Pt-doped TiO2 Research Articles

Apparatus for the investigation of high-temperature, high-pressure gas-phase heterogeneous catalytic and photo-catalytic materials.

A high-temperature, high-pressure, pulsed-gas sampling and detection system has been developed for testing new catalytic and photocatalytic materials for the production of solar fuels. The reactor is fitted with a sapphire window to allow the irradiation of photocatalytic samples from a lamp or solar simulator light source. The reactor has a volume of only 3.80 ml allowing for the investigation of very small quantities of a catalytic material, down to 1 mg. The stainless steel construction allows the cell to be heated to 350 °C and can withstand pressures up to 27 bar, limited only by the sapphire window. High-pressure sampling is made possible by a computer controlled pulsed valve that delivers precise gas flow, enabling catalytic reactions to be monitored across a wide range of pressures. A residual gas analyser mass spectrometer forms a part of the detection system, which is able to provide a rapid, real-time analysis of the gas composition within the photocatalytic reaction chamber. This apparatus is ideal for investigating a number of industrially relevant reactions including photocatalytic water splitting and CO2 reduction. Initial catalytic results using Pt-doped and Ru nanoparticle-doped TiO2 as benchmark experiments are presented.

Effect of Pt Concentration on the Grain Growth of TiO2sol-gel Films

Pt metallic has been supported on TiO2 surface using different methods, Here, Pt doped TiO2 (Pt-TiO2) sol gel thin film were successfully produced by reducing chloroplatinc acid (H2PtCl6). The structures of prepared composites were investigated using X-ray diffraction (XRD). The physical morphologies of the composites were examined using transmission electron microscope (TEM). The grain size of Pt-TiO2 thin film after annealing was also measured by atomic force microscope (AFM) images.

Hydrogen production by photocatalytic water-splitting on Pt-doped TiO2–ZnO under visible light

Abstract Pt/TiO 2 –ZnO photocatalytic materials were prepared for the generation of hydrogen gas from water splitting. The photocatalysts were characterized by X-ray diffraction (XRD), UV-visible spectra (UV–Vis), scanning electron microscope (SEM) and transmission electron microscope (TEM). The absorption wavelength of TiO 2 was shifted to longer wavelength on Pt/TiO 2 –ZnO. A 400 W mercury arc lamp with a cutoff filter which filter out all the wavelengths under 400 nm as the visible light source. It reached up to the optimum value of 203 µmolh −1 g −1 on TiO 2 –ZnO (Ti/Zn = 10). A catalyst of 0.5 wt% Pt/TiO 2 –ZnO (Ti/Zn = 10) was used and a best hydrogen production rate through water splitting was reaching to 2150 µmolh −1 g −1 . The 0.1 wt% Pt/TiO 2 –ZnO showed a satisfying long-term stability, and 88% and 77% of initial hydrogen productivity still remained after 7 days and 14 days, respectively.

Efficient hydrogen production by photocatalytic water-splitting using Pt-doped TiO2 hollow spheres under visible light

Pt doped TiO2 hollow spheres (Pt/HS-TiO2) are prepared by a sol–gel method and characterized by XRD, SEM, TEM and UV-visible absorption spectra. In addition, Pt/HS-TiO2 is employed as the catalyst for photocatalytic hydrogen production from water splitting under visible light irradiation. The results show that Pt/HS-TiO2 with hollow sphere structure presents excellent photocatalytic hydrogen evolution performance. The hydrogen generation rate can reach more than 1023.71μmolh−1g−1 at room temperature and no obvious deactivation is observed after 30h irradiation. Furthermore, the reactively of Pt/HS-TiO2 could be reproduced in the repeated cycle. Therefore, Pt/HS-TiO2 is a promising photocatalyst to efficiently generate hydrogen under visible-light irradiation at room temperature.

Pt–TiO2-assisted photocatalytic degradation of the cytostatic drugs ifosfamide and cyclophosphamide under artificial sunlight

The aim of this work was to develop an effective photocatalytic technique for the removal of two cytostatic drugs from water. To this end, the kinetics, efficiency and decomposition pathway of the photocatalytic decay of ifosfamide (IF) and cyclophosphamide (CF) was investigated. The samples of Pt-doped (0.15at.%) and undoped TiO2 photocatalysts were prepared by a simple sol–gel method and then structurally characterized. The effects of operating parameters such as loading of photocatalyst, drug concentration, and photoactivity in solar and visible light were studied. The degradation processes in both drugs followed a pseudo-first-order kinetics. A degradation mechanism was proposed based on the identification of inorganic intermediates (NH4+, Cl−, PO43−) and organic by-products. The results showed that PO43− ions released during the decomposition of drugs were adsorbed on the photocatalyst, but this phenomenon had no negative effect on its photoactivity. The experimental results of the reactive species quenching showed that OH radicals were the predominant oxidant species participated in reaction, and the oxidation of drugs occurred in the bulk solution. Moreover, Pt-doped TiO2 was more effective at generating OH radicals than TiO2, probably due to the significantly promoted electron/hole separation in the modified photocatalyst. The results also demonstrated that the decomposition pathways of IF and CF differed.

Enhanced photocatalytic activity of Pt-doped TiO2 for NOx oxidation both under UV and visible light irradiation: A synergistic effect of lattice Pt4+ and surface PtO

Various platinum doped TiO2 with different doping ratios was successfully synthesized by a facile sol–gel method. The structural and optical properties of as-synthesized samples were characterized by the X-ray diffraction (XRD), high resolution transmission electron microscopy (HRTEM) and UV–vis diffuse reflectance spectroscopy (DRS). The results showed that all samples were anatase crystals and showed extended absorption into visible light region. The Pt states in the samples were investigated by energy dispersive spectrometer (EDS) and X-ray photoelectron spectra (XPS) analyses. The results revealed that Pt4+ ions were doped into TiO2 crystal lattice with a part of PtO deposited on the TiO2 surface. Pt doped TiO2 exhibited a significantly enhanced activity than pure TiO2 and P25 for the photocatalytic oxidation of NOx under irradiation of UV light, simulate sunlight and visible light. An obviously suppressed recombination rate of photo-generated carriers in the Pt doped TiO2 was demonstrated by photoluminescence (PL) spectroscopy measurements. These results suggested that the synergistic effect of two Pt species coexisted in the catalysts played an important role in the improvement of photocatalytic performance. The photocatalytic reaction mechanisms of NOx oxidation on the catalyst under UV and visible light irradiation were discussed in detail.

Green synthesis of Pt-doped TiO2 nanocrystals with exposed (001) facets and mesoscopic void space for photo-splitting of water under solar irradiation.

We report a non-trivial facile chemical approach using ionic liquid ([bmim][Cl]) as a porogen for the synthesis of (001) faceted TiO2 nanocrystals having mesoscopic void space. This faceted TiO2 nanomaterial has been doped with Pt nanoclusters through chemical impregnation. The resulting Pt-doped TiO2 nanomaterials are thoroughly characterized by powder X-ray diffraction (PXRD), Raman spectroscopy, field emission scanning electron microscopy (FE-SEM), ultra high resolution transmission electron microscopy (UHR-TEM), energy dispersive X-ray spectrometry (EDX), UV-vis diffuse reflection spectroscopy (DRS) and N2 sorption studies. These Pt/TiO2 nanocrystals with (001) exposed facets are employed as efficient and benign catalysts for hydrogen production from pure water and methanol-water systems under one AM 1.5G sunlight illumination. The effect of platinum loading and methanol-water ratio on the photocatalytic activity of the faceted TiO2 nanocrystals are investigated and it is found that hydrogen evolution rates have been enhanced significantly upon Pt loading. Under optimized reaction conditions the highest photocatalytic activity of 11.2 mmol h(-1) g(-1) has been achieved over ca. 1.0 wt% Pt loaded Pt/TiO2 nanocrystals with (001) exposed facets, which is one of the highest hydrogen evolution rates over the noble metal/TiO2 system reported to date in the literature.

A simple process for synthesizing nano Pt- and/or N-doped titanium dioxide powders by microwave plasma torch

Simultaneous N- and Pt-doped TiO2 powders are usually synthesized via multi-stage processes. In this study, Pt/N-doped (sample Pt/N-TiO2), Pt-doped (sample Pt-TiO2), N-doped (sample N-TiO2), and without doping (sample TiO2) TiO2 in the form of spherical nano to micro-particles are rapidly synthesized in a single-step process by spraying clear Ti- and Pt-containing nano aerosols into an atmospheric-pressure microwave plasma torch. The anatase modified Pt/N-TiO2 powders were produced in about 0.12s. After the collection of 14-stage impactors, the size distribution showed that the most of the particles by number were in the <10nm stage impactor, reaching 95.21%, 96.94%, and 97.94% of the total particle numbers for N-TiO2, Pt-TiO2, and Pt/N-TiO2 powders, respectively, although the mass distribution of the powders was mainly in the 1–2.5μm range. Chemical composition analysis showed that the N doped contents were 0.47, 0.21, and 0.41at.% in the N-TiO2, Pt-TiO2, and Pt/N-TiO2 powders, respectively, levels higher than that of the TiO2 sample (0.12at.%). As a result, the photocatalytic activities of N-containing (N-TiO2 and Pt/N-TiO2 samples) powders are significantly higher than those of TiO2 and P25 under visible light degradation. The rapid production of N- and/or Pt-TiO2 powders by using a simple plasma process can thus be achieved successfully for use in photocatalytic applications.

Nanocrystalline Pt-doped TiO2 thin films prepared by spray pyrolysis for hydrogen gas detection

Nanostructured pure and Pt-doped TiO2 thin films were prepared by chemical spray pyrolysis technique. Aqueous solution of TiCl3·6H2O (0·01 M) was chosen as the starting solution for the preparation of pure TiO2 thin film. Aqueous solutions of PtCl6·6H2O (0·01 M) and TiCl3·6H2O (0·01 M) were mixed in volume % of 1 : 99, 2·5 : 97·5 and 5 : 95 respectively to obtain Pt-doped TiO2 thin films. The solutions were sprayed onto quartz substrate heated at 350 °C temperature to obtain the films. These thin films were fired for one hour at 550 °C. The sensing performance of these films was tested for various gases such as LPG, H2, CO2, ethanol, NH3 and Cl2 (1000 ppm). The Pt-doped TiO2 (1 : 99) was observed to be most sensitive (572) to H2 at 400 °C with high selectivity against other gases. Its response time was short (10 s) and recovery was also fast (14 s). To understand the reasons behind the gas-sensing performance of the films, their structural and microstructral properties were studied using X-ray diffraction and electron microscopy (FE–SEM and TEM), respectively. Thicknesses of all these samples were determined using Surface Profiler. The results are interpreted.

Optimization of Conditions for the Photocatalytic Degradation of EDTA in Aqueous Solution with Fe-Doped Titanium Dioxide

The conditions for photocatalytic degradation of ethylenediaminetetraacetic acid (EDTA) in aqueous solution with Fe-doped titanium dioxide (TiO2) were optimized. The degradation efficiencies with Fe-doped TiO2 were better, compared with those obtained with bare TiO2 and Pt-doped TiO2. The effect of various experimental factors, such as photocatalytic dosage, temperature, solution pH and light intensity on the photocatalytic degradation of EDTA by Fe-doped TiO2 was investigated. The photocatalytic degradation treatment for the wastewater containing EDTA is simple, easy handling and low cost.

A Pt-Doped TiO2 Nanotube Arrays Sensor for Detecting SF6 Decomposition Products

The detection of partial discharge and analysis of SF6 gas components in gas-insulated switchgear (GIS) is important for the diagnosis and operating state assessment of power equipment. The use of a Pt-doped TiO2 nanotube arrays sensor for detecting sulfur hexafluoride (SF6) decomposition products is proposed in this paper. The electrochemical pulse deposition method is employed to prepare the sensor array. The sensor's response to the main characteristic gaseous decomposition products of SF6 is evaluated. The gas sensing characteristic curves of the Pt-doped TiO2 nanotube sensor and intrinsic TiO2 nanotube arrays sensor are compared. The mechanism of the sensitive response is discussed. Test results showed that the Pt-doped nanoparticles not only change the gas sensing selectivity of the TiO2 nanotube arrays sensor with respect to the main characteristic SF6 decomposition products, but also reduce the operating temperature of the sensor.

Heterogeneous photocatalytic treatment of pharmaceutical micropollutants: Effects of wastewater effluent matrix and catalyst modifications

This study evaluates the applicability of TiO2-based photocatalysts for the treatment of pharmaceutical micropollutants in secondary wastewater effluent (SWE). Photolytic experiments using SWEs with different compositions demonstrated that the rates of photocatalytic degradation of acetaminophen and carbamazepine inversely correlated with the concentration of dissolved organic carbon (DOC), regardless of the type of applied light source and initial pharmaceutical concentration. The critical relevance of organic matter to the scavenging behavior of SWE was further verified by assessing the photocatalytic performance as a function of the concentrations of potential effluent-derived quenchers (i.e., NO3−, Cl−, alkalinity, and humic acid). Kinetic comparison of the degradation of trace levels of pharmaceuticals (i.e., caffeine, cimetidine, propranolol, and sulfamethoxazole) using TiO2/UV-A, TiO2/UV-C, and H2O2/UV-C systems revealed that heterogeneous processes showed more significant performance reduction with increasing DOC concentration; this result indicates that organic matter plays dual roles in the scavenging activity of an effluent matrix: (1) OH radical (OH) quenching and (2) active-site coverage. TiO2 surface modifications (i.e., Pt and SiOx loading) accelerated the degradation of all the tested pharmaceuticals in SWEs to a certain degree. Particularly, the relevant altered surface affinity preferentially increased the susceptibility of specific pharmaceuticals to photocatalytic treatment. The presence of the effluent matrix substantially impaired the performance of visible-light-active photocatalysts in most cases. However, photocatalytic pharmaceutical degradation on Pt-doped TiO2, which occurs via direct charge transfer, was much less hindered in SWEs than that on Pt-deposited WO3, which occurs via OH-mediated oxidation.

Electronic structure, photocatalytic properties and phonon dispersions of X-doped (X = N, B and Pt) rutile TiO2 from density functional theory

First principles calculations were performed on the electronic, vibrational and Raman spectra of substitutional N-, B- and Pt-doped rutile titanium dioxide (TiO2), within the density functional theory (DFT), using the plane-wave pseudopotential method. From the calculated electronic band structure and density of states we concluded that the doping induces significant changes in the band structure of TiO2, highlighting B- and Pt-doped TiO2 as the best candidates for photocatalytic materials for visible light absorption. On the other hand, N-doped TiO2 appears to be active only for the photoreduction processes, although N doping introduces midstates into the band gap. Only N-doped TiO2 proved to have stable phonon dispersions and showed interesting band doubling.

Influences of pH value in deposition-precipitation synthesis process on Pt-doped TiO2 catalysts for photocatalytic oxidation of NO

This work has been undertaken to study the influences of pH value on the characteristics and activity of photocatalyst by deposition-precipitation method during its preparation process. A series of Pt-modified TiO2 were prepared by deposition-precipitation method at different pH values as well as wet impregnation method, and characterized by XRD, XPS, TEM, UV-Vis and photoluminescence (PL). It was found that the catalysts had the highest photocatalytic activity for NO conversion when pH value was kept at around 7. And the sample prepared by deposition-precipitation method showed higher activity than that by impregnation method. This was mainly due to their high value in highly-dispersed platinum oxides (PtOx) content on the surface of the catalysts. The results from UV-Vis absorption showed that highest absorbance was obtained for Pt/TiO2 prepared at pH values of around 7. And PL spectra results indicated that the recombination rate of photogenerated electrons and holes of the samples prepared by deposition-precipitation method was lower than that prepared by impregnation method. And in the zeta potential study, the pH values for the isoelectric point of the preparing slurry of 0.05 wt.%Pt/TiO2 and 0.5 wt.%Pt/TiO2 were determined to be 6.5−8.5, which further confirmed the enrichment of PtOx dopants for the catalysts repapered when pH value was around 7.

Disinfection of water using Pt- and Ag-doped TiO2 photocatalysts

In this article we have reported heterogeneous photocatalytic disinfection using pristine and Ag- and Pt-doped nano TiO2 under near-UV light and solar light irradiation. Disinfection experiments were conducted in slurry reactors with Escherichia coli, artificial light and sunlight. The influence of various amounts of Pt and Ag loading (0.5% to 5%) on the E. coli inactivation was examined and results indicated that 5% Pt-TiO2 and 0.5% Ag-TiO2 showed the highest photocatalytic E. coli inactivation. The Pt- and Ag-doped photocatalysts were characterized using XPS and TEM analysis. The influence of experimental parameters such as various photocatalysts, photocatalyst concentration, reactor geometry effect, pH and temperature on the photocatalytic disinfection was studied. The experimental results show that sunlight or near-UV light with TiO2 photocatalyst strongly inactivates E.coli. The Ag-TiO2 photocatalyst was the most efficient photocatalyst tested for bactericidal activity. A plausible mechanism of photocatalysed E. coli inactivation is discussed. In conclusion, the doped nano TiO2 photocatalysts is a potential candidate for E. coli inactivation.

Pentose Acting as a Sacrificial Multielectron Source in Photocatalytic Hydrogen Evolution from Water by Pt-doped TiO2

Abstract Photocatalytic reaction was performed by irradiation of Pt-doped TiO2 in an aqueous solution of xylose acting as a sacrificial reagent to evolve hydrogen, whose amounts reached 8.6 equivalents to the xylose used.

The effect of infrared light on visible light photocatalytic activity: An intensive contrast between Pt-doped TiO2 and N-doped TiO2

Pt-doped TiO2 and N-doped TiO2 were prepared, using nanotubular titanic acid as precursor, by wet impregnation and NH3-heating method, respectively. Both Pt-doped and N-doped TiO2 show an apparent photocatalytic oxidation of propylene under visible light irradiation. The origin of visible light sensitization was ascribed to the intra-band contributed by the formation of single-electron-trapped oxygen vacancies, while dopants platinum or nitrogen play a role not only in suppressing the recombination of photoinduced electrons and holes but also in increasing the ability of visible light absorption of TiO2. The visible light photocatalytic activity of Pt-doped TiO2 can be greatly improved by additional infrared light irradiation, while visible-light-active N-doped TiO2 has no such phenomenon. Infrared light per se is unable to excite Pt-doped TiO2 catalyst to initiate photocatalytic reaction, but the strong interaction between platinum and oxygen vacancies resulted in absorption peaks at 800–900nm, resulting in a giant enhancement in visible light photocatalytic activity of Pt-doped TiO2 in the presence of infrared light irradiation because the formed heterojunctions between dopants Pt and TiO2 may function as thermal catalytic sites. The influences of reaction temperatures on visible light photoactivity of both Pt-doped and N-doped TiO2 were studied. It was found that both C3H6 removal and CO2 selectivity over Pt-doped TiO2 were increased with increasing the reaction temperature, while it was inert for N-doped TiO2.

Photocatalytic Activities of Transition Metal-Doped TiO&lt;sub&gt;2&lt;/sub&gt; Nano-Powders by Sonochemical Method and their Physicochemical Properties

With respect to metal doping into TiO2, the doping limits for V, Cr, Zr, Nb, Mo, and W are predicted to be higher than other transition metals according to the binding energy calculations in a unit cell model of anatase TiO2, which suggests that Cr and W can be doped into anatase structure more easily than Ag or Pt, for example. Our investigation has twofold research objectives. One is to prepare metal-doped TiO2 nano-powders from these transition metals, and the other is to test photocatalytic activity of each resulting powder. For the former, sonochemical process has been used to produce Cr-doped, W-doped, Ag-doped, and Pt-doped TiO2 nanoparticles. For the latter, we have performed photocatalytic oxidation of methylene blue. The combined results of the morphology and photocatalytic activites have enabled characterization of the physicochemical properties of these transition metal-doped nanoparticles.

Effect of structure on the photocatalytic activity of Pt-doped TiO2 nanotubes

Highly ordered TiO2 nanotubes with different tube length were fabricated by anodization using C2H2O4·2H2O containing 0.5wt.% NH4F (electrolyte A) and anhydrous dimethyl sulfoxide containing 1% HF (electrolyte B), respectively. Then cathodic reduction method was used to dope Pt in TiO2 nanotubes in chloroplatinic acid. The results indicated that cathodic reduction could efficiently platinize TiO2 nanotubes. Pt-doped TiO2 nanotubes with the longer length had the higher photocatalytic activity for degrading methyl orange under UV and visible irradiation. The longer tube length has a positive effect on the photocatalytic activity of Pt-doped TiO2 nanotubes. Besides, as the content of anatase further decreases, the photocatalytic activity drops gradually due to the reduction reaction in the surface area.

Photocatalytic Degradation of Diazinon by Pt-doped TiO2

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