the highest antibacterial rate can up to 99%, and the inhibition bands of E. coli and S. aureus are 23?mm and 19?mm, respectively.

Open image in new window

Schematic representation of growth mechanism of TiO₂/Ag composite aerogel (a) and antibacterial performance test (b, c)

     

Synthesis of Three‐dimensionally Ordered Macroporous TiO2 and TiO2/WO3 Composites and Their Photocatalytic Performance

This work presents the characterization and preparation of three‐dimensionally ordered macroporous TiO₂ and TiO₂/WO₃ composite nanoparticles with enhanced visible‐light‐responsive properties for rhodamine B (Rh B) photodegradation. The 3DOM TiO₂ and TiO₂/WO₃ composites were prepared through a dip‐infiltrating sol‐gel process using a polystyrene (PS) colloidal crystal template. The materials were characterized by SEM, TEM, XRD, BET, XPS and UV/Vis. The 3DOM TiO₂/WO₃ composite structures ranged from well‐defined 3DOM structures, which are highly ordered and interconnected via small pore windows, to collapsed three‐dimensional structures as the WO₃ content increased. The photoresponse range and specific surface area of the composite increased with less than 0.025 g of WCl₆. The 3DOM TiO₂/WO₃ composite with less than 0.025 g of WCl₆ exhibited a higher catalytic activity than 3DOM TiO₂ for the photocatalytic degradation of Rh B under simulated sunlight illumination.     

Preparation and photocatalytic activity of TiO<Subscript>2</Subscript> films with Ni nanoparticles

Titania thin films were synthesized by sol–gel dip-coating method with metallic Ni nanoparticles synthesized separately from an organometallic precursor Ni(COD)₂ (COD = cycloocta-1,5-diene) in presence of 1,3-diaminopropane as a stabilizer. Titania was obtained from a titanium isopropoxide precursor solution in presence of acetic acid. A Ni/TiO₂ sol system was used to coat glass substrate spheres (6, 4 and 3 mm diameter sizes), and further heat treatment at 400 °C was carried out to promote the crystallization of titania. XRD analysis of the TiO₂ films revealed the crystallization of the anatase phase. Transmission Electron Microscopy (TEM) and High Resolution TEM studies of Ni nanoparticles before mixing with the TiO₂ solution revealed the formation of Ni nanostructures with an average size of 5–10 nm. High-angle annular dark-field images of the Ni/TiO₂ system revealed well-dispersed Ni nanoparticles supported on TiO₂ and confirmed by AFM analysis. The photocatalytic activity of the Ni/TiO₂ films was evaluated in hydrogen evolution from the decomposition of ethanol using a mercury lamp for UV light irradiation. Titania films in presence of Ni nanoparticles show higher efficiency in their photocatalytic properties in comparison with TiO₂.     

Synthesis of nanostructured titania/zirconia membrane and investigation of its physical separation and photocatalytic properties in treatment of textile industries wastewater

Nanostructured TiO₂/ZrO₂ composite membranes with varying compositions were obtained by sol–gel technique. The influence of 0–30 mol% zirconia doping on microstructure, water permeability, photocatalytic and physical separation properties, removal of methyl violet of textile industries wastewater and thermal and mechanical stability of titania/zirconia composite membranes was described. Firstly, alumina supports were coated with TiO₂ intermediate layers using the colloidal sol–gel route. The TiO₂/ZrO₂ composite sols were prepared via a polymeric sol–gel method and dip-coated on TiO₂ intermediate layer. The samples were characterized by DLS, TG-DTA, XRD, FTIR, BET-BJH, UV–visible, SEM, TEM and AFM. It was shown that zirconia retards the phase transformation of anatase to rutile until at least 700 °C. The minimum pore size and maximum surface area obtained were 1.2 nm and 153 m²/g, respectively, attributed to the sample with 20 mol% zirconia. The mechanical strength of titania membranes was significantly improved by addition of zirconia. The most methyl violet removal efficiency obtained, with and without UV-irradiation, is 80.8 and 72.6%, respectively, attributed to the sample with 20 mol% zirconia.     

Surface properties,adherence, and photocatalytic activity of sol–gel dip-coated TiO2–ZnO films on glass plates

In this study, TiO₂–ZnO nanostructured films prepared from different Ti/water mole ratios were deposited on glass plates by a sol–gel dip-coating method. The structural and surface properties, adherence, and photoactivity of synthesized TiO₂–ZnO coatings in methylene blue degradation were investigated. Among the as-prepared TiO₂–ZnO coatings from sols with different Ti/water mole ratios (1, 0.66, 0.5, and 0.4), the highest sol concentration (Ti/water mole ratio of 1) showed the highest methylene blue photodegradation of almost 80% after 400 min of UV irradiation. X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), Transmission electron microscopy (TEM), Energy-dispersive X-ray (EDX), and UV-vis diffuse reflectance spectra (DRS) confirmed that at high sol concentrations (Ti/water mole ratios of 1 and 0.66), a mixed phase of anatase and rutile is formed, whereas at a Ti/water mole ratio of 0.5, just pure rutile is formed. In detail, decreasing the sol concentration increases the cracks, degree of agglomeration, and the thickness of coatings. UV-vis DRS studies also confirm that decreasing the sol concentration in synthesized TiO₂–ZnO films leads to a shift in the absorption region of the coating to the UV region. Moreover, decreasing the sol concentration declines the coating adherence onto glass plates. TEM images of the TiO₂–ZnO coating synthesized from sol with a Ti/water mole ratio of 1 revealed the formation of ZnO nanorods around a spherical TiO₂, which indicates the presence of strong interaction between TiO₂ and ZnO nanoparticles. The TiO₂–ZnO coating synthesized from sol with a Ti/water mole ratio of 1 was then evaluated at different methylene blue concentrations, pH values, and number of coatings. After five consecutive runs, no significant decrease in the photodegradation efficiency was observed. Scanning electron microscopy (SEM) picture of used coating showed a smooth and stable layer without any detachment. Thermogravimetric analysis (TG) and sonication test confirmed thermal and mechanical stabilities of this coating as well.     

玻璃微珠/Ag/TiO2可见光催化剂的制备与表征

通过离子交换法将Ag纳米颗粒负载于玻璃微珠的表面及浅表层,并以钛酸四丁酯的乙醇溶液为前驱体,将TiO₂负载于包含银的玻璃微珠表面,制得一种玻璃微珠/Ag/TiO₂复合光催化剂。由于纳米银的表面等离子体吸收效应,该复合光催化剂具有一定的可见光响应特性。利用XRD、SEM对样品进行表征,可发现玻璃微珠表面形成一层均匀多孔的锐钛矿TiO₂,其粒径均在50 nm左右。由漫反射光谱可得出该催化剂具有较强的可见光吸收,并在降解甲基橙溶液的试验中表现出较好的可见光催化活性。     

Synthesis of TiO2–SiO2 aerogel via ambient pressure drying: effects of sol pre-modification on the microstructure and pore characteristics

TiO₂–SiO₂ composite aerogels were prepared via ambient pressure drying by sol–gel and surface modification for both the sol and gel samples. The organosilane reagents of decamethyltetrasiloxane (DMTSO)/trimethylchlorosilane (TMCS) and hexamethyldisiloxane (HMDSO)/TMCS were introduced into the TiO₂–SiO₂ composite sol for pre-modification respectively, and subsequently the TMCS/hexane solution was used for surface modification of the obtained TiO₂–SiO₂ composite gel. The effects of sol pre-modification on the microstructure and pore characteristics of TiO₂–SiO₂ composite aerogels were investigated. The results indicate that HMDSO/TMCS coupling reagents is more appropriate for the pre-modification of TiO₂–SiO₂ composite sol than the DMTSO/TMCS reagents. The best volume ratio of HMDSO/TMCS/composite sol for preparing mesoporous TiO₂–SiO₂ composite aerogels is in the range of 1:0.33:10–1:1.0:10, with which the specific surface area and pore volume of the obtained TiO₂–SiO₂ composite aerogels are 492–645 m²/g and 2.63–2.85 m³/g, respectively. The results of adsorption and photocatalytic degradation of rhodamine B show that the as-prepared TiO₂–SiO₂ composite aerogels have higher adsorption/photocatalysis. Particularly, the as-prepared TiO₂–SiO₂ composite aerogels with HMDSO/TMCS showed prominent adsorption capability with the adsorption rate attaining to 89.4 % within 60 min.     

Chemical synthesis of Ni/TiO<Subscript>2</Subscript> nanophotocatalyst for UV/visible light assisted degradation of organic dye in aqueous solution

The Ni/TiO₂ nanoparticles with different Ni dopant content were prepared by a modified sol–gel method. The structure and photoinduced charge properties of the as-prepared catalysts were determined using X-ray diffraction, transmission electron microscopy, UV–vis diffuse reflectance spectroscopy and surface photovoltage spectroscopy techniques, and the photocatalytic efficiency of these catalysts was tested using an organic dye. It was shown that Ni modification could greatly enhance the photocatalytic efficiency of these nanocomposite catalysts by taking the photodegradation of methyl orange as a model reaction. With appropriate ratio of Ni and TiO₂, Ni/TiO₂ nanocomposites showed the superior photocatalytic activity than the single TiO₂ nanoparticles. Surface photovoltage spectra demonstrated that Ni modification could effectively inhibit the recombination of the photoinduced electron and holes of TiO₂. This electron–hole pair separation conditions are responsible for the higher photocatalytic performance of Ni/TiO₂ nanocomposites in the visible region of electromagnetic spectrum.     

Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>/BiFeO<Subscript>3</Subscript> heterostructure: preparation,characterization, and photocatalytic activity

Bi₂O₃/BiFeO₃ composite was successfully fabricated by a conventional sol–gel method and structural properties were characterized based on X-ray diffractometer, scanning electron microscope, transmission electron microscope, energy-dispersive X-ray analyzer, nitrogen adsorption–desorption measurement, and UV–visible diffuse reflectance spectroscopy. Bi₂O₃/BiFeO₃ had a good absorption for visible light, which was benefit to photocatalytic activity. The highest degradation efficiency was obtained when the content of Bi₂O₃ in Bi₂O₃/BiFeO₃ was 63.9%. Effect of experimental conditions was investigated, and the highest photocatalytic activity of Bi₂O₃/BiFeO₃ was observed at photocatalyst dosage of 0.5 g/L, initial BPA concentration of 10 mg/L, and solution pH of 6.3. Bi₂O₃/BiFeO₃ photocatalyst exhibited enhanced photocatalytic activity for BPA, and the reaction rate constant over Bi₂O₃/BiFeO₃ composite was 2.23, 3.65, and 8.71 times higher than that of BiFeO₃, Bi₂O₃ and commercial TiO₂ (P25), respectively. Bi₂O₃/BiFeO₃ showed high photocatalytic activity after three cycles, suggesting that it was a stable photocatalyst. The possible photocatalytic mechanism has been discussed on the basis of the theoretical calculation and the experimental results. The hydroxyl and superoxide radicals together with photogenerated holes played significant roles in the photocatalytic reaction.     

In situ growth of TiO2 in interlayers of expanded graphite for the fabrication of TiO2-graphene with enhanced photocatalytic activity

We present a facile route for the preparation of TiO₂–graphene composites by in situ growth of TiO₂ in the interlayer of inexpensive expanded graphite (EG) under solvothermal conditions. A vacuum‐assisted technique combined with the use of a surfactant (cetyltrimethylammonium bromide) plays a key role in the fabrication of such composites. Firstly, the vacuum environment promotes full infusion of the initial solution containing Ti(OBu)₄ and the surfactant into the interlayers of EG. Subsequently, numerous TiO₂ nanoparticles uniformly grow in situ in the interlayers with the help of the surfactant, which facilitates the exfoliation of EG under the solvothermal conditions in ethanol, eventually forming TiO₂–graphene composites. The as‐prepared samples have been characterized by Raman and FTIR spectroscopies, SEM, TEM, AFM, and thermogravimetic analysis. It is shown that a large number of TiO₂ nanoparticles homogeneously cover the surface of high‐quality graphene sheets. The graphene exhibits a multi‐layered structure (5–7 layers). Notably, the TiO₂–graphene composite (only 30 wt % of which is TiO₂) synthesized by subsequent thermal treatment at high temperature under nitrogen shows high photocatalytic activity in the degradation of phenol under visible and UV lights in comparison with bare Degussa P25. The enhanced photocatalytic performance is attributed to increased charge separation, improved light absorbance and light absorption width, and high adsorptivity for pollutants.     

Sol–gel preparation and characterization of Ag and Mg co-doped nano TiO<Subscript>2</Subscript>: efficient photocatalytic degradation of C.I. Acid Red 27

In this study, we successfully prepared pure, mono-doped, and Ag, Mg co-doped TiO₂ nanoparticles using the sol–gel method, with titanium tetraisopropoxide as the Ti source. The prepared samples were characterized by X-ray powder diffraction (XRD), specific surface area and porosity (BET and BJH) measurement, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, photoluminescence, and energy dispersive X-ray spectroscopy techniques. The XRD data showed that the prepared nanoparticles had the same crystals structures as the pure TiO₂. Also, DRS results indicated that the band gap of co-doped photocatalyst was smaller than that of the monometallic and undoped TiO₂ and that there was a shift in the absorption band towards the visible light region. Furthermore, the photocatalytic activity of the prepared catalysts was evaluated by the degradation of C.I. Acid Red 27 in aqueous solution under visible light irradiation. The results showed that Ag (0.08 mol%), Mg (0.2 mol%) co-doped TiO₂ had the highest photoactivity among all samples under visible light. It was concluded that co-doping of the Ag and Mg can significantly improve the photocatalytic activity of the prepared photocatalysts, due to the efficient inhibition of the recombination of photogenerated electron–hole pairs. The optimum calcination temperature and time were 450 °C and 3 h, respectively.     

CdS/TiO2纳米管复合结构的制备与光电性能研究

利用阳极氧化法在钛金属基体表面制备一层TiO₂纳米管阵列薄膜, 然后通过水热反应在TiO₂纳米管上负载CdS纳米粒子, 形成CdS/TiO₂纳米管的复合结构。利用SEM、XRD、XPS、UV-Vis等手段对其形貌和结构进行表征。进一步考察了CdS/TiO₂纳米管的光电性能和光催化活性, 结果表明, 相比于TiO₂纳米管, CdS/TiO₂纳米管复合结构在紫外光和可见光下都具有更好的光催化活性及光电性能。     

Metal–metal charge transfer and interfacial charge transfer mechanism for the visible light photocatalytic activity of cerium and nitrogen co-doped TiO2

Nanosized cerium and nitrogen co-doped TiO₂ (Ce–TiO_2?xN_x) was synthesized by sol gel method and characterized by powder X-ray diffraction (PXRD), X-ray photoelectron spectroscopy (XPS), FESEM, Fourier transform infrared, N₂ adsorption and desorption methods, photoluminescence and ultraviolet–visible (UV–vis) DRS techniques. PXRD analysis shows the dopant decreases the crystallite sizes and slows the crystallization of the titania matrix. XPS confirm the existence of cerium ion in +3 or +4 state, and nitrogen in ?3 state in Ce–TiO_2?xN_x. The modified surface of TiO₂ provides highly active sites for the dyes at the periphery of the Ce–O–Ti interface and also inhibits Ce particles from sintering. UV–visible DRS studies show that the metal–metal charge transfer (MMCT) of Ti/Ce assembly (Ti⁴⁺/Ce³⁺ → Ti³⁺/Ce⁴⁺) is responsible for the visible light photocatalytic activity. Photoluminescence was used to determine the effect of cerium ion on the electron–hole pair separation between the two interfaces Ce–TiO_2?xN_x and Ce₂O₃. This separation increases with the increase of cerium and nitrogen ion concentrations of doped samples. The degradation kinetics of methylene blue and methyl violet dyes in the presence of sol gel TiO₂, Ce–TiO_2?xN_x and commercial Degussa P25 was determined. The higher visible light activity of Ce–TiO_2?xN_x was due to the participation of MMCT and interfacial charge transfer mechanism.