The Effect of Iron and Niobium Co-Doping Ratio on the Photocatalytic Activity of Sol-Gel Derived Titanium Dioxide (original) (raw)
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Enhanced photocatalytic activity and stability of nano-scaled TiO2 co-doped with N and Fe
Applied Surface Science, 2011
Titanium dioxide (TiO 2 ) nanoparticles co-doped with N and Fe were prepared via modified sol-gel process. The products were characterized by transmission electron microscopy (TEM), N 2 adsorption, X-ray diffraction (XRD), Raman spectroscopy, UV-vis spectroscopy, photoluminescence (PL), and X-ray photoelectron spectroscopy (XPS). It is shown that the prepared TiO 2 particles were less than 10 nm with narrow particle size distribution. The addition of MCM-41 caused the formation of Ti-O-Si bond which fixed the TiO 2 on MCM-41 surface, thus restricted the agglomeration and growth of TiO 2 particles. The photocatalytic performance in the degradation of methylene blue showed that N, Fe co-doped TiO 2 exhibited much higher photocatalytic activity than doped sample with nitrogen or Fe 3+ alone under both UV and visible light. N, Fe co-doping decreased the loss of doping N during the degradation reaction, thus increased the photocatalytic stability. It was also found that the nitridation time had significant influence on the photocatalytic activity of prepared TiO 2 catalysts.
Enhanced photocatalytic activity of TiO2 assisted by Nb, N and S multidopants
Materials Research Bulletin, 2015
A novel visible light active photocatalyst is synthesized by doping TiO 2 with multiple dopants like Nb, N and S. TiO 2 exists as anatase phase and the particle size is in the range of 10-25 nm. A significant red shift of the absorption edge and increased visible light absorption is shown by multidoped TiO 2 compared to undoped TiO 2 . The tri-doped TiO 2 has the highest activity for the photodegradation of methyl orange and the activity shows the order: 0.6NbNS-TiO 2 > P25 > 0.6Nb-TiO 2 > NS-TiO 2 > pristine TiO 2 . The enhanced photocatalytic activity of tri-doped TiO 2 is due to the reduction of band gap and enhancement of lifetime of photogenerated charge carriers. This multidoped catalyst is found to be stable and only a marginal decrease in the activity is observed upto 3 cycles. Experiments with quenchers suggest that all super oxide, hydroxyl radicals and photogenerated holes are active species for the oxidation reaction.
Composite TiO2-based photocatalyst with enhanced performance
Photochemical & Photobiological Sciences
TiO 2 is the most studied photocatalyst because of its non-toxicity, chemical stability, and low cost. However, the problem of TiO 2 is its low activity in the visible region of the spectrum. In this study, we focused on the preparation of composite photocatalytic materials with altered light absorption properties. TiO 2 P25 and various metal oxides were mechanically joined by ball-milling and immobilized on glass plates. The prepared samples were evaluated based on their ability to degrade NO in gas phase. The formation of undesirable byproducts was also investigated. Four best performing composites were later chosen, characterized, and further evaluated under various conditions. According to their performance, the metal oxide additives can be divided into three groups. P25/Fe 2 O 3 showed the most promising results-an increase in overall deNO x activity under modified ISO conditions and altered selectivity (less NO 2 is formed) under both simulated outdoor and simulated indoor conditions. On the other hand, P25/V 2 O 5 composite showed negligible photocatalytic activity. The intermediate group includes P25/WO 3 and P25/ZnO photocatalysts, whose performances are similar to those of pristine P25.
Journal of Materials Science: Materials in Electronics, 2018
The aim of this work was synthesis and investigation of various properties of Co-doped titanium dioxide nanostructures. Synthesis was conducted by the co-precipitation method using cobalt nitrate and titanium isopropoxide as a precursor, followed by thermal treatment at a temperature of 500 °C. The materials were fully characterized using several techniques (X-ray diffraction XRD, SEM, FTIR, TGA/DTA, UV-Vis diffuse reflectance DRS and photoluminescence). However, dopant has no effect on XRD pattern of the host but it can influence on the various characteristics of host such as optical and electrical properties. The scanning electron microscopy was used to detect the morphology of synthesized nanoparticles which sizes changed with the altitude in the doping concentration to 6%. FTIR spectra exhibit broad peaks where anatase phases of TiO 2 demonstrate very sharp UV-Vis band gap results showed the reduction in band gap from from 3.21 eV, for undoped TiO 2 , to 2.74 eV, for Co doped 6% TiO 2. The photocatalytic activity of the samples were studied based on the degradation of methyl orange as a model compound, where the results showed that Co doped 6% TiO 2 a good photocatalytic activity.
Development of alternative photocatalysts to TiO2: Challenges and opportunities
Energy & Environmental Science, 2009
Since the early development of this technology in the 1970s, TiO 2 constitutes the archetypical photocatalyst due to its relatively high efficiency, low cost and availability. However, during the last decade a considerable number of new photocatalytic materials, either semiconductor or not, have been proposed as potential substitutes of TiO 2 , particularly in the case of solar applications, for which this standard photocatalyst is not very suitable because of its wide band gap. Semiconductors based on cations with d 0 configuration such Ta 5+ or Nb 5+ , as well as oxides or nitrides of d 10 elements such as Bi 3+ , In 3+ or Ga 3+ are among the most successful novel photocatalysts, but non-semiconductor solids like cation-interchanged zeolites also produce interesting results. In addition, some classical semiconductors like ZnO or CdS, initially discarded as a consequence of their poor stability under irradiation, have been reconsidered as feasible photocatalysts for particular applications. This growing body of data requires new analysis of the challenges and opportunities facing photocatalysis in order to assess which of the photoactive materials are best for each particular application. In this review, we summarize, with an historical perspective, the main achievements obtained with photocatalyst alternatives to TiO 2 in the three main niches for this technology: water splitting for hydrogen production, decontamination and disinfection processes, and organic synthesis.
Influence of N sources on the photocatalytic activity of N-doped TiO2
Arabian Journal of Chemistry, 2020
Influence of nitrogen precursors urea, semicarbazide and N,N'-dimethyl urea on the photocatalytic activity of the N-doped TiO 2 were studied by a simple decomposition method. The nano N-TiO 2 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-TiO 2 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 m 2 /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-TiO 2 samples prepared from precursors which can potentially form the melamine and its oligomerized products on the surface of TiO 2 .
Journal of Technology Innovations in Renewable Energy, 2015
Iron-doped TiO2 nanopowders with different doping amounts have been prepared by co-precipitation method followed by heat treatment. The obtained materials were structurally, morphologically and analytically characterized by X-ray diffraction (XRD), FT-Raman spectroscopy, diffuse reflectance spectroscopy (DRS) and energy dispersive X-ray spectroscopy (EDX) coupled to scanning electron microscopy (SEM). XRD analysis revealed the major presence of the anatasa crystalline phase for iron-doped and undoped TiO2. SEM confirmed particles sizes among the nanometer scale along with XRD data. The presence of iron ions was validated by EDX-SEM. Diffuse reflectance techniques were carried out to validate the shift of the band edge absorption spectrum of doped TiO2 nanoparticles towards the visible region and to confirm the presence of iron atoms in the TiO2 crystal lattice by the resulting variation of the band gap value of the doped materials. Photocatalytic activity of the nanoparticles under UV and visible radiation was evaluated by means of hydroxyl radicals production through indirect estimation using N,N-dimethyl-p-nitrosoaniline (PNDA)photo-discoloration experiments in aqueous dispersion. Samples containing 1.2 and 5.6 weight % Fe exhibited the highest activities in this study for both conditions.
Visible-light activation of TiO2 photocatalysts: Advances in theory and
Though there are many advantages for the TiO2 compared to other semiconductor photocatalysts, its band gap of 3.2 eV restrains application to the UV-region of the electromagnetic spectrum ( ≤ 387.5 nm). As a result, development of visible-light active titanium dioxide is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in the strategies for the visible light activation, origin of visible-light activity, and electronic structure of various visible-light active TiO2 photocatalysts are discussed in detail. It has also been shown that if appropriate models are used, the theoretical insights can successfully be employed to develop novel catalysts to enhance the photocatalytic performance in the visible region. Recent developments in theory and experiments in visible-light induced water splitting, degradation of environmental pollutants, water and air purification and antibacterial applications are also reviewed. Various strategies to identify appropriate dopants for improved visible-light absorption and electron–hole separation to enhance the photocatalytic activity are discussed in detail, and a number of recommendations are also presented.
Enhancement of the activity of TiO 2-based photocatalysts : a review
2015
Titania is one of the most widely used standard reference photocatalysts in the field of environmental applications. However, the wide anatase band gap and high degree of recombination between photogenerated charge carriers is limiting titania overall photocatalytic efficiency in water and air purification. This paper reviews recent studies on semiconductor photocatalysis, carried out at the Institute of Catalysis of the Bulgarian Academy of Sciences, aimed at enhancing the efficiency of TiO2-based photocatalysts and obtaining novel photocatalytic systems for sunlight utilization and application of methods improving the overall performance of the photocatalytic processes.
Iron-doped TiO 2 Catalysts with Photocatalytic Activity
The aim of the present study is to synthesize and characterize Fe-doped TiO 2 nanoparticles prepared by a molten salt method using a solid mixture of TiO 2 powder and FeCl 3 precursor. As far as this study is concerned, this is the simplest method that has been reported so far for the synthesis of Fe-doped TiO 2 nanoparticles. Pure TiO 2 nanoparticles and 0.5, 1 and 3 wt% Fe-doped TiO 2 samples were prepared. The prepared nanoparticles were characterized by UV-Vis diffusion reflection spectroscopy (DRS), scanning electron microscopy (SEM), X-ray diffraction (XRD) and Energy-dispersive X-ray spectroscopy (EDX). SEM and XRD analysis of the samples indicated the presence of anatase spherical-shaped TiO 2 particles. The results of EDX study confirmed the presence of Fe in all samples. According to DRS results, the band gap energy of Fe doped TiO 2 nanoparticles decreased with increasing Fe concentration from 3.1 eV for pure TiO 2 to 3.0-2.80 eV for Fe-doped TiO 2. The photocatalytic activity was also checked. It was found that, the photocatalytic activity of Fe-doped nanoparticles was higher than that of the pure TiO 2. The maximum degradation activity of 69% was obtained at the Fe doping content of 0.5 wt%.