Co-doped Titania Photocatalysts Research Articles

Preparation, characterization of co-Ni co-doped titania photocatalyst and its application for the photocatalytic degradation of textile and PPCPs industrial wastewater under sunlight

The undoped TiO2 (T), 1% Ni-doped TiO2 (N1T), and 1% Co–1% Ni co-doped TiO2 (C1N1T) photocatalysts were prepared by the sol–gel technique. The characterization of prepared materials was carried out by X-ray diffraction, Diffused Reflectance Spectroscopy, Scanning Electron Microscopy, Fourier Transform Infrared Spectroscopy, Brunauer–Emmett–Teller and Thermogravimetric Analysis to analyze composition, phase, morphology, and optical properties. These results revealed that C1N1T exhibited higher surface area, better pore volume and enhanced optical properties as compared to undoped and Ni-doped TiO2. Furthermore, the photoactivity of C1N1T nanoparticles was manifested toward Acetaminophen, Phenol and reactive dyes i.e., Remazol Black B and Yellow 2 G. Moreover, C1N1T nanoparticles showed remarkable degradation efficiency of 53%, 56%, 98% and 89% for Acetaminophen, Phenol and anionic dyes, i.e. Remazol Black B and Yellow 2 G under optimized conditions (pollutant concentration = 20 ppm; time = 120 min; C1N1T loading = 20 mg; irradiation source = solar light; pH = 4 for each dye, pH = 7 for phenol and pH = 9 for acetaminophen). The significant degradation values suggested that the C1N1T photocatalyst can be effectively employed to degrade the textile dyes and PPCPs from industrial wastewater.

Synthesis and characterizations of Ni-SnO2-TiO2 nanocomposite for photocatalytic application

A first attempt was made to synthesize a Ni-SnO2-TiO2 nanocomposite by a one-pot simple synthetic method. A [Ni(im)6]Cl2 precursor complex is preferably adsorbed on the solid surface forming nanocomposite: complex adduct, it simultaneously becomes a surface species (Ni-SnO2-TiO2). In this investigation, it has been found that surface interaction of nickel complex ions lead to the formation of surface species that are identified by XRD, FTIR, UV–vis DRS, SEM, EDX, HRTEM, XPS, and XANES analyses. The metal-loaded metal oxide coupled semiconductor solids find their applications as catalysts and in advanced electronics. We demonstrate the dopant induced changes in electronic density of states using DFT VASP calculations. The photocatalytic property of Ni-SnO2-TiO2 sample was tested, and the results showed that a small amount of nickel surface co-doped SnO2-TiO2, formed an anatase–rutile-cassiterite mixed phases with surface defects or oxygen vacancies, and had improved the photocatalytic activity. The organic model pollutant of Azo dye and methyl orange degradation property of TiO2 photocatalyst under visible light irradiation has greatly enhanced after the introduction of Ni into the SnO2-TiO2 surface matrix. This study points out a potential way to develop new and more active tin and nickel co-doped titania photocatalysts for organic pollutant degradation in water systems.

Hydrothermal route to (Fe, N) codoped titania photocatalysts with increased visible light activity

Hydrothermal route to (Fe, N) codoped titania photocatalysts with increased visible light activity

Visible-light active mesoporous, nanocrystalline N,S-doped and co-doped titania photocatalysts synthesized by non-hydrolytic sol-gel route

Visible-light active mesoporous N,S-doped and co-doped anatase TiO2 powders were synthesized by non-hydrolytic sol-gel route, starting from TiCl4 and Ti(OiPr)4 dissolved in cyclohexane or dimethyl sulfoxide, later used as a S-doping agent. After drying in an inert atmosphere, the gels were annealed at 500°C for 3h, in air or ammonia flow, later used for N-doping. The undoped titania powder, obtained by annealing in air of the cyclohexane-based gel, was also annealed in ammonia to deduce which method is more efficient for N-doping: gel or powder annealing. The post-annealing in air after annealing in ammonia was optimized to attain the best photocatalytic activity for dye degradation under simulated visible light. The size of anatase nanocrystals decreased by doping and the specific surface area of the powders increased. The XPS analysis confirmed a successful substitution of Ti4+ by S(4+) and/or S(6+), which caused a very small band-gap narrowing. The gel annealing in ammonia was much more efficient for interstitial nitrogen incorporation in TiO2 lattice than the powder annealing. The annealing in ammonia of the gel synthesized with dimethyl sulfoxide provided the highest visible-light activity owing to high specific surface area, appropriate mesoporosity and high photoabsorption due to efficient N,S co-doping.

Enhanced photocatalytic hydrogen production from water–methanol mixture using cerium and nonmetals (B/C/N/S) co-doped titanium dioxide

In the present study, photocatalytic hydrogen production from water/methanol solution was investigated over cerium and nonmetal (B/C/N/S) co-doped titanium dioxide catalyst under visible light irradiation. The cerium and nonmetal co-doped titania photocatalysts were prepared by co-precipitation and characterized by surface area and pore size analysis, X-ray diffraction analysis, diffuse reflectance UV–Vis spectroscopy analysis, and photoluminescence analysis. The UV–Visible spectra showed that incorporation of cerium and nonmetals to TiO2 resulted in narrow band gap and improved absorption of visible light. The band gap energy of co-doped samples depended on the properties of nonmetals. Photoluminescence studies showed that the radiative recombination rates of photogenerated electron–hole pairs were effectively suppressed by the addition of cerium and nonmetals and contributed to higher activity. The highest hydrogen production of 206 μmol/h was obtained for Ce–N–TiO2 sample, which can be attributed to the higher surface area, higher absorption of visible light, and higher separation efficiency of electron–hole pairs in Ce–N–TiO2.

Characterization and activity of visible light–driven TiO2 photocatalysts co-doped with nitrogen and lanthanum

Nitrogen and lanthanum co-doped titania photocatalysts were prepared by a modified sol–gel process with urea and lanthanum nitrate doping precursors and characterized by various techniques including XRD, FTIR, TEM, EDS, and UV–Vis DRS. The average crystallite size was ca. 12–15 nm as calculated from XRD patterns, and anatase was the dominant crystalline type in the as-prepared samples. The UV–Vis DRS of the samples revealed significant absorption within the range of 400–500 nm. The optimum composition of N(0.020)La(0.012)TiO2 exhibited the highest photocatalytic activity for degradation of methyl orange (MO) aqueous solution under simulated sunlight. The percent degradation of MO was ca. 97% for N(0.020)La(0.012)TiO2 under simulated sunlight irradiation for 9 h. The enhanced photocatalytic activity was ascribed to the synergistic effects of the nitrogen and lanthanum co-doping.

A mesoporous WN co-doped titania nanomaterial with enhanced photocatalytic aqueous nitrate removal activity under visible light

This manuscript deals with the increased and selective nitrate reduction under visible light over a WN co-doped titania photocatalyst. A series of WN co-doped titania nanomaterials were synthesized with varying tungsten content and were characterized by TEM, XRD, UV-vis and nitrogen adsorption–desorption studies. Tungsten doped materials are found to be noodle shaped and mesoporous with a stable anatase phase after 500 °C calcination. Peak shifting in the XRD pattern indicates the tungsten doping in the crystal lattice. Visible light absorption increases with the increasing tungsten amount. Among the studied hole scavengers, formic acid was found to be the best for nitrate reduction with more than 94% nitrogen gas selectivity. The amount of hole scavenger also controls the reaction efficiency and product selectivity. Both nitrate reduction and nitrogen gas selectivity increases with WN co-doping in comparison to only N doped titania. High nitrate reduction with formic acid is attributed to the formation of CO2˙− species having high reduction potential. The material with 2% tungsten shows the highest surface area and the best photocatalytic activity under visible light. Presence of anion like chloride increases the nitrate photoreduction. Overall high nitrate reduction can be attributed to the synergistic effect of tungsten and nitrogen co-doping, optimum surface hydroxyl group, mesoporosity and appreciable visible light absorption of the materials.

Phosphorus and nitrogen co-doped titania photocatalysts with a hierarchical meso-/macroporous structure

Visible light-active phosphorus and nitrogen co-doped meso-/macroporous titania materials were prepared by a simple two-step approach of the direct phosphation with the use of phosphoric acid solution and the succedent nitridation with the use of the urea solution. The prepared materials were characterized by UV–vis, solid-state 31P MAS NMR, FT-IR, XPS, XRD, SEM, TEM, and N2 adsorption analysis. Direct synthesis of phosphorus-doped meso-/macroporous titania materials could inhibit the formation of brookite phase and increase the surface area significantly, resulting in the hierarchical porous framework of nanocrystalline anatase phase with enhanced thermal stability and large porosity, and these features retained during the subsequent nitridation. The incorporation of P and N in the anatase titania lattice in the form of O–Ti–N, O–P–N, and Ti–O–P linkages was evidenced, and the extension of the absorption edges into the visible region and the corresponding narrowing of band gaps were observed in these N and P co-doped meso-/macroporous titanias, giving a higher photocatalytic activity in the degradation of Rhodamine B dye under visible-light irradiation than the samples doped with only N or P. The beneficial effect of hierarchical meso-/macroporous structure is also examined.

Degradation of nitrobenzene using titania photocatalyst co-doped with nitrogen and cerium under visible light illumination

A type of nitrogen and cerium co-doped titania photocatalyst, which could degrade nitrobenzene under visible light irradiation, was prepared by the sol–gel route. Titanium isopropoxide, ammonium nitrate, and cerium nitrate were used as the sources of titanium, nitrogen, and cerium, respectively. X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV–vis diffusive reflectance spectroscopy (DRS), scanning electron microscopy (SEM), and N 2 adsorption–desorption isotherm were employed to characterize the as-prepared photocatalyst. The degradation of nitrobenzene under visible light illumination was taken as probe reaction to evaluate the photoactivity of the co-doped photocatalyst. The commercial TiO 2 photocatalyst (Degussa P25), which was thought as a high active photocatalyst, was chosen as standard photocatalyst to contrast the photoactivity of the nitrogen and cerium co-doped titania photocatalyst. The results showed that the photocatalytic performance of the nitrogen and cerium co-doped titania was related with the calcination temperature and the component. The nitrogen atoms were incorporated into the crystal of titania and could narrow the band gap energy. The doping cerium atoms existed in the forms of Ce 2O 3 and dispersed on the surface of TiO 2. The improvement of the photocatalytic activity was ascribed to the synergistic effects of the nitrogen and cerium co-doping.

Visible-light-driven titania photocatalyst co-doped with nitrogen and ferrum

Nitrogen and ferrum co-doped titania photocatalyst was prepared by the sol–gel route. The prepared photocatalyst was characterized by various techniques including X-ray diffraction (XRD), UV–vis diffusive reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS), and N 2 adsorption–desorption isotherm. The photocatalytic activity of the co-doped titania photocatalyst was evaluated by the degradation of methyl orange (MO) from aqueous solution under visible light irradiation and was compared with that of the commercial TiO 2 photocatalyst (Degussa P25). The results revealed that the nitrogen doping could lead to the response to visible light and that the ferrum doping could improve the photocatalytic performance. The effects of the component and the annealing temperature of the co-doped titania photocatalyst on the photocatalytic activity were investigated.

Preparation and characterization of visible-light-driven titania photocatalyst co-doped with boron and nitrogen

In order to improve the photocatalytic performance of titania under visible light, a boron and nitrogen co-doped titania photocatalyst was prepared. Its photoabsorbance was measured by UV–vis diffusive reflectance spectroscopy (DRS). The microstructure of photocatalyst was characterized using X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), and scanning electron microscopy (SEM). The microcrystal of the co-doped photocatalyst consisted of anatase phase and was approximately present in the form of spherical particle. The particle size was in correlation with the calcination temperature. Degradation of phenol under visible light illumination was used to evaluate the photocatalytic performance. The calcination temperature and the component influenced the photoactivity. The results showed that the co-doping of boron and nitrogen played an important role in the band gap decrease, which led to the rise of the photocatalytic activity.

Characterization of nitrogen and fluorine co-doped titania photocatalyst: Effect of temperature on microstructure and surface activity properties

Nitrogen and fluorine co-doped titania photocatalyst samples to be used for air purification were prepared by spray pyrolysis using a mixed solution of TiCl 4 and NH 4F. Droplets of the mixed solution formed by nebulizer passed through a ceramic tube furnace under a suction of an aspirator and a titania-based powder was formed at temperatures in the range from 700 to 1000 °C. The resulting nanopowders were characterized by electron microscopy, X-ray diffraction, temperature programmed desorption of NH 3, methods of thermal analysis, particle size, surface area and porosity determination by nitrogen adsorption. Morphology and surface activity of the samples prepared at various conditions were compared. The thermal behavior of the samples characterized by TG, DTA and ETA under air heating conditions is discussed considering the differences in samples preparation. A high photocatalytic activity for acetaldehyde decomposition in a visible region of spectrum depended on the spray pyrolysis temperature and can be ascribed to a synergetic effect of nitrogen and fluorine doping.

Visible-light induced photocatalytic activity of TiO 2− xA y (A = N, S) prepared by precipitation route

Nitrogen doped or nitrogen/sulfur co-doped titania photocatalyst TiO 2− x A y (A = N, S) which can be excited by visible light were prepared by mixing aqueous TiCl 3 solutions with various nitrogen sources such as hydroxylamine (NH 2OH), hexamethylenetetramine (HMT, C 6H 12N 4), urea ((NH 2) 2CO) and thiourea ((NH 2) 2CS) followed by hydrothermal treatment at 190 °C. The titania powders prepared using hydroxylamine consisted of rutile crystals with non-homogeneous size distribution. The nitrogen doped titania powders prepared using hexamethylenetetramine consisted of mainly mono-size spherical brookite crystals, whereas those using urea and thiourea consisted of belt-like rutile particles. The TiO 2− x A y (A = N, S) powders showed excellent visible-light absorption and photocatalytic ability for the oxidative destruction of nitrogen monoxide under irradiation of visible light. The effect of reaction solvents on the phase composition, specific surface area and photocatalytic activity was also characterized.