Commercial Degussa P25 Research Articles

Hydrothermal synthesis of TiO 2 /reduced graphene oxide nanocomposite with enhanced photocatalytic activity

The composite of peanut-like TiO2 nanoparticles and reduced graphene oxide (rGO) was successfully synthesised via a facile one-step hydrothermal method in mixed solvents of diethanol amine and distilled water. The crystallite, morphology and structure features of the composite were characterised by X-ray diffraction, Brunauer-Emmett-Teller specific area analysis, transmission electron microscopy and high-resolution transmission electron microscopy. The results indicated that the as-synthesised TiO2 was of peanut-like shape with about 21–32 nm in length and was anchored on the surface of the rGO sheet. In addition, the TiO2/rGO composite presented excellent photocatalytic activity of rhodamine B under visible light irradiation compared with commercial Degussa P25. A proposed mechanism for the photocatalytic process is also discussed.

Mercury Removal from Flue Gas with Fe-Doped Titania Photocatalyst

The titanium-based nanocatalysts were prepared and used to photocatalytically oxidize Hg0 to remove it in the simulated flue gas in this paper .The modified commercial degussa P25 and Fe3+ doped TiO2 photocatalyst prepared with sol-gel method were applied to conduct the experimenent on self-built experimental platform to test their photocatalytically oxidation performance on mercury in the simulated flue gas.By designing different ratios of Fe2O3/TiO2, comparison experiments under UV(ultra violet) irradiation, it was compared with the result of the experiment and reference documents to verify the rationality of the experimental results and the accuracy. The best catalyst modification conditions were determined and analyzed the Fe-doped TiO2 photocatalytic mechanism to guarantee high or higher mercury removal from flue gas.

Correlating the photocatalytic activity and the optical properties of LiVMoO6 photocatalyst under the UV and the visible region of the solar radiation spectrum

This study presents a simplified method for the evaluation of the optical properties of photocatalytic powders and in particular LiVMoO6, including the extinction (β), absorption (κ) and scattering (σ) coefficients. The optical properties of LiVMoO6 were determined by applying the six-flux radiation absorption–scattering model applied to a photocell geometry and through simple spectrophotometric measurements of diffuse reflectance, diffuse transmittance and collimated transmittance of aqueous suspensions of LiVMoO6. Once the optical properties were determined, the spatial distribution of the local volumetric rate of photon absorption (LVRPA) in an experimental reactor was calculated for the two cases when either ultraviolet light or visible light was used. X-ray diffraction and Raman spectroscopy of the LiVMoO6 resulted in a brannerite type structure of the catalyst. The optimum conditions and catalyst concentration for the degradation and mineralization of a model water contaminant in aqueous suspensions of LiVMoO6, under either UV or visible light irradiation in the experimental reactor, were predicted from the calculated optical properties and by applying the six-flux radiation absorption–scattering model. The photoactivity of LiVMoO6 was compared with that of commercial anatase TiO2 Degussa P25. The highest percentage of organic removal and mineralization was obtained when LiVMoO6 was irradiated with visible light.

Low-temperature stabilization of electrosynthesized tetragonal zirconia, its photoactivity toward methylene blue decolorization

Zirconia nanoparticles (ZrO2) were prepared by a simple electrochemical method and characterized using X-ray diffraction, transmission electron microscopy, Brunnauer–Emmett–Teller surface area analysis, and ultraviolet-visible diffuse reflectance spectroscopy. In this study, tetragonal ZrO2 (t-ZrO2) particles were stabilized at a lower calcination temperature without the addition of a dopant in the preparation step. It was suggested that the use of tetraethylammonium perchlorate as the supporting electrolyte was responsible for the stabilization of t-ZrO2 by preventing the agglomeration of metal clusters with undesired powders in the electrolysis system, resulting in a decrease in ZrO2 crystal size. The photoactivity of the catalyst was optimized using central composite design with response surface methodology and the optimum values of the parameters were a solution pH of 11, contact time of 4 h, catalyst dosage of 1.0 g L−1, and calcination temperature of 523 K. This resulted in 84.9% decolorization of methylene blue (MB) obtained from the predicted model, which fitted well with the laboratory results of 83.6%. The kinetics study demonstrates that the reaction followed pseudo first-order kinetics, and the rate constants KR = 0.09 mg L−1 h−1 and KLH = 0.43 L mg−1 were determined using the Langmuir–Hinshelwood model. The mineralization of MB was measured by chemical oxygen demand removal, BOD5/COD, and TOC/TOC0 ratio analyses with values of 78.5%, 1.48, and 0.21, respectively, after 4 h of contact time. The regeneration study shows that the catalyst could be maintained with a slight decrease in decolorization (<10%) after five cycling runs. Furthermore, t-ZrO2 facilitated good photoactivity towards MB decolorization under UV light in a batch reactor compared with commercial t-ZrO2 (58.7%) and Degussa P25 TiO2 (64.5%).

Green synthesis of anatase TiO(2) nanocrystals with diverse shapes and their exposed facets-dependent photoredox activity.

The exposed facets of a crystal are known to be one of the key factors to its physical, chemical and electronic properties. Herein, we demonstrate the role of amines on the controlled synthesis of TiO2 nanocrystals (NCs) with diverse shapes and different exposed facets. The chemical, physical and electronic properties of the as-synthesized TiO2 NCs were evaluated and their photoredox activity was tested. It was found that the intrinsic photoredox activity of TiO2 NCs can be enhanced by controlling the chemical environment of the surface, i.e.; through morphology evolution. In particular, the rod shape TiO2 NCs with ∼25% of {101} and ∼75% of {100}/{010} exposed facets show 3.7 and 3.1 times higher photocatalytic activity than that of commercial Degussa P25 TiO2 toward the degradation of methyl orange and methylene blue, respectively. The higher activity of the rod shape TiO2 NCs is ascribed to the facetsphilic nature of the photogenerated carriers within the NCs. The photocatalytic activity of TiO2 NCs are found to be in the order of {101}+{100}/{010} (nanorods) > {101}+{001}+{100}/{010} (nanocuboids and nanocapsules) > {101} (nanoellipsoids) > {001} (nanosheets) providing the direct evidence of exposed facets-depended photocatalytic activity.

Controlled synthesis and photocatalytic properties of Ag3PO4 microcrystals

Silver phosphates (Ag3PO4) with varied morphology were prepared via an ammonia-mediate method. The as-prepared Ag3PO4 has a cubic-type structure and the morphologies are controlled under different ratio of water and ethylene glycol. The decomposition test of RhB indicated that the uniform morphology of Ag3PO4 exhibit much higher photocatalytic activities than that of not uniform ones under visible light irradiation. The DeNOx experiments revealed that the micronsize Ag3PO4 microcrystals possessed photocatalytic ability lower than that of the commercial Degussa P25 under ultraviolet and visible light irradiation, which suggested that the size of Ag3PO4 is a key role for DeNOx.

Large-scale synthesis of TiO2 microspheres with hierarchical nanostructure for highly efficient photodriven reduction of CO2 to CH4.

In this study, a simple and reproducible synthesis strategy was employed to fabricate TiO2 microspheres with hierarchical nanostructure. The microspheres are macroscopic in the bulk particle size (several hundreds to more than 1000 μm), but they are actually composed of P25 nanoparticles as the building units. Although it is simple in the assembly of P25 nanoparticles, the structure of the as-prepared TiO2 microspheres becomes unique because a hierarchical porosity composed of macropores, larger mesopores (ca. 12.4 nm), and smaller mesopores (ca. 2.3 nm) has been developed. The interconnected macropores and larger mesopores can be utilized as fast paths for mass transport. In addition, this hierarchical nanostructure may also contribute to some extent to the enhanced photocatalytic activity due to increased multilight reflection/scattering. Compared with the state-of-the-art photocatalyst, commercial Degussa P25 TiO2, the as-prepared TiO2 microsphere catalyst has demonstrated significant enhancement in photodriven conversion of CO2 into the end product CH4. Further enhancement in photodriven conversion of CO2 into CH4 can be easily achieved by the incorporation of metals such as Pt. The preliminary experiments with Pt loading reveal that there is still much potential for considerable improvement in TiO2 microsphere based photocatalysts. Most interestingly and significantly, the synthesis strategy is simple and large quantity of TiO2 microspheres (i.e., several hundred grams) can be easily prepared at one time in the lab, which makes large-scale industrial synthesis of TiO2 microspheres feasible and less expensive.

Application of microcrystalline cellulose to fabricate ZnO with enhanced photocatalytic activity

Microcrystalline cellulose (MCC), deriving from naturally renewable biomass resources, has been used to fabricate nanocrystalline ZnO materials via a facile hydrothermal method. XRD analysis results indicate that the obtained ZnO crystallite possess hexagonal wurtzite structure. Its morphology was measured by SEM, showing slice clusters and flowers. Comparatively, ZnO of irregular slices was prepared when no MCC was added in the synthetic route. ZnO synthesized with and without MCC behaves quite different photocatalytic activity. It is found that photocatalytic efficiency of ZnO prepared by 1g MCC on degrading methylene blue reaches 98.3% under UV irradiation (power of 6W). This is higher than the catalytic efficiency of both the ZnO prepared without MCC addition and of the commercial Degussa P25. Simultaneously, the as-prepared ZnO also exhibits excellent reusable ability. No obvious abatement is observed after the catalyst is re-used for 5 cycles. Taken together high photocatalytic and re-used efficiency, we anticipate that our controllable, environment-friendly and cost-effective approach can be applied to synthesize ZnO catalytic materials on a large scale.

Template-free fabrication of rattle-type TiO2hollow microspheres with superior photocatalytic performance

In the paper, an environmentally friendly and template-free route based on a simple hydrothermal process has been developed for preparing rattle-type TiO2 hollow microspheres by using titanium(IV) sulfate (Ti(SO4)2) as the titanium source and glycerol/water as the cosolvent. The SEM and TEM images showed that the obtained TiO2 products were rattle-type hollow nanostructures with a diameter of ca. 1.1 μm. More importantly, the products have a good thermal stability and high crystallinity, which is favorable for their practical applications. According to the experimental results, a possible formation mechanism involving the Ostwald ripening process was proposed combined with various techniques such as SEM, TEM, BET, IR, and UV-vis. The photocatalytic results indicated that the TiO2 microspheres obtained from 750 °C thermal treatment exhibited higher photocatalytic activity for the photodegradation of methyl orange (MO) than those of other calcination temperatures and commercial Degussa P25. To further improve the photocatalytic activity, Ag-doped TiO2 photocatalyst was also prepared by the impregnation method. The results indicated that the photocatalytic activity of the Ag/TiO2 catalysts was greatly enhanced compared with the pure TiO2 catalysts. The possible photodegradation mechanism was also discussed.

Efficient ZnO-based visible-light-driven photocatalyst for antibacterial applications.

Herein, we report the development of a ZnO-based visible-light-driven photocatalyst by interfacial charge transfer process for the inactivation of pathogens under visible-light illumination. Surface modification by a cocatalyst on ZnO, prepared by flame spray pyrolysis process is carried out to induce the visible-light absorption in ZnO. Optical studies showed that surface modification of Cu(2+) induces the visible-light absorption in ZnO by interfacial charge transfer between ZnO and surface Cu(2+) ions upon light irradiation. The photocatalytic efficiency of pure and modified ZnO is evaluated for the inactivation of pathogens and the decomposition of methylene blue under visible-light illumination. The antibacterial activity of Cu(2+)-ZnO is several orders higher than pure ZnO and commercial Degussa-P25 and comparable with Cu(2+)-TiO2. Cu(2+)-ZnO nanorods show better photocatalytic activity than Cu(2+)-ZnO nanosphere, which is attributed to high surface area to volume ratio of former than later. The holes generated in the valence band and the Cu(1+) species generated during the interfacial charge transfer process may attribute for the inactivation of bacteria, whereas the strong oxidation power of hole is responsible for the decomposition of methylene blue. Besides the advantage of Cu(2+)-modified ZnO for visible-light-assisted photocatalytic applications, the method (FSP) used for the synthesis of ZnO in the present study is attractive for commercial application because the process has potential for the production of large quantities (2-3 kg/h) of semiconductors.

A novel route for the production of TiO2 photocatalysts with low energy gap, via Triton-X and oleic acid surfactants

Mesoporous anatase TiO2 photocatalysts with high specific surface area between 70 and 110m2/g were prepared via a novel sol–gel technique using surfactants oleic acid and Triton-X in the presence or absence of diethanolamine. Titania materials showed increased photocatalytic performance in UV light. The production of active species seem to be high enough to perform the degradation of methylene blue dye solution in low catalyst concentration; and a relatively high efficiency in NO oxidation in gaseous phase. All materials prepared showed high photocatalytic activity and degradation efficiency similar or higher compared to commercial Degussa P25 material.

Low-Temperature Nitrogen Doping in Ammonia Solution for Production of N-Doped TiO2-Hybridized Graphene as a Highly Efficient Photocatalyst for Water Treatment

To facilitate the potential application of TiO2 as an efficient photocatalyst, the modulation of its band gap and electrical structure is of great significance. Herein, we report a very simple nitrogen (N)-doping method to obtain N-doped TiO2, which is hybridized with graphene sheets at a temperature as low as 180 °C and using an ammonia solution as the N source and reaction medium. X-ray photoelectron spectroscopy analysis revealed that the atomic N level could reach 2.4 atomic percent when the reaction time was 14 h. Photoluminescence (PL) emission spectra indicated that N-doped TiO2/graphene composites have drastically suppressed TiO2 PL intensity when compared to undoped TiO2, confirming the lower recombination rate of electron–hole pairs in the N-doped TiO2. Additionally, photodegradation data showed that the decomposition rate of methylene blue with our N-doped TiO2/graphene photocatalyst is twice as fast as a commercial Degussa P25 catalyst. Furthermore, density functional theory (DFT) calculations demonstrate that N doping creates empty states in the band gap of the TiO2 that are below the Fermi energy of graphene. Thus, when N-doped TiO2 is brought into contact with graphene, these states become filled by electrons from the graphene, shifting the TiO2 bands upward relative to the graphene. Such a shift in band alignment across the TiO2/graphene heterojunction makes transfer of the photoexcited electron more energetically favorable. This work provides a very convenient chemical route to the scalable production of N-doped TiO2/graphene photocatalyst for potential applications in wastewater treatment.

Photoreduction of toxic chromium using TiO2-immobilized under natural sunlight: effects of some hole scavengers and process parameters

This work focuses on the photocatalytic reduction of Cr(VI)–Cr(III) using TiO2-immobilized onto glass slides under natural sunlight. The commercial TiO2 Degussa P25 was used as a photocatalyst in this work. The effects of some additives as hole scavengers for Cr(VI) reduction are studied. The results show that their presence enhances the reduction rate in the order: tartaric acid > oxalic acid > EDTA > ethanol > methanol > no-additive. The optimization of tartaric acid concentration is determined. The effect of process parameters such as Cr(VI) concentration, pH, and the presence of interfering substances such as inorganic anions (SO42-, CO32-, NO3-, Cl- and PO43-) and metallic cations (Fe3+, Cu2+, Zn2+, and Mn2+) is investigated. The results show that the removal rate is maximum at pH 1.5. On the other hand, the coexistence of interfering ions with Cr(VI) decreases the reduction rate except for the Fe3+. Finally, the results show that the TiO2-immobilized can be reused several times.

Nanoscale anatase TiO2 with dominant {111} facets shows high photocatalytic activity

Abstract In this work, we report a novel synthesis of nanoscale anatase TiO 2 with dominant highly active {1 1 1} facets by a simple one-step hydrothermal route with the assistance of NH 4 F and HF. In this progress, the exposed crystal facets of TiO 2 can been directly tuned by controlling the mole ratio of NH 4 + and F − . When the mole ratio of NH 4 + and F − reach 1:2, nanoscale anatase TiO 2 with dominant {1 1 1} facets can be obtained. Nanoscale anatase TiO 2 with exposed {1 0 1} or {0 0 1} facets will be prepared when there is only ammonia or HF added respectively. Such nano-TiO 2 with exposed highly active {1 1 1} facets has large specific surface area and shows excellent photocatalytic activity: as much as 2–3 times than that of TiO 2 nanosheets with exposed {0 0 1} facets and commercial Degussa P25 which confirms the {1 1 1} facets have higher photocatalytic activity than {0 0 1} and {1 0 1} facets. The higher photocatalytic activity of {1 1 1} facets can be ascribed to the fact that all Ti and O atoms on the surface are unsaturated Ti 5c , Ti 3c and O 2c modes which produces a higher adsorption and degradation ability. The present work demonstrates a explore of hydrothermal synthetic method for controlling preparation of nano-materials.

Antimicrobial potential of TiO2 nanoparticles against MDR Pseudomonas aeruginosa

The present study aims to evaluate the inhibition effectiveness of titanium dioxide nanoparticles in combination with cell wall active antibiotics – ceftazidime and cefotaxime against the multi-drug resistant Pseudomonas aeroginosa isolated from pus, sputum, endo-tracheal tract and broncho-alveolar lavage. Commercial Degussa-P25 TiO2 nanoparticle, antibiotics ceftazidime and cefotaxime were used in this study against multi-drug-resistant nosocomial pathogen. The nanoparticle shows antimicrobial effect on the pathogen at concentrations more than 350 μg/mL, when exposed to ultraviolet (UV) light for an hour. Minimum inhibitory concentration values obtained for the antibiotic cefotaxime were sixfolds higher than the antibiotic ceftazidime. When these antibiotics were used in combination with UV-irradiated metal nanoparticle, ceftazidime resulted in enhanced antimicrobial activity whereas cefotaxime does not show any change.

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–TiO2−xNx) 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–TiO2−xNx. 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–TiO2−xNx 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–TiO2−xNx and commercial Degussa P25 was determined. The higher visible light activity of Ce–TiO2−xNx was due to the participation of MMCT and interfacial charge transfer mechanism.

Sol–gel Mediated Coating and Characterization of Photocatalytic Sand and Fumed Silica for Environmental Remediation

This paper reports about the modification of sand and fumed silica with titania in order to obtain a photocatalytic active material for the degradation of pollutants. The coating process was performed based on the sol–gel method. Tetrapropylorthotitanate was used as the titania precursor to apply a nanoscaled layer on sand grains. For silica fume, the coating process was varied. Various amounts of tetrapropylorthotitanate were used to obtain different coating thicknesses and to identify the maximum amount of titania that could be loaded on the material. All samples showed high photonic efficiencies in the degradation of nitrogen monoxide despite their low titania quantities, which were identified via x-ray fluorescence analysis. Some samples showed higher photonic efficiencies than commercial Degussa P25. Due to the preparation method, calcination of the sand composites was not necessary to yield a crystalline coating which was responsible for the high photocatalytic activity. However, silica fume composites had to be calcined possibly due to variation in the preparation method. Scanning electron micrographs revealed the structured morphology of all specimens. Energy dispersive x-ray analysis identified nanoscaled titania particles on the sand surface that could not be observed only via SEM. The results of this research are especially interesting for large scale applications of photocatalysts. As industrial sand and silica fume used are low cost materials, this new kind of photocatalyst can be applied in higher quantities and distributed onto larger areas, while saving costs at the same time.

Biogenic C-doped titania templated by cyanobacteria for visible-light photocatalytic degradation of Rhodamine B

Cyanobacteria, which occurred in eutrophic water harvest solar light to carry out photosynthesis with high efficiency. In this work, cyanobacteria (Microcystis sp.) were used as biotemplate to synthesize titania structure. The synthesized titania sample had similar morphology to that of the original template in spite of the fragile unicellular structures and extremely high water content of cyanobacterial cells. Incorporation of biogenic C, as well as the morphology inherited from biotemplate improved visible-light absorbance of the titania structure. The sample exhibited higher visible-light photocatalytic activity than commercial titania photocatalyst Degussa P25 for Rhodamine B (RhB) degradation. Compared with those C-doped titania photocatalysts prepared by other methods, cyanobacteria templated titania photocatalyst offer some potential for competitive advantages. The reported strategy opened up a new use for the cyanobacteria. It could also be used for titania in applications such as treatment of polluted water, dye-sensitized solar cells, or other regions.

Effects of TiO2 nanostructure and operating parameters on optimized water disinfection processes: A comparative study

Abstract This paper reports the performance of bacterial disinfection using 3D dendritic titanium dioxide with nanoribbon structures (3DD-TiO2), which is newly developed by the researchers. Characterization of 3DD-TiO2 using SEM and TEM shows that the diameter of nanoribbons is nearly 18 nm only, resulting in an aspect ratio of more than 50. The hierarchical porous structure of the 3DD-TiO2 would greatly favor the improvement of photocatalytic activity via enlarging the specific surface area. In comparison with the same-sized microspheres and commercial Degussa P25, which are both spherically structured, 3DD-TiO2 displays a consistently better performance under the tested environment. Without UV illumination, the removal efficiency of Escherichia coli by 3DD-TiO2 is 6.4% and 8.7% higher than that of microspheres and P25, respectively. Under UV radiation, the disinfection kinetic constant k of the disinfection reaction using 3DD-TiO2 is 23.2% and 33.9% higher than that of using microspheres and P25, respectively. A series of optimization studies have been carried out to identify the optimum operating parameters of a photocatalytic process using 3DD-TiO2. The results tend to suggest: (a) optimum catalyst concentration is around 100 mg/L; (b) the optimum temperature for bacteria inactivation ranges between 10 °C and 20 °C; (c) presence of humic acid and anions (SO42−) exhibits an inhibitory effect on water disinfection process; and (d) cations (Ca2+) enhance the disinfection rate. These optimum operating parameters could be directly referenced for full-scale applications in future.

Cetyltrimethylammonium Bromide-Assisted Hydrothermal Synthesis of Mixed-Phase TiO&lt;sub&gt;2&lt;/sub&gt; Nanorod and its Photocatalytic Activity

TiO2nanorods were successfully fabricated via hydrothermal method using cetyltrimethylammonium bromide (CTAB) as the structure-directing agent. The synthesized samples were investigated by X-ray diffraction (XRD), transmission electron microscopy (TEM), and field-emission scanning electron microscope (FESEM). The study showed that as-prepared samples were the mixed crystalline phase of rutile and brookite. The weight fraction of rutile and brookite in the mixed-phase were accurately tuned by changing the concentration of CTAB. The morphology of prepared samples was TiO2nanorods with the diameter of 2530 nm and the length of 80150 nm. The samples for degradation of papermaking wastewater under ultraviolet light irradiation showed better photocatalytic activity than the commercial Degussa P25. HRT-3 prepared from CTAB: TBT molar ratio of 0.48 exhibited the highest photocatalytic activity, achieving 47.2% CODcrremoval rate and 89.5% chroma removal rate under irradiation 12 h.