- Charge carrier dynamics and photocatalytic behavior of TiO2 nanopowders submitted to hydrothermal or conventional heat treatment
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The sol-gel technique followed by conventional (TiO2-1) and hydrothermal (TiO2-2) thermal treatment was employed to prepare TiO2-based photocatalysts with distinct particle sizes and crystalline structures. The as prepared metal oxides were evaluated as photocatalysts for gaseous HCHO degradation, methanol, and dye oxidation reactions. Additionally, metallic platinum was deposited on the TiO2 surfaces and H2 evolution measurements were performed. The photocatalytic activities were rationalized in terms of morphologic parameters along with the electron/hole dynamics obtained from transient absorption spectroscopy (TAS). TiO2-2 exhibits smaller particle size, poorer crystallinity, and higher surface area than TiO2-1. Moreover the hydrothermal treatment leads to formation of the metastable brookite phase, while TiO2-1 exhibits only the anatase phase. TAS measurements show that the electron/hole recombination of TiO2-2 is faster than that of the latter. Despite that, TiO2-2 exhibits higher photonic efficiencies for photocatalytic oxidation reactions, which is attributed to its larger surface area that compensates for the decrease of the surface charge carrier concentration. For H2 evolution, it was found that the surface area has only a minor effect and the photocatalyst performance is controlled by the efficiency of the electron transfer to the platinum islands. This process is facilitated by the higher crystallinity of TiO2-1, which exhibits higher photonic efficiency for H2 evolution than that observed for TiO2-2. The results found here provide new insights into the correlations between thermal treatment conditions and photocatalytic activity and will be useful for the design of high performance photocatalysts.
- Patrocinio,Schneider,Fran?a,Santos,Caixeta,Machado,Bahnemann
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- Morphology-Engineered Highly Active and Stable Ru/TiO2 Catalysts for Selective CO Methanation
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Ru/TiO2 catalysts exhibit an exceptionally high activity in the selective methanation of CO in CO2- and H2-rich reformates, but suffer from continuous deactivation during reaction. This limitation can be overcome through the fabrication of highly active and non-deactivating Ru/TiO2 catalysts by engineering the morphology of the TiO2 support. Using anatase TiO2 nanocrystals with mainly {001}, {100}, or {101} facets exposed, we show that after an initial activation period Ru/TiO2-{100} and Ru/TiO2-{101} are very stable, while Ru/TiO2-{001} deactivates continuously. Employing different operando/in situ spectroscopies and ex situ characterizations, we show that differences in the catalytic stability are related to differences in the metal–support interactions (MSIs). The stronger MSIs on the defect-rich TiO2-{100} and TiO2-{101} supports stabilize flat Ru nanoparticles, while on TiO2-{001} hemispherical particles develop. The former MSIs also lead to electronic modifications of Ru surface atoms, reflected by the stronger bonding of adsorbed CO on those catalysts than on Ru/TiO2-{001}.
- Chen, Shilong,Abdel-Mageed, Ali M.,Li, Dan,Bansmann, Joachim,Cisneros, Sebastian,Biskupek, Johannes,Huang, Weixin,Behm, R. Jürgen
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- Polyol mediated synthesis of tungsten trioxide and Ti doped tungsten trioxide. Part 1: Synthesis and characterisation of the precursor material
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Polyol mediated synthesis for the preparation of tungsten trioxide and titanium doped tungsten trioxide has been reported. The reaction was carried out using chlorides of tungsten and titanium in diethylene glycol medium and water as the reagent for hydrolysis at 190 °C. Formation of a blue coloured dimensionally stable suspension of the precursor materials was observed during the course of the reaction. The particle sizes of the precursor materials were observed to be around 100 nm. The precursor materials were annealed to give tungsten trioxide and titanium doped tungsten trioxide. The precursor materials were characterised using TGA/DTA, FT-IR, optical spectra, SEM, TEM and powder XRD methods. It was observed that the doping of titanium could be effected at least up to 10% of Ti in WO3. The TGA/DTA studies indicated that WO3-x·H2O is the dominant material that formed during the polyol mediated synthesis. The XRD data of the annealed samples revealed that the crystalline phase could be manipulated by varying the extent of titanium doping in the tungsten trioxide matrix.
- Porkodi,Yegnaraman,Jeyakumar
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- Interplay of Pt and Crystal Facets of TiO2: CO Oxidation Activity and Operando XAS/DRIFTS Studies
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In this work, the influence of the terminating or exposed crystal planes of anatase TiO2 support on the catalytic activity of Pt/TiO2 catalysts is reported. Strong effects were observed when using CO oxidation as a probe reaction. The CO oxidation activity over these catalysts ranks in the following order: Pt/TiO2-{101} > Pt/TiO2-{100} > Pt/TiO2-{001}. The combination of in situ X-ray absorption spectroscopy, X-ray emission spectroscopy, diffuse reflectance infrared Fourier transform spectroscopy, and density functional theory calculations unravelled a strong interaction between platinum particles and different dominating facets of anatase. The catalytic activity of the Pt/TiO2 catalysts can be correlated with the spectroscopic/structural results. Compared to {001} facets, the {100} and {101} facets of TiO2 can stabilize active highly dispersed Pt species and avoid sintering Pt particles. This finding provides some important insights into understanding the metal-support interfacial interactions of Pt/TiO2 catalysts for tuning their catalytic performance. (Graph Presented).
- Zhou, Ying,Doronkin, Dmitry E.,Chen, Menglu,Wei, Shiqian,Grunwaldt, Jan-Dierk
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- Removal of ciprofloxacin from aqueous solution using long TiO2 nanotubes with a high specific surface area
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Long TiO2 nanotubes (TNs) were successfully prepared by the reaction of TiO2 and NaOH. The raw materials were treated by stirring, ion exchange, centrifugation, and freeze-drying, and then the target TNs was synthesized. Anatase TNs were obtained by calcinating the TNs at 823 K for 4.5 h. The TNs were characterized by Brunauer-Emmett-Teller surface area analysis, X-ray diffraction analysis, scanning electron microscopy, transmission electron microscopy, and X-ray photoelectron spectrometry. The results indicated that the TNs had a larger specific surface area (ca. 160 m2 g-1) and pore volume (ca. 0.6 cm3 g-1) than the commercial product P25. The adsorption of ciprofloxacin onto the TNs was compared with their adsorption onto P25. The adsorption isotherm, kinetics, and regeneration performance were investigated. The experimental results indicated that the maximum adsorption capacity of the TNs and P25 was 26.38 and 5.32 mg g-1, respectively, and their adsorption behavior was better fitted by the Langmuir model than by the Freundlich model. The kinetic regression results showed that the adsorption kinetics were more accurately represented by a pseudo-second-order model than by a pseudo-first-order model; the rate of the pseudo-second-order reactions on P25 and the anatase TNs were 0.0442 and 0.27463 min-1, respectively. After adsorption, the TNs had better regeneration properties than P25 under UV irradiation at 500 W for 3 h in 5 mL of aqueous solution. These results show that long TNs have a better adsorption capacity and regeneration properties than P25. This study provides a green method for the removal of organic pollutants by combining enrichment by adsorption with photocatalytic degradation.
- Zheng, Kai,Zheng, Xingye,Yu, Fei,Ma, Jie
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- Effect of electron transfer on the photocatalytic hydrogen evolution efficiency of faceted TiO2/CdSe QDs under visible light
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Quantum dot (QD)/TiO2 composites are widely used materials in the field of photocatalysis. However, the influence of different exposed facets of TiO2 in composites on photocatalytic hydrogen evolution is rarely reported. In this work, CdSe QD-TiO2 composites with dominant {001} or {101} faceted anatase were synthesized and specifically characterized using X-ray powder diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy. Photocatalytic hydrogen evolution tests reveal that {001}-TiO2/CdSe QDs exhibit a 213.1- and 9.0-fold increase in photocatalytic activity compared to {001}-TiO2 and CdSe QDs, respectively. Notably, the photocatalytic activity of {001}-TiO2/CdSe QDs is 2.2 times higher than that of {101}-TiO2/CdSe QDs. Based on the results from UV-Vis diffuse reflectance spectroscopy, Brunauer-Emmett-Teller surface area testing, Mott-Schottky testing and steady-state and time-resolved emission spectroscopy, the main reason for enhanced photocatalytic activity is the faster electron transfer from CdSe QDs to {001}-TiO2 compared with to {101}-TiO2. This research on tailored facets in QD/TiO2 composites provides primary insights for the design of effective photocatalysts.
- Chen, Weiwei,Yu, Shan,Zhong, Yunqian,Fan, Xiang-Bing,Wu, Li-Zhu,Zhou, Ying
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- Low-temperature synthesis of anatase TiO2 nanoparticles with tunable surface charges for enhancing photocatalytic activity
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In this work, the positively or negatively charged anatase TiO2 nanoparticles were synthesized via a low temperature precipitation-peptization process (LTPPP) in the presence of poly(ethyleneimine) (PEI) and poly(sodium4- styrenesulfonate) (PSS). X-ray diffraction (XRD) pattern and high-resolution transmission electron microscope (HRTEM) confirmed the anatase crystalline phase. The charges of the prepared TiO2, PEI-TiO2 and PSS-TiO2 nanoparticles were investigated by zeta potentials. The results showed that the zeta potentials of PEI-TiO2 nanoparticles can be tuned from +39.47 mV to +95.46 mV, and that of PSS-TiO2 nanoparticles can be adjusted from -56.63 mV to -119.32 mV. In comparison with TiO2, PSS-TiO2 exhibited dramatic adsorption and degradation of dye molecules, while the PEI modified TiO2 nanoparticles showed lower photocatalytic activity. The photocatalytic performances of these charged nanoparticles were elucidated by the results of UV-vis diffuse reflectance spectra (DRS) and the photoluminescence (PL) spectra, which indicated that the PSS-TiO2 nanoparticles showed a lower recombination rate of electron-hole pairs than TiO2 and PEI-TiO2.
- Li, Ye,Qin, Zhenping,Guo, Hongxia,Yang, Hanxiao,Zhang, Guojun,Ji, Shulan,Zeng, Tingying
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- Enhanced photocatalytic degradation of Amaranth dye on mesoporous anatase TiO2: Evidence of C-N, NN bond cleavage and identification of new intermediates
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The photocatalytic degradation mechanism of Amaranth, a recalcitrant carcinogenic azo dye, was investigated using mesoporous anatase TiO2 under sunlight. Mesoporous anatase TiO2 of a high photocatalytic activity has been synthesized using a sol-gel method and its photocatalytic activity for the degradation of Amaranth dye has been evaluated with respect to Degussa P25. The effect of bi-dentate complexing agents like oxalic acid, ethylene glycol and urea on the surface properties of TiO2 catalyst has been investigated using TG-DTA, FTIR, HR-TEM, SAED, PXRD, EDS, UV-DRS, PL, BET N2 adsorption-desorption isotherm studies and BJH analysis. The influence of catalyst properties such as the mesoporous network, pore volume and surface area on the kinetics of degradation of Amaranth as a function of irradiation time under natural sunlight has been monitored using UV-Vis spectroscopy. The highest rate constant value of 0.069 min-1 was obtained for the photocatalytic degradation of Amaranth using TiO2 synthesized via a urea assisted sol-gel synthesis method. The effect of the reaction conditions such as pH, TiO2 concentration and Amaranth concentration on the photodegradation rate has been investigated. The enhanced photocatalytic activity of synthesized TiO2 in comparison with P25 is attributed to the mesoporous nature of the catalyst leading to increased pore diameter, pore volume, surface area and enhanced charge carrier separation efficiency. New intermediates of photocatalytic degradation of Amaranth, namely, sodium-3-hydroxynaphthalene-2,7-disulphonate, 3-hydroxynaphthalene, sodium-4-aminonaphthalenesulphonate and sodium-4-aminobenzenesulphonate have been identified using LC-ESI-MS for the very first time, providing direct evidence for simultaneous bond cleavage pathways (-C-N-) and (-NN-). A new plausible mechanism of TiO2 catalysed photodegradation of Amaranth along with the comparison of its toxicity to that of its degradation intermediates and products is proposed.
- Naik, Amarja P.,Salkar, Akshay V.,Majik, Mahesh S.,Morajkar, Pranay P.
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- Fabrication and characterization of nano TiO2 thin films at low temperature
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Anatase TiO2 thin films were successfully prepared on glass slide substrates via a sol-gel method from refluxed sol (RS) containing anatase TiO2 crystals at low temperature of 100 °C. The influences of various refluxing time on crystallinity, morphology and size of the RS sol and dried TiO2 films particles were discussed. These samples were characterized by infrared absorption spectroscopy (FT-IR), X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission-scanning electron microscopy (FE-SEM) and UV-vis absorption spectroscopy (UV-vis). The photocatalytic activities of the TiO2 thin films were assessed by the degradation of methyl orange in aqueous solution. The results indicated that titania films thus obtained were transparent and their maximal light transmittance exceeded 80% under visible light region. The TiO2 thin films prepared from RS-6 sol showed the highest photocatalytic activity, when the calcination temperature is higher than 300 °C. The degradation of methyl orange of RS-6 thin films reached 99% after irradiated for 120 min, the results suggested that the TiO2 thin films prepared from RS sol exhibited high photoactivities.
- Ge, Lei,Xu, Mingxia,Sun, Ming,Fang, Haibo
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- Redox processes in fine-particle TiO2-Cr2O 3 oxides
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We have studied the stability of the Cr6+ ion in fine-particle TiO2-Cr2O3 oxides during storage after calcination in air. The results indicate that, during storage under normal conditions for 720 days, Cr6+
- Belaya,Viktorov
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- Systematic study of TiO2/ZnO mixed metal oxides for CO2 photoreduction
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A two component three degree simplex lattice experimental design was employed to evaluate the impact of different mixing fractions of TiO2 and ZnO on an ordered mesoporous SBA-15 support for CO2 photoreduction. It was anticipated that the combined advantages of TiO2 and ZnO: low cost, non-toxicity and combined electronic properties would facilitate CO2 photoreduction. The fraction of ZnO had a statistically dominant impact on maximum CO2 adsorption (β2 = 22.65, p-value = 1.39 × 10-4). The fraction of TiO2 used had a statistically significant positive impact on CO (β1 = 9.71, p-value = 2.93 × 10-4) and CH4 (β1 = 1.43, p-value = 1.35 × 10-3) cumulative production. A negative impact, from the interaction term between the fractions of TiO2 and ZnO, was found for CH4 cumulative production (β3 = -2.64, p-value = 2.30 × 10-2). The systematic study provided evidence for the possible loss in CO2 photoreduction activity from sulphate groups introduced during the synthesis of ZnO. The decrease in activity is attributed to the presence of sulphate species in the ZnO prepared, which may possibly act as charge carrier and/or radical intermediate scavengers.
- Thompson, Warren A.,Olivo, Alberto,Zanardo, Danny,Cruciani, Giuseppe,Menegazzo, Federica,Signoretto, Michela,Maroto-Valer, M. Mercedes
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- Dependence of nitrogen doping on TiO2 precursor annealed under NH3 flow
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N-doped TiO2 photocatalysts were prepared by annealing two different precursors, P25 and a TiO2 xerogel powder under NH3/Ar flow at 500, 550, and 600 °C. The xerogel powder prepared by peptizing Ti(OH)4 with HNO3 was composed of nanoparticles and had large specific surface area. During the annealing process, the xerogel powder underwent increase in crystallinity, grain growth and phase transformation, whereas P25 did not show obvious changes. Compared with the N-doped TiO2 photocatalysts from P25, the N-doped TiO2 photocatalysts from the xerogel powder possessed higher concentrations of the substitutional nitrogen and exhibited more obvious absorption in the visible light region. The N-doped TiO2 photocatalysts from the xerogel powder exhibited obvious visible-light activities for photodegrading methylene blue and the sample prepared at 500 °C achieved the best performance with a rate constant (k) about 0.44 h-1, whereas those from P25 did not exhibit improved visible-light activities.
- Fang, Xiaoming,Zhang, Zhengguo,Chen, Qinglin,Ji, Hongbing,Gao, Xuenong
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- Layer-by-layer self-assembled hollow titania composite nanospheres containing [60]fullerene
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Core-shell nanospheres, titania composite nanospheres containing [60]fullerene, were fabricated with sizes of about 100 nm by a layer-by-layer self-assembly procedure, and were characterized by TGA, FT-IR and XPS spectroscopy. The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
- Jiang, Wenfeng,Yu, Ying,Li, Dianqing,Zhao, Yingjie,Xu, Maoyou,Shi, Zhiqiang
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- Structure Sensitivity of Au-TiO2 Strong Metal–Support Interactions
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Strong metal–support interactions (SMSI) is an important concept in heterogeneous catalysis. Herein, we demonstrate that the Au-TiO2 SMSI of Au/TiO2 catalysts sensitively depends on both Au nanoparticle (NP) sizes and TiO2 facets. Au NPs of ca. 5 nm are more facile undergo Au-TiO2 SMSI than those of ca. 2 nm, while TiO2 {001} and {100} facets are more facile than TiO2{101} facets. The resulting capsulating TiO2?x overlayers on Au NPs exhibit an average oxidation state between +3 and +4 and a Au-to-TiO2?x charge transfer, which, combined with calculations, determines the Ti:O ratio as ca. 6:11. Both TiO2?x overlayers and TiO2?x-Au interface exhibit easier lattice oxygen activation and higher intrinsic activity in catalyzing low-temperature CO oxidation than the starting Au-TiO2 interface. These results advance fundamental understanding of SMSI and demonstrate engineering of metal NP size and oxide facet as an effective strategy to tune the SMSI for efficient catalysis.
- Zhang, Yunshang,Liu, Jin-Xun,Qian, Kun,Jia, Aiping,Li, Dan,Shi, Lei,Hu, Jun,Zhu, Junfa,Huang, Weixin
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- Control of phase and pore structure of titania powders using HCl and NH4OH catalysts
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Porous titania powders were prepared by hydrolysis of titanium tetraisopropoxide (TTIP) and were characterized at various calcination temperatures by nitrogen adsorption, X-ray diffraction, and microscopy. The effect of HCl or NH4OH catalysts a
- Song, Ki Chang,Pratsinis, Sotiris E.
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- Synthesis and properties of titanium glycolate Ti(OCH2CH 2O)2
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A new efficient method for the synthesis of extended micro-and nano-sized crystals (whiskers, fibers) of titanium glycolate Ti(OCH2CH 2O)2 has been suggested. The method implies the reaction of hydrated titanium dioxide with ethylene glycol on heating in air. Thermolysis of Ti(OCH2CH2O)2 in air gives titanium dioxide as anatase (400-500°C) and rutile (T > 700°C), the morphology of titanium glycolate crystals being inherited by the oxide. The pseudocrystals of the thermolysis product in an inert gas medium (T = 500-950°C) represent aglomeration of nano-sized titanium dioxide particles and amorphous carbon. At temperatures up to 1300°C, the formation of the TiO2-x C x phase with a rutile structure is probable. In a wet air environment, titanium glycolate is partially hydrolyzed to give TiO x (OCH2CH2O)2-2x (OH)2x ?xH 2O (0 ≤ x ≤ 1) and on keeping in water at room temperature, ethylene glycol is completely displaced from the crystals. This process is also not accompanied by changes in the particle morphology.
- Krasil'nikov,Shtin,Gyrdasova,Polyakov,Shveikin
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- Sulfate-promoted titania photocatalyst for high efficiency gas phase toluene degradation
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A regenerable, halide-free, sulfate-promoted titania photocatalyst was developed for the high-efficiency, room temperature gas phase photodegradation of toluene at higher than trace concentrations. Copyright
- Barraud, Elodie,Bosc, Florence,Keller, Nicolas,Keller, Valerie
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- Hydrothermal synthesis of single-crystalline perovskite PbTiO3 nanosheets with dominant (001) facets
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Single-crystalline tetragonal perovskite lead titanate (PbTiO3) nanosheets with dominant (001) facets have been successfully synthesized by employing layered K2Ti6O13 nanofibers as titanium sources. The as-prepared PbTiO3 nanosheets were characterized by means of X-ray diffraction, field-emission scanning electron microscopy, transmission electron microscopy (TEM), high-resolution TEM, and selected-area electron diffraction. In order to understand the formation mechanism of the PbTiO3 nanosheets, a series of time-dependent experiments were performed. Because of the substitution of Pb2+ ions for K+ ions, the TiO6 octahedral lamellas exfoliate from the layered K2Ti6O13 crystal structure. Then the exfoliated TiO6 octahedral lamellas as templates transform to lamellar PbTiO3 species by reacting with the dehydrated Pb2+ ions. With hydrothermal treatment prolongation, the lamellar PbTiO3 species crystallize to single-crystalline PbTiO3 nanosheets. Moreover, the thickness of the synthesized single-crystalline PbTiO3 nanosheets can be tailored in the range of 10-50 nm by controlling the hydrothermal treatment time. In addition, the band gap and the optoelectronic properties of the single-crystalline PbTiO3 nanosheets are investigated by UV-vis absorption and photoluminescence. (Figure Presented).
- Deng, Shiqi,Xu, Gang,Bai, Huiwen,Li, Lingling,Jiang, Shan,Shen, Ge,Han, Gaorong
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- Supported Au Catalysts Prepared from Au Phosphine Complexes and As-Precipitated Metal Hydroxides: Characterization and Low-Temperature CO Oxidation
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Supported Au catalysts were prepared by attaching Au phosphine complexes, Au(PPh3)(NO3) (1) and [Au9(PPh3)8](NO3)3 (2), on as-precipitated metal hydroxides M(OH)*x (*, as-precipitated; M = Mn2+, Co2+, Fe3+, Ni2+, Zn2+, Mg2+, Cu2+, Ti4+, Ce4+, and La3+), followed by temperature-programmed calcination in a flow of dry air. The obtained Au catalysts showed high catalytic activities in low-temperature CO oxidation. Among the obtained Au catalysts 1/Mn(OH)*2 and 1/Co(OH)*2 were most highly active even at 203 K. 1/Fe(OH)*3 and 1/Ti(OH)*4 also catalyzed CO oxidation at low temperatures 203-273 K, whereas 1/Fe2O3 and 1/TiO2 prepared by supporting 1 on conventional Fe2O3 and TiO2 showed negligible activity under the similar reaction conditions. It was estimated by TEM and XRD that the mean diameter of Au particles in 1/Fe(OH)*3 was about 2.9 nm, which was about 10 times smaller than that for 1/Fe2O3. EXAFS for 1/Ti(OH)*4 revealed that the coordination number of Au-Au bond was 8-10, while that for 1/TiO2 was 11.0, which also indicates that Au particle size for 1/Ti(OH)*4 is smaller than that for 1/TiO2. The catalysts obtained by attaching the Au complexes on commercially available metal hydroxides also showed negligible activity for the low-temperature CO oxidation under identical conditions. These results demonstrate that supported Au catalysts with small Au particles, tremendously active for the low-temperature CO oxidation, can be prepared by attaching the Au phosphine complexes on the as-precipitated metal hydroxides. Sodium cations exhibited positive effect on the Au catalysis, whereas chloride anions drastically decreased the CO oxidation activity.
- Yuan, Youzhu,Kozlova, Anguelina P.,Asakura, Kiyotaka,Wan, Huilin,Tsai, Khirui,Iwasawa, Yasuhiro
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- STUDY OF SO2 ADSORPTION ON TITANIUM DIOXIDE BY IR SPECTROSCOPY AND THERMAL DESORPTION
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The oxides of aluminium and titanium are active catalysts for the Claus process.IR spectroscopy has been used to identify a number of forms of SO2 adsorbed on γ-Al2O3 capable of participating in this reaction.The adsorption of reagents on titanium oxide has been studied in greater detail: there is a fair amount of information available on the nature of the adsorption of SO2 on rutile.In this work we have investigated the adsorption of the forms of SO2 on the surface of TiO2 (anatase).
- Dubkov, A. A.,Shor, A. M.,Pavlenko, N. I.,Anshits, A. G.
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- TAP study on carbon monoxide oxidation over supported gold catalysts Au/Ti(OH)*4 and Au/Fe(OH)*3: Moisture effect
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The effect of moisture on the behavior of the active supported gold catalysts developed by us, Au/Ti(OH)*4 (I) and Au/Fe(OH)*3 (II), during CO activation and CO oxidation in the temperature range 298-473 K was investigated by the temporal analysis of products (TAP) technique. The oxidation reaction over the Au/Ti(OH)*4 catalyst was totally suppressed by the presence of water, independent of the water content of 200 and 1000 ppm, the carbon monoxide-to-oxygen ratio, and the temperature. In contrast, the presence of water vapors showed no effect on CO oxidation over the Au/Fe(OH)*3 catalyst. For both catalysts, the carbon monoxide adsorption feature was unalterable by the presence of water, namely CO molecules reversibly adsorbed on the catalyst surface, but the amount of CO adsorbed decreased by increasing water content. When a reaction mixture at a 1:1 ratio of CO to O2 was pulsed on the catalyst in the absence of water, the CO response curve showed two peaks, whereas in the presence of water, the TAP response curve showed only one peak. At a 1:3 CO-to-O2 ratio, the CO response curve showed only one peak, which shifted to a shorter time and narrowed in the absence of water. The shift was more pronounced on catalyst (II). The TAP experiments provided indirect evidence that CO and water adsorbed together (CO weakly and water strongly) and water blocked [irreversibly for Au/Ti(OH)*4 and reversibly for Au/Fe(OH)*3], the adsorption sites for oxygen.
- Olea, Maria,Tada, Mizuki,Iwasawa, Yasuhiro
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- Supported ionic liquid [Bmim]FeCl4/Am TiO2 as an efficient catalyst for the catalytic oxidative desulfurization of fuels
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High activity oxidation of sulfur compounds to sulfones in extraction coupled with catalytic oxidative desulfurization (ECODS) system catalyzed by supported ionic liquid [Bmim]FeCl4/Am TiO2 was reported. The catalysts were analyzed by thermogravimetric (TG) analysis, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS). It was found that [Bmim]FeCl4 and Am TiO2 had a synergistic effect on the desulfurization system. Effects of calcination temperature of the catalyst and various reaction conditions on the catalytic activity of desulfurization were investigated. Moreover, GC-MS analyses were employed to prove the process of the desulfurization. As a solid catalyst, the supported ionic liquid could be separated from the reaction easily. The recycling tests showed that the desulfurization efficiency remained 100% after reusing it for 25 times. Therefore, the ECODS system has excellent reusability and is promising for industrial applications for catalytic oxidative desulfurization.
- Xun, Suhang,Zhu, Wenshuai,Zheng, Dan,Li, Hongping,Jiang, Wei,Zhang, Ming,Qin, Yuejiao,Zhao, Zhen,Li, Huaming
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- Nanosized anatase TiO2 as precursor for preparation of sulfated titania catalysts
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Nanosized anatase TiO2 has been prepared by a sol-gel hydrothermal process. The effect of water:alkoxide molar ratio, hydrothermal aging temperature and aging time on the properties of the nanocrystalline anatase TiO2 was investigated in detail. The specific surface area, sulfur content and surface acidity of sulfated titania catalysts prepared by sulfation of sol-gel hydrothermal derived nanocrystalline TiO2 were greater than those of the analogous catalyst prepared from ordinary amorphous titania hydrate. The former catalysts displayed higher catalytic activities in isopropanol dehydration, cumene cracking and n-pentane conversion reactions. The influence of the crystalline state and crystalline grain of titania precursors on the properties of sulfated titania catalysts was studied and discussed.
- Ma, Zhen,Yue, Yinghong,Deng, Xingyi,Gao, Zi
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- Electrodes based on nanodispersed titanium and tungsten oxides for a sensor of dissolved oxygen
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It is suggested to use films of nanodispersed Ti and W oxides as electrodes in a sensor for dissolved oxygen. It is shown that films of this kind have stable characteristics in electroreduction of O2 in saline. Pleiades Publishing, Inc., 2006.
- Kolbasov,Vorobets,Korduban,Shpak,Medvedskii,Kolbasova,Linyucheva
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- Chemical synthesis, structural, thermo-physical and electrical property characterization of PLZT ceramics
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The sol-gel process was employed to prepare (Pb1-xLax)(Zr1-yTiy)O3 (PLZT) ceramics with nominal composition (Pb0.92La0.08)(Zr0.60Ti0.40)O3. X-ray diffraction results showed that the perovskite PLZT phase is formed at room temperature itself. The average size distribution of the particles was obtained by small angle X-ray scattering (SAXS). Nano-crystalline particles with a size of the order of ~30 nm were found. Morphological studies were carried out by SEM analyses to observe the grain structure. TG-DTA and DSC studies were used to analyze the thermal properties of the nano-powders, in order to understand the reaction kinetics in them. Poled bulk ceramic samples prepared from the sol-gel derived powders were subjected to electrical measurements, in order to determine the piezoelectric and electromechanical coupling coefficients.
- James,Kumar, Rajesh,M., PremKumar,Srinivas,Radha,Vithal,Vijayakumar
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- Improved Photodegradation of Organic Contaminants Using Nano-TiO2 and TiO2-SiO2 Deposited on Portland Cement Concrete Blocks
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The photocatalytic activity of TiO2 nanoparticles (nano-TiO2) and its hybrid with SiO2 (nano-TiO2-SiO2) for degradation of some organic dyes on cementitious materials was studied in this work. Nanohybrid photocatalysts were prepared using an inorganic sol-gel precursor and then characterized using XRD, SEM and UV-Vis. The grain sizes were estimated by Scherrer's equation to be around 10 nm. Then, a thin layer was applied to Portland cement concrete (PCC) blocks by dipping them into nano-TiO2 and nano-TiO2-SiO2 solution. The efficiency of coated PCC blocks for the photocatalytic decomposition of two dyes, Malachite Green oxalate (MG) and Methylene Blue (MB), was examined under UV and visible irradiation and then monitored by the chemical oxygen demand tests. The results showed that more than 80% and 92% of MG and MB were decomposed under UV-Vis irradiation using blocks coated with nano-TiO2-SiO2. TiO2/PCC and TiO2-SiO2/PCC blocks showed a significant ability to oxidize dyes under visible and UV lights and TiO2-SiO2/PCC blocks require less time for dye degradation. Based on these results, coated blocks have increased photocatalytic activity which can make them commercially accessible photocatalysts.
- Jafari, Hoda,Afshar, Shahrara
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- Hierarchically porous TiO2/SiO2 fibers with enhanced photocatalytic activity
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While TiO2 nanoparticles are one of the most promising photocatalysts, their applications have been greatly hindered by easy aggregation. One of the effective routes to solve this problem is to incorporate them on/in a solid carrier. In this paper, we report the fabrication of hierarchically porous TiO2/SiO2 fibers via an electrospinning technique combined with subsequent high-temperature calcination treatment, in which the hierarchically porous SiO2 fibers confer a platform to assemble TiO2 nanoparticles with a uniform spatial distribution. The resultant hierarchically porous TiO2/SiO 2 fibers have shown an enhanced photocatalytic activity with ~95% degradation of rhodamine B as compared to ~75% using our synthesized TiO2 nanoparticles and ~77% using commercially available Degussa P25 after 120 min illumination.
- Hou, Huilin,Wang, Lin,Gao, Fengmei,Wei, Guodong,Zheng, Jinju,Tang, Bin,Yang, Weiyou
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- The direct reaction between CO2 and phenol catalyzed by bifunctional catalyst ZrO2
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The systematic investigation was carried out to elucidate the direct reaction between CO2 and phenol over multiphase catalyst. Reactions carried out over ZrO2, TiO2, and KF/NaY + Mn2+ gave the high selectivity t
- Li, Zhenhuan,Su, Kunmei
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- Influence of sodium chloride and dibasic sodium phosphate salt matrices on the anatase-rutile phase transformation and particle size of titanium dioxide powder
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The influence of sodium chloride (NaCl) and dibasic sodium phosphate (Na2HPO4·2H2O, DSP) on the phase transformation and particle size of titanium dioxide powder had been investigated. The salt matrix was shown to suppress both the amorphous to anatase transition and the anatase to rutile transition. DSP was particularly effective. Irrespective of the additives, transformation versus time curves of the anatase to rutile conversion were observed to be sigmoidal, and were interpreted in terms of a first order, nucleation-growth controlled phenomenon. Analysis of these curves using appropriate rate laws yielded activation energies for nucleation of ~4.3 eV for NaCl salt matrix and ~8.6 eV for DSP salt matrix, compared with ~3.2 eV for a sample with no salt. Activation energies for the growth or propagation stage were ~5 and ~8.9 eV for NaCl and DSP powders, respectively, compared with ~3.8 eV for no salt. In the solid state, salt matrices suppressed the particle growth as well. These behaviors, in general are thought to be governed by the presence of salt impurities, especially anions chemisorbed at the surface.
- Roy, Banasri,Fuierer, Paul Anton
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- Gas phase photocatalytic removal of toluene effluents on sulfated titania
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Photocatalytic removal of toluene in the gas phase was carried out over UV-illuminated sulfated titania materials in a cylinder-like continuous reactor. A series of SO42 - TiO2 samples was obtained from the addition of H2SO4 on an amorphous titanium hydroxide gel synthesized according to a classical sol-gel procedure. The wide variety of materials led to varying photocatalytic behaviors depending strongly on the experimental synthesis parameters, having a determinant influence on the surface specific area, the crystallinity of the material, the crystallographic nature of TiO 2, and the sulfate surface content. Optimization of the experimental parameters, such as the molarity of the sulfation solution, varying in the range 0.25-5 M leading to surface sulfate coverage of 2.5-14 wt%, and the calcination temperature ranging from 400 to 800 °C, promoted enhanced photocatalytic performance toward toluene removal as compared with commercially available P25 TiO2 and sulfate-free sol-gel TiO2. The most efficient photocatalyst was obtained for a near-monolayer sulfate coverage corresponding to the presence of both TiO2 and well-dispersed SO42- with optimized contact between SO42- and TiO2 domains. Furthermore, a positive role of sulfates is attributed both to an electron transfer from titanium to sulfates, leading to a positive charge trap effect, and to better desorption of electron-rich sp2-bound carbon aromatic poisons, thus limiting deactivation.
- Barraud, Elodie,Bosc, Florence,Edwards, David,Keller, Nicolas,Keller, Valerie
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- Acid-redox properties of titania-supported 12-molybdophosphates for methanol oxidation
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Physicochemical and catalytic properties of titania-supported 12- molybdophosphates have been investigated. The samples were characterized by the S(BET) method, Fourier-transform infrared (FTIR) and X-ray photoelectron (XPS) spectroscopies, temperature-programmed desorption (TPD) of ammonia and temperature-programmed reduction (TPR). The effect of temperature pretreatment on the catalytic behaviour of the samples in methanol oxidation was investigated. A significant change of selectivity to the main reaction products: dimethyl ether (DME) and formaldehyde (HCHO), as a function of the acid properties of the catalysts was observed. The highest selectivity to DME at 523 K suggested that the undecomposed molybdophosphoric acid (HPMo) on titania behaves as an acid catalyst. Pretreatment of the samples at higher temperatures (up to 723 K) and replacement of the protons in HPMo by cations (Co and Ni) lead to development of the redox properties (HCHO formation) of the catalyst, due to the suppression of the Bronsted acidity. The IR and XPS results provided clear evidence for the preservation of Keggin unit up to 623 K pretreatment after test reaction.
- Damyanova,Cubeiro,Fierro
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- Site Sensitivity of Interfacial Charge Transfer and Photocatalytic Efficiency in Photocatalysis: Methanol Oxidation on Anatase TiO2 Nanocrystals
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Photocatalytic oxidation of methanol on various anatase TiO2 nanocrystals was studied by in situ and time-resolved characterizations and DFT calculations. Surface site and resulting surface adsorbates affect the surface band bending/bulk-to-surface charge migration processes and interfacial electronic structure/interfacial charge transfer processes. TiO2 nanocrystals predominantly enclosed by the {001} facets expose a high density of reactive fourfold-coordinated Ti sites (Ti4c) at which CH3OH molecules dissociate to form the CH3O adsorbate (CH3O(a)Ti4c). CH3O(a)Ti4c localized density of states are almost at the valence band maximum of TiO2 surface, facilitating the interfacial hole transfer process; CH3O(a)Ti4c with a high coverage promotes upward surface band bending, facilitating bulk-to-surface hole migration. CH3O(a)Ti4c exhibits the highest photocatalytic oxidation rate constant. TiO2 nanocrystals enclosed by the {001} facets are most active in photocatalytic methanol oxidation.
- Fu, Cong,Li, Fei,Zhang, Jiachen,Li, Dan,Qian, Kun,Liu, Yong,Tang, Junwang,Fan, Fengtao,Zhang, Qun,Gong, Xue-Qing,Huang, Weixin
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- Preparation of graphene/TiO2 anode materials for lithium-ion batteries by a novel precipitation method
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This paper reports a large-scale production route for graphene/TiO 2 nanocomposites using water-based in situ precipitation method. In this method, freshly prepared graphene oxides/TiO2 obtained by precipitating Ti(SO4)su
- Ding, Yan-Huai,Zhang, Ping,Ren, Hu-Ming,Zhuo, Qin,Yang, Zhong-Mei,Jiang, Yong
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- Preparation, Characterization, and Photoactivity of Polycrystalline Nanostructured TiO2 Catalysts
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Various preparations of nanostructured TIO2 starting from Ti(iso-OC3H7)4 or TiCl4 are reported. The samples were characterized by X-ray diffractometry, specific surface area and porosity determinations, scanning and transmission electron microscopy, and diffuse reflectance spectroscopy. 4-Nitrophenol photodegradation in aqueous medium was employed as a probe reaction to test the photoactivity of the catalysts. The photoactivity of some samples derived from Ti(iso-OC 3H7)4 was found comparable with that of commercial powders. Calcination after the hydrolysis process was necessary to achieve crystallization of the particles before using them as photocatalysts for the reaction studied. The samples deriving from TiCl4 were the most photoactive among the home-prepared catalysts, and neither filtration nor calcination was needed to obtain a highly photoactive anatase phase.
- Addamo, Maurizio,Augugliaro, Vincenzo,Di Paola, Agatino,García-López, Elisa,Loddo, Vittorio,Marcí, Giuseppe,Molinari, Raffaele,Palmisano, Leonardo,Schiavello, Mario
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- New insights for titanium(iv) speciation in acidic media based on UV-visible and31P NMR spectroscopies and molecular modeling
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Titanium chemistry in aqueous acidic media has been extensively investigated over the last decades. Hydrolyzed species such as Ti(OH)3+, TiO2+, Ti(OH)22+or Ti(OH)3+have been identified and their equilibria have been studied in nitric and perchloric acid. A predominance of the divalent cations was found for low pH (i.e., pH 0.1 mol L?1), as stable precursors for the formation of condensed titanium dioxide. The present paper reconsiders firstly previous knowledge about the speciation of titanium(iv) in non-complexing acidic media by giving evidence for the presence of polynuclear hydrolyzed species, even at very low Ti(iv) concentration (i.e., typically ?1). UV-visible absorbance spectra recorded for diluted nitric acid solutions (a model of non-complexing acidic medium) containing titanium(iv) were compared to time-dependent density functional theory (TD-DFT) predicted excitation energies. Experimental and predicted maximal absorbance wavelengths showed significantly improved matches when polynuclear species were considered in TD-DFT calculation. Then, 0.1-12.7 mol L?1phosphoric acid solutions containing titanium(iv) were studied by means of spectroscopic techniques (UV-visible, NMR) in order to identify qualitatively the presence of titanium(iv) complexes and to link this speciation to the acid concentration. Two different titanium(iv) orthophosphate complexes, potentially polynuclear, were detected, and the presence of free titanium(iv) is also expected for low phosphoric acid concentration (i.e., ?1). A general complexation scheme for a large range of H3PO4concentration was thus formulated.
- Chagnes, Alexandre,Cote, Gérard,Halleux, Hubert,Leclerc, Sébastien,Mangold, Lucas,Moncomble, Aurélien
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- Preparation of WO3-modified TiO2 thin film by peroxo sol–gel method and its photocatalytic activity in degradation of methylene blue
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A series of WO3-modified TiO2 sols with various WO3 contents were synthesized by peroxo sol–gel method using H2O2 as the agent. The as-synthesized WO3-TiO2 sols were light yellow in color. The maximum amount of WO3 which could be incorporated into the TiO2 sol was 4?wt.percent. The pH values of the as-prepared sols were near neutral. These sols were very stable even after 2?years in stock. The sols were used to coat on glass substrate. The XRD patterns and the SAED patterns indicated that the phase of TiO2 was anatase. There were no characteristic XRD peaks of WO3 in the WO3-modified TiO2 sol, possibly due to low WO3 loading. The particles were rhombus shaped with the major axis and minor axis of 30–77?nm and 15–31?nm, respectively. WO3 was incorporated into the surface structure of TiO2 and modified the electronic state of Ti. The film coated onto glass substrate was very uniform, and the film thickness was ~ 160?nm. The XPS results exhibited that W existed as 5 + and 6 + oxidation states and Ti existed in Ti3+ and Ti4+. These four chemical states play a role of gathering the photogenerated holes and capturing the photogenerated electrons in the lower conduction band of WO3, respectively. This can effectively enhance the separation rate of photogenerated electron–hole pairs and increase the photoactivity. WO3/TiO2 samples had high photocatalytic activity under UV light illumination to degrade methylene blue, because it had high OH and O2? group contents.
- Chen, Yu-Wen,Wu, Jia-Ying
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- Humic acid mediated toxicity of faceted TiO2 nanocrystals to Daphnia magna
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Nano-bio interface is of great importance in dictating the interaction between the nanomaterials and biological system and thus the toxicity to aquatic organisms. Herein, two specific faceted TiO2 nanocrystals, {101} and {001} facet, were exposed to Daphnia magna to explore facet-dependent toxicological responses in aquatic environment. Due to the different influences on oxidative stress process, the half-maximal effective concentration (EC50) value of {001} TiO2 (1.27 g L-1) to D. magna was less than that of {101} TiO2 (1.68 g L-1). Suwannee river humic acid (SRHA) could significantly reduce the oxidative stress responses of TiO2 nanocrystals and thus alleviate their toxicities to D. magna in aquatic environment. The protective effect of SRHA against TiO2 toxicity exhibited a facet-dependent manner. Compared to {101} TiO2, a more obvious detoxification effect was observed for {001} TiO2. The high SRHA concentration could endow both faceted TiO2 nanocrystals with a similar toxicity due to the formation of SRHA-corona on TiO2 surface. This facet-affected toxicity of nanomaterials in aquatic environment would provide us new insights in predicting the exposure risk of nanomaterials in nature waters.
- Lu, Yi,Zhang, Hui,Wang, Hua,Ma, Ning,Sun, Tao,Cui, Baoshan
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- Influence of transition metals on the surface acidic properties of titania prepared by sol-gel route
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A series of titania catalysts containing chromium, molybdenum as well as tungsten has been prepared by colloidal sol-gel route using metatitanic acid as the precursor. Structural characterization of the prepared catalysts was done with Energy dispersive X-ray analysis, X-ray diffraction, BET surface area and pore volume measurements. The influence of different transition metals like chromium, molybdenum and tungsten on the surface acidic properties of titania is investigated in detail. Two independent methods have been used to study the surface acidity of these catalyst systems: temperature programmed desorption of ammonia which is a measure of total acidity and thermodesorption studies using 2,6-dimethyl pyridine which is a measure of Bronsted acidity. Cumene cracking reaction is carried out over the prepared systems for further characterizing the acidity of the prepared catalysts. Remarkable enhancement in the surface acidity is observed after transition metal incorporation. The catalytic activity of the prepared catalysts was tested towards the dehydrogenation of cyclohexane.
- Shali,Sugunan
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- Quantitative Analysis of the Morphology of {101} and {001} Faceted Anatase TiO2 Nanocrystals and Its Implication on Photocatalytic Activity
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The atomistic structure and morphology (shape and size) of nanomaterials have strong influences on their physical and chemical properties. However, many characterization techniques focus exclusively on one length-scale regime or another when developing quantitative morphology/structural models. In this article, we demonstrate that powder X-ray diffraction and neutron pair distribution function (PDF) can be used to obtain accurate average morphology and atomistic structure of {001} and {101} faceted anatase TiO2 nanocrystals based on differential evolution refinements using Debye scattering equation calculations. It is also demonstrated that the morphology polydispersity of TiO2 nanocrystals can be effectively obtained from the diffraction data via a numerical refinement routine. The morphology refinement results are in good agreement with those from transmission electron microscopy and the modeling of small angle neutron scattering data. This method is successfully used to quantify the facet-specified photocatalytic hydrogen evolution activity of anatase TiO2 nanocrystals with different {001} to {101} ratios. It is found that the sample with an intermediate amount of both {001} and {101} facets shows the best photocatalytic hydrogen evolution reaction (HER) activity. It is expected that the simultaneous structure and morphology refinement technique can be generally used to study the relationship between morphology and functionality of nanomaterials.
- Liu, Jue,Olds, Daniel,Peng, Rui,Yu, Lei,Foo, Guo Shiou,Qian, Shuo,Keum, Jong,Guiton, Beth S.,Wu, Zili,Page, Katharine
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- Synthesis and ionic conductivity of lithium-conducting titanium phosphate solid electrolytes
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Solid electrolytes were synthesized in the systems Li2O-Al 2O3-TiO2-P2O5 and Li 2O-Al2O3-TiO2-P2O 5-H2O-H2O2. Their ionic conductivities were studied and compared. The possibility of obtaining a film of Li1.3Al0.3Ti1.7(PO4)3 solid electrolyte on a sapphire substrate from an aqueous peroxide solution of a precursor was analyzed.
- Kunshina,Gromov,Kuz'min,Seitenova,Lokshin,Kalinnikov
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- Studies of the photocatalytic and electrochemical performance of the Fe2O3/TiO2 heteronanostructure
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The α-Fe2O3/TiO2 nanostructure material, synthesized on FTO (fluorine-doped tin oxide) substrate using the hydrothermal method at 180?°C for 5?h, exhibits an enhanced performance in the photocatalytic degradation of an organic dye. The optical band gap was found to decrease compared to the TiO2 one. The photocatalytic performances of the as-prepared heterojunction were evaluated with the degradation of methylene blue (MB) in an aqueous medium. The results revealed that the photocatalytic activity of the Fe2O3/TiO2/FTO was much higher than that of the pure TiO2. In addition, the photocurrent of the Fe2O3/TiO2/FTO heterojunction was remarkably higher than that of the bare TiO2 electrode. The obtained results indicate that the heterojunction formed between Fe2O3 and TiO2significantly improved the separation efficiency of the photo-generated electron–hole pairs. The electrochemical properties of the as-synthesized nanocomposite materials (α-Fe2O3/TiO2) were also evaluated with cyclic voltammetry for 1000 cycles. This nanocomposite exhibited an enhanced specific discharge capacity compared to the Fe2O3 nanomaterial. The as-produced material proved to have an impressive performance as a high-capacity anode for Na+-ion batteries.
- Othmani, Abdelhak,Kouass, Salah,Khalfi, Thamer,Bourchada, Sabrine,Touati, Fathi,Dhaouadi, Hassouna
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- A facile hydrothermal method for the controllable synthesis of TiO2 nanocrystals with tunable shapes
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The controllable preparation of anatase TiO2 nanocrystals with tunable shapes has drawn much attention recently. The general method used to prepare such nano-TiO2 involves the use of HF as a surfactant. However, the use of HF should be avoided due to its high risk. Therefore, the development of facile and friendly methods to controllably synthesize anatase TiO2 nanocrystals is important. In this research, instead of general titanium precursors, titanium peroxide sol was used as the raw material to synthesize anatase TiO2 nanocrystals due to its high stability in water. Oleic acid and oleylamine were used as capping surfactants. A hydrothermal method, without the use of high risk HF, was developed to prepare uniform anatase TiO2 nanocrystals with various shapes, which can be tuned from octahedral bipyramidal, to truncated octahedral bipyramidal, and then to nano-sheets. The ratio between {001} and {101} surfaces can be easily tuned by changing the amounts of oleic acid and oleylamine used. The photocatalytic activity of these anatase TiO2 nanocrystals was also evaluated through crystal violet photo-degradation under UV light illumination. It was shown that the anatase TiO2 nanocrystals can present a photocatalytic activity comparable to that of commercial P25.
- Nie, Shengchao,Zhao, Xiujian,Liu, Baoshun
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p. 103386 - 103393
(2015)
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- Sodium citrate functionalized reusable Fe3O4@TiO2 photocatalyst for water purification
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Easy-recycle photocatalysts are new materials for water treatment technologies. In order to improve the recyclable ability, we employed Fe3O4 particles, which were functionalized by sodium citrate, to serve as a substrate core to attract the deposition of a shell of TiO2 particles. When compared to the calcining process for preparing the composite, the TiO2 distributed homogeneously on the sodium citrate treated Fe3O4, forming a mesoporous shell layer. Due to the mesoporous structure, this Fe3O4@TiO2 exhibited high photocatalytic degradation activity to Rhodamine B, and it was easily recycled using a magnetic field to recover the catalyst from solution.
- Li, Wenyu,Wu, Haoyi
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- Room temperature synthesized BaTiO3 for photocatalytic hydrogen evolution
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As a photocatalyst, barium titanate (BaTiO3) has shown a great potential in photocatalytic water splitting for hydrogen evolution. In this work, BaTiO3 nanoparticles were synthesized at room temperature conditions under ambient pressure. The small particle size below 10 nm plays a key role in suppressing the recombination of photo-induced carriers, and thus promoting the photocatalytic activity. The photocatalytic hydrogen evolution rates of BaTiO3 (BTO-R) synthesized at room temperature are 8 and 2.9 times that of commercial BaTiO3 (BTO-C) in the presence and absence of triethanolamine (TEOA) as a sacrificial agent, respectively. This work provides a good example on size control, low-cost synthesis and photocatalysts' design.
- Chen, Tao,Meng, Jie,Wu, Shiyan,Pei, Jingyun,Lin, Qingyun,Wei, Xiao,Li, Jixue,Zhang, Ze
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- Amorphous titanic acid electrode: Its electrochemical storage of ammonium in a new water-in-salt electrolyte
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We report an amorphous titanic acid of TiO1.85(OH)0.30·0.28H2O as a new electrode for aqueous ammonium-ion batteries, which operates in a new water-in-salt electrolyte - 25 m NH4CH3COO. The titanic acid electrode exhibits a specific capacity nearly 8 times that from the crystalline TiO2 electrode. In electrochemical reactions, the amorphous titanic acid provides abundant storage sites in its disordered structure and affords strong H-bonding toward the inserted NH4+ ions.
- Holoubek, John J.,Jiang, Heng,Leonard, Daniel,Qi, Yitong,Bustamante, Galo C.,Ji, Xiulei
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- A process for the preparation of nitrobenzene derivative
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The invention provides a preparation method of nitrobenzene derivatives, which comprises the following steps: mixing aromatic amino-compound with sodium perborate, a titanic acid catalyst and glacial acetic acid, and reacting to obtain nitrobenzene derivatives, wherein the titanic acid catalyst is prepared by reacting isopropyl titanate and oxydol, and the aromatic amino-compound is a compound with an electrophilic substitution group in the ortho-position of the amino group. By using the sodium perborate as the oxidizer and the titanic acid catalyst as the cocatalyst, the reaction yield is up to 80-85%, and the product purity is up to 99% above.
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Paragraph 0034; 0035
(2016/10/10)
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- Photocatalysis in dimethyl carbonate green solvent: Degradation and partial oxidation of phenanthrene on supported TiO2
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Dimethyl carbonate (DMC) is here proposed-for the first time-as a green organic solvent for photocatalytic synthesis. In this work, the photocatalytic partial oxidation of phenanthrene in dimethyl carbonate (DMC) by using anatase TiO2as the photocatalyst is described as paradigmatic example of a green synthetic process starting from polycyclic aromatic hydrocarbons (PAHs). For comparison, the same reaction carried out also in ethanol, 1-propanol or 2-propanol is reported. The use of DMC as the solvent allowed us to achieve 19% and 23% selectivity towards 9-fluorenone and 6H-benzo[c]chromen-6-one, respectively. The proposed approach may represent both a new green synthetic process and an environmentally friendly route to degradation of PAHs. This journal is
- Bellardita,Loddo,Mele,Panzeri,Parrino,Pibiri,Palmisano
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p. 40859 - 40864
(2015/01/08)
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- RUTILE-TYPE TITANIUM DIOXIDE AND COSMETICS USING THE SAME
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A Rutile-type titanium dioxide having a rectangular particulate form configured such that major axial planes of rod-shaped particles having a minor axis diameter of 3 to 10 nm are oriented and aggregated in the minor axial direction, and a rod-shaped rutile-type titanium dioxide obtained by treating the rectangular rutile-type titanium dioxide with heat, wherein an apparent average major axial length of the oriented and aggregated particles is 100 to 400 nm, an apparent average minor axial length thereof is 30 to 150 nm, an apparent average axial ratio represented by apparent average major axial length/apparent average minor axial length is 2 to 5 and a specific surface area thereof is 10 to 100 m2/g.
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Paragraph 0040
(2014/05/07)
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- Characterization and reactivity of 11-molybdo-1-vanadophosphoric acid catalyst supported on zirconia for dehydration of glycerol to acrolein
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A series of vanadium-substituted phosphomolybdic acid (HPA) catalysts supported on zirconia were prepared by impregnation method with varying the HPA active phase content from 10 to 50 wt% on the support. The calcined catalysts were characterized by X-ray diffraction, Raman spectroscopy, temperature-programmed desorption of NH3, FT-IR spectra of pyridine adsorption and surface area measurements. XRD results suggest that the active phase of heteropolyacid is present in a highly dispersed state at lower loadings and as a crystalline phase at higher HPA loadings and these findings are well-supported by the results of FT-IR and Raman spectra. Calcination of the samples did not affect the Keggin ion structure of HPA. The ammonia TPD results suggest that acidity of the catalysts was found to increase with increase of HPA loading up to 40 wt% and decreases at higher loadings. FT-IR spectra of pyridine adsorption show that the Bronsted acidic sites increase with increase of HPA loadings up to 40 wt% catalyst. However, Lewis acid sites decrease with increase of HPA loading. Catalytic properties were evaluated during vapour phase dehydration of glycerol to acrolein. The catalyst with 40 wt% HPA has exhibited excellent selectivity towards acrolein formation with complete conversion of glycerol at 225°C under atmospheric pressure. Catalytic performances during dehydration of glycerol are well-correlated with acidity of the catalysts.
- Viswanadham, Balaga,Srikanth, Amirineni,Chary, Komandur V. R.
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p. 445 - 454
(2014/06/09)
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- Oxidative esterification of renewable furfural on gold-based catalysts: Which is the best support?
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Gold-based catalysts over different supports were investigated in the oxidative esterification of furfural by employing an efficient and sustainable process. The catalytic performances follow the trend: Zirconia-Au > Ceria-Au a‰
- Menegazzo, Federica,Signoretto, Michela,Pinna, Francesco,Manzoli, Maela,Aina, Valentina,Cerrato, Giuseppina,Boccuzzi, Flora
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p. 241 - 247
(2013/12/04)
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- Zr-La doped sulfated titania with a by far better catalytic activity and stability than pure sulfated titania in the esterification of acetic acid and n-butanol
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A novel solid superacid catalyst TiO2-Zr-La/SO4 2- was prepared by doping Zr and La to the bulk of TiO2. The modified TiO2-Zr-La/SO4 2- and the unmodified TiO2/SO4 2- were used to catalyze the esterification of acetic acid and n-butanol, in which these two catalysts were systematically compared in a lost of aspects such as catalytic activity and stability and so on. When a small amount of Zr and La were co-doped into the bulk of TiO2, the modified catalyst obtained a by far better catalytic activity and stability than the unmodified, showing that the modified is more resistive to deactivation than the unmodified. Under the set reaction conditions, the average conversion (of acetic acid) and the 20th-cycle conversion (of acetic acid) are 88.83 and 77.35 % for the modified, 80.83 and 46.15 % for the unmodified, respectively. The two catalysts were characterized by means of FTIR, XRD, BET, SEM, TG, and NH3-TPD methods to find the possible reasons for the superiority of the modified catalyst to the unmodified one. The characteristic results indicated that the incorporation of a small amount of Zr and La into the catalyst was beneficial to the modified catalyst: (1) improving its water-tolerance; (2) increasing its surface sulfate group content; (3) decreasing its crystallinity after calcination by retarding its crystallization from amorphous TiO2 to anatase TiO2; (4) increasing its specific surface area; (5) increasing its acidity including the concentration and acid strength of the surface acidic sites of it. All the above advantageous effects arisen from the two-element-doping are to be responsible for the substantially-improved catalytic performances of the modified catalyst.
- Shi, Wenping
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p. 732 - 738
(2013/07/26)
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- PROCESS FOR PREPARING MODIFIED V-Ti-P CATALYSTS FOR SYNTHESIS OF 2,3-UNSATURATED CARBOXYLIC ACIDS
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The invention relates to a catalyst composition comprising a mixed oxide of vanadium, titanium, and phosphorus modified with alkali metal. The titanium component is derived from a water-soluble, redox-active organo-titanium compound. The catalyst composition is highly effective at facilitating the vapor-phase condensation of formaldehyde with acetic acid to generate acrylic acid, particularly using an industrially relevant aqueous liquid feed.
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Paragraph 0131-0133
(2013/03/28)
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- Nano- and microagglomeration processes in the thermolysis of titanium and zirconium oxyhydrates
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Titanium and zirconium oxyhydrates have been prepared using various additives and synthesis procedures, and the heating kinetics of polyacids and the mechanism of nanoparticle agglomeration during the thermolysis process have been studied. The resultant m
- Shveikin,Nikolaenko
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p. 510 - 516
(2010/09/17)
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- Catalytic material and method of production thereof
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The present invention features a catalytic material which includes a metal catalyst anchored to a nano-sized crystal containing a metal oxide. Furthermore, the present invention features a method of producing the catalytic material described herein. Finally, the present invention features using the catalytic material for removing contaminants and for getting the desired products.
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Page/Page column 10-11
(2009/06/27)
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- MATERIAL, ITEM AND PRODUCTS COMPRISING A COMPOSITION HAVING ANTI-MICROBIAL PROPERTIES
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A coating product comprises a composition having the general formula AOx- (L-Men+)i, wherein AOx is a metal or metalloid oxide in which x indicates the number of the Oxygen atom(s) (O) bonded to the metal (A) atom, Men+ is a metal ion, L is a bifunctional molecule that could bind both metal oxide or metalloid oxide (AOx) and the metal ion (Men+), and i is the number of (L-Men+) groups bound to the metal oxide AOx; the value of the parameter i depending on various factors, such as the size of the nanoparticle of AOx, the nature of the, molecule L.
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Page/Page column 29
(2008/06/13)
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- Infrared spectra and structures for Group 4 dihydroxide and tetrahydroxide molecules
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Hafnium and zirconium atoms react with H2O2 molecules and with H2 + O2 mixtures to form M(OH) 2 and M(OH)4 molecules, which are trapped in solid argon and identified from isotopic shifts in
- Wang, Xuefeng,Andrews, Lester
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p. 10689 - 10701
(2008/10/09)
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