Y-doped TiO2 Research Articles

Effect of Yttrium doping on enhancing the photocatalytic performance of TiO2/GO nanocomposite

Pure and Yttrium doped Titania/Graphene oxide (YTGO) nanocomposites were synthesized by hydrothermal method. XRD analysis confirmed the crystal structure and anatase phase of TiO2 nanoparticles. The anatase phase of TiO2 has been retained in the composite as confirmed from the XRD pattern. SEM and TEM images revealed that the spherical TiO2 nanoparticles are embedded into sheet like structures of GO. The size of the spherical nanoparticles in the composites is relatively smaller than that of pure sample due to anchoring on the GO sheets. The photocatalytic performance of TiO2 has significantly increased in the Y-doped TiO2 with GO compared to pure TiO2 and TiO2/GO (TGO). Moreover, 0.7 % Y-doped TiO2/GO nanocomposite exhibited superior photocatalytic performance with overall efficiency of 97 % compared to other samples. The 0.7 % Y-doped TiO2/GO nanocomposite shows higher rate constant and shorter half life time compared to other samples. The enhancement of photocatalytic activity of YTGO composites attributed to the combination of increased absorption due to the absorption edge shift and effective separation of photo generated carriers.

Effect of yttrium on catalytic performance of Y-doped TiO2 catalysts for propane dehydrogenation

Defective bulk catalysts based on TiO2 have superior catalytic performance for propane dehydrogenation (PDH). The oxygen vacancy concentration and the number of active sites on the catalyst surface can be effectively tuned by doping metal in TiO2. Herein, yttrium (Y)-doped titanium dioxide (nY/TiOx) catalysts were in-situ synthesized via the coprecipitation method to study the effect of rare earth metal Y doping on the structure of TiO2 and the catalytic performance for PDH. Experimental results demonstrate that Y-doped TiO2 exhibits higher catalytic activity, propylene selectivity and stability than bare TiO2. Full characterizations with X-ray diffraction (XRD), high-resolution transmission electron microscope (HRTEM), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy of pyridine adsorption (Py-IR), temperature-programmed desorption of ammonia (NH3-TPD), H2 temperature-programmed reduction (H2-TPR), and Raman techniques on these catalysts reveal that Y3+ can enter TiO2 lattice, and the lattice stability of the catalyst can be enhanced by replacing Ti4+ to form Y–O–Ti structure. Meanwhile, the introduction of an appropriate amount of Y can obviously promote the PDH reaction by adjusting the acidity of the catalyst, improving the release capacity of TiO2 lattice oxygen and increasing the formation of active centers. Nevertheless, excessive Y doping will lead to pore clogging, and the exposure of active sites will be reduced, resulting in the degradation of catalytic performance.

Effect of Y-doped TiO2(B)/SnO2 1D structured nanocomposite on the performance and capacity of lithium-ion batteries

Because traditional graphite anode for Lithium-ion batteries (LIBs) has low coulombic efficiency, high irreversible capacity and large volume expansion which can no longer satisfy the requirements of high-performance batteries. This article therefore presented the development of an anode material based on structural design to enhance its properties. One-dimension structured nanocomposites of yttrium-doped TiO2(B) nanowires/ SnO2 nanotubes were synthesised at various yttrium concentrations via hydrothermal method. Phase composition, crystal structure, morphologies, and electrochemical properties were evaluated to study the effects of the dopant on performance and capacity of the LIBs. XRD showed the modification in crystalline size and lattice parameters when yttrium was introduced. Electrochemical properties were markedly enhanced by the yttrium-doped nanocomposites, especially for the one with 0.5%mole yttrium (TSY50). The TSY50 offered the highest diffusion coefficient of 2.34×10-10 cm2 /s, reduced the Li-ion diffusion length and the cell resistance, improved the specific capacity, cycle performance and capacity retention, as demonstrated by cycling tests. The prepared yttrium-doped nanocomposite could be considered as a promising material for its application as an anode in LIBs.

Optical absorption of tri-doped (Mo, Y, N)-TiO2 with first-principle calculations

In this theoretical study, a path was adapted to investigate the redshifting of the TiO2 absorption edge by molybdenum (Mo), yttrium (Y) and nitrogen (N) doping. The geometrical model, band gap and photo response were noted in the developed model of anatase TiO2. The tri-doped model showed very small modification in the structure as compared to a reference TiO2 model. The 3d states of Mo mix up with the 3d states of Ti, resulting in the reduction of band gap. The Y 2p states were introduced around the middle of the band gap of Y-doped TiO2. Good reduction was found in the gap of tri-doped TiO2 model and the created states were occupied. The doping of N via oxygen (O) substitution in tri-doped model resulted in the band gap reduction by introducing states in the band gap due to the mixing of N 2p and O 2p states.

Hydrogen Assisted Magnesiothermic Reduction of Y-Doped, Nanocrystalline TiO2

The direct reduction of TiO2 to low-oxygen titanium metal is achievable via Hydrogen Assisted Magnesiothermic Reduction (HAMR). To investigate and leverage the oxygen-scavenging properties of rare-earth dopant species on the HAMR process, Y-doped and undoped TiO2 powders were synthesized and characterized. HAMR blends incorporating the synthesized TiO2 were reduced under forming gas atmospheres. X-ray powder diffraction (XRD) and scanning electron microscope (SEM) characterization was performed prior to and following reduction. The TiO2 powders were observed to be dense and nanocrystalline. Following reduction, more extensive development of intermediate HAMR phases was observed as a result of Y-doping. The microstructure/phase evolution of the HAMR reduction phases was observed to deviate from the expected for dense TiO2 particles. Rapid restructuring of the TiO2 particle interiors was attributed to increased bulk diffusion rates of nanocrystalline materials. Doped nanocrystalline TiO2 powders were identified as potential alternative feedstocks for HAMR experiments. The byproduct MgO phase was observed to grow as a particle agglomerating network that is dense when formed at 750 °C and porous when formed at 900 °C.

Comparison of high-k Y2O3/TiO2 bilayer and Y-doped TiO2 thin films on Ge substrate

Y2O3/TiO2 bilayer thin films and Y-doped TiO2 (YTO) thin films were deposited on a Ge substrate by atomic layer deposition at a substrate temperature of 250 °C. They were used as gate insulators to examine the electrical properties of Pt/TiN/TiO2/Y2O3/p-Ge and Pt/TiN/YTO/p-Ge metal–oxide–semiconductor capacitors. A 7 nm thick bilayer thin film showed a lower leakage current density by more than one order of magnitude compared to a YTO thin film with the same thickness due to the high conduction band offset between the Y2O3 layer and Ge substrate. However, the bilayer thin film showed a large hysteresis of 950 mV. On the other hand, the YTO thin film showed significantly reduced hysteresis of 120 mV due to the smaller slow trap density. The voltage acceleration factors of the bilayer thin film and YTO thin film were 1.12 and 1.25, respectively, higher in the YTO thin film. The interfacial trap density of the 7 nm thick bilayer and YTO thin films were 3.5 × 1011 cm−2 eV−1 and 2.7 × 1011cm−2 eV−1, respectively. The equivalent oxide thickness of the YTO film could be scaled down to 0.9 nm, and a leakage current density of 1.4 × 10−4A cm−2 at flat band voltage −1 V was achieved. This study confirmed that the YTO film can be used as a promising ternary high-k oxide for a Ge-based field-effect-transistor.

Y-doped TiO2 coating with superior bioactivity and antibacterial property prepared via plasma electrolytic oxidation

To improve the bioactivity and antibacterial properties of implant materials. In this study, the biomedical titanium alloy (Ti-6Al-4V) was covered by yttrium doped titanium dioxide (Y-TiO2) coating via a plasma electrolytic oxidation (PEO) method. By changing the concentration of yttrium acetate in the electrolyte, Y-TiO2 coating with different mass ratios of yttrium were obtained. The structure morphology and chemical composition of the Y-TiO2 coating were systematically characterized. The results indicated that the porous and micro-nanostructured Y-TiO2 coatings were constructed by the pores smaller than 4 μm. Definitely yttrium was not only distributed on the surface but also embedded in the coating. Yttrium mainly existed in form of Y2O3 and Y3+ state in prepared TiO2 coating. Element release profiles confirmed that yttrium release slowly from Y-TiO2 for 32 days. Cell culture tests demonstrated that Y-TiO2 coating exhibited good biocompatibility on osteoblastic precursor cells and fibroblasts cells with increasing doping concentration of yttrium. Bacteriostasis experiments revealed that Y-TiO2 coating possess excellent antibacterial property against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). Thus, the prepared Y-TiO2 coating with outstanding biocompatibility and antibacterial capacity provided a preferred strategy for the repair and reconstruction of bone tissues in dentistry and orthopedics.

Enhanced electronic transport in Y-doped TiO2 branched nanorod array thin film electrodes

A series of Y-doped TiO2 branched nanorod arrays with different Y content were synthesized by hydrothermal approach. Incorporation of Y3+ into the rutile TiO2 lattice was confirmed by x-ray photoelectron spectroscopy measurement. The effect of Y dopant on the morphology, structure, optical properties and photoelectrochemical performance of TiO2 branched nanorod array thin films was investigated by x-ray diffraction, field-emission scanning electron microscopy, UV–vis spectroscopy, photoluminescence spectroscopy and electrochemical workstation. The length of TiO2 branched nanorod arrays varied with the amount of Y dopant. Y-doped TiO2 exhibited the enhanced visible-light absorption ability and the reduced optical band gap energy compared with the pure TiO2. It was found that TiO2 branched nanorod array thin film electrode with Y/Ti molar ratio of 3% possessed the optimal electron transport behavior, which can be ascribed to the enhancement of visible-light utilization efficiency, the narrowest band gap energy, the lowest charge recombination rate and the highest photo-excited electron yield.

Yttrium-doped TiO2 compact layers for efficient perovskite solar cells

To improve the electron transporting and suppress the charge recombination at the interface of TiO2/perovskite, the smooth and compact yttrium(Y)-doped TiO2 compact layers were successfully prepared via a hydrolysis-pyrolysis method. The influences of Y-doped on the microstructure, crystal phase, chemical composition, optical absorption of the TiO2 compact layers were investigated, and the electron transporting and charge recombination at the TiO2/perovskite interface of solar cells were systemically analyzed. The planar perovskite solar cells based on the Y-doped TiO2 compact layers with a Y/Ti molar ratio of 5% obtained a best photoelectric conversion efficiency (PCE) of 15.52%, comparing with a PCE of 14.05% from the undoped devices. When the 200-nm length 3% Y-doped TiO2 nanorod arrays were introduced between the 5% Y-doped TiO2 compact layers and the perovskite thin film, the champion cell achieved a PCE of 18.32% under illumination of simulated AM 1.5 sunlight (100 mA cm−2).

Synthesis, Morphological Analysis and Photovoltaic Performance of Thallium- and Yttrium-Doped Titanium Dioxide-Based Dye-Sensitized Solar Cells

Thallium (Tl) and yttrium (Y) have been doped separately, as an extrinsic impurity, into titania (TiO2) matrix to investigate the effect of dopant ion on the photovoltaic properties of the resultant dye-sensitized solar cells (DSCs). The metals were selected on the basis of their electrical conductivities. Two types of DSCs were fabricated: the first type with a single semiconductor layer of either pure TiO2 or Tl- or Y-doped TIO2, and the second type was of double-layered cells having a nanocrystalline TiO2 foundation layer and above it mesoporous TiO2 (pure or doped) as a scattering layer. X-ray diffraction and scanning electron microscopy analyses revealed the formation of composite-like Tl4O3 structures in an anatase matrix of annealed Tl-doped titania, whereas Y limited the nucleation and growth process and resulted in smaller particles. UV–visible and photoluminescence spectroscopies showed obvious improvement in the optical properties of TiO2 with Tl doping, whereas Y adversely affected the film characteristics. The resultant photo-anodes in DSCs under 100 mW cm−2 light illumination gave a photovoltaic conversion efficiency of 1.07% for pure TiO2, while Y-doped and Tl-doped TiO2 showed 0.36% and 3.63% efficiency, respectively. The findings were ascribed mainly to the relative electrical conductivities and partially to the morphological structures of the doped samples.

Yttrium-doped TiO2 nanorod arrays and application in perovskite solar cells for enhanced photocurrent density

Crystalline yttrium-doped rutile TiO2 nanorod arrays were synthesized and successfully implemented as a photoanode of perovskite solar cells. Study shows that yttrium was successfully doped and TiO2 band gap changes from 3.07 eV to 3.02 eV. A positive shift of 100 mV in the flat-band potential (Vfb) was observed in Y-doped rutile TiO2 nanorods. A power conversion efficiency of 7.95% and a photocurrent density of 15.13 mA/cm2 were obtained for the doped sample. The photocurrent density is 1.47 times higher than that of the un-doped device. Incident photon-to-current conversion efficiency shows Y-doped device has a clear increase in quantum efficiency in the visible light range from 450 and 750 nm. Open circuit voltage decay measurements demonstrate the superior ability of Y-doped TiO2 nanorod for separating electrons and holes and decreasing the recombination events. The improved performance is possibly attributed to the enhanced electron injection and transfer efficiency caused by a positive shift in Vfb and a reduction in charge recombination. This study opens a door toward the improvement of photocurrent density of perovskite solar cell via an element doping route.

Effect of Y and Mn doping into rutile type TiO2/Ge stack structure by combinatorial synthesis

The effects of Y and Mn doping into the rutile TiO2 films on a (100) Ge substrate stack structure were investigated by combinatorial synthesis. Composition spread films were fabricated by combinatorial pulsed laser deposition. Regardless of the dopant concentration, the Mn-doped TiO2 film indicated an amorphous structure. In contrast, the Y-doped TiO2 film had a rutile-type crystal structure below an Y concentration of 11.0 at. %. The high Y concentration enhanced the amorphous structure and Ge diffusion into the TiO2 layer. Although both dopants reduced leakage currents, the effect of Y was greater than that of Mn. The post-deposition annealed Y-doped TiO2 indicated an improvement in the leakage current by three orders of magnitude and electron accumulation at a capacitor structure. The Y doping into TiO2 may provide beneficial effects of good interface control and effective dielectric material for Ge-based capacitors.

Low-Cost Y-Doped TiO2 Nanosheets Film with Highly Reactive {001} Facets from CRT Waste and Enhanced Photocatalytic Removal of Cr(VI) and Methyl Orange

In this paper, efficiency recovery of rare earth elements from cathode ray tubes (CRT) waste. Moreover, recycled yttrium was also served as raw material to produce a low-cost Y-doped TiO2 nanosheets film with exposed {001} facets. An etching/dissolution growth mechanism was postulated by systematically investigating the influence of the reaction time. The synergistic effect of the Y dopant and the dominant {001} facets endows TiO2 nanosheets film with excellent activity in the photoremoval of Methyl Orange (MO) and Cr(VI). A possible mechanism of photoremoval of MO and Cr(VI) is proposed. This study not only contributes to recycling methods for CRT waste but also presents a new way to prepare low-cost sustainable photocatalytic materials using economically viable waste.

Phase control of yttrium (Y)-doped TiO2 nanofibers and intensive visible photoluminescence

Yttrium (Y)-doped TiO2 nanofibers were successfully fabricated by electrospinning and the subsequent calcination of the as-spun nanofibers. The X-ray diffraction and Raman scattering results showed that the incorporation of Y into TiO2 impedes the rutile-phase growth, facilitates the anatase phase growth. Estimated grain sizes are reduced from 15.71nm to 8.8nm with increasing Y-doping concentration. Raman scattering studies confirm the existence of slight brookite phase in case of Y-doped TiO2 nanofibers. Field emission scanning electron microscope (FESEM) and transmission electron microscope (TEM) images revealed that the nanofibers comprised of nanoparticles and that Y-doping reduced the nanoparticle size. The optical band gap energy increased with increasing Y-doping, which can be ascribed to both quantum confinement effect and pure anatase phase transformation from mixed rutile-anatase phase. Y-doping induced a blue-shift of the broad visible photoluminescence (PL) peak and an increase of PL intensity with the concurrent decrease grain size. For 3at.% Y-doped TiO2 nanofibers PL intensity enormously increased due to defect-related centers on the surface.

Surface oxygen vacancies in gold based catalysts for CO oxidation

Experimental catalytic activity measurements, diffuse reflectance infrared Fourier spectroscopy, and density functional theory calculations are used to investigate the role and dynamics of surface oxygen vacancies in CO oxidation with O2 catalyzed by Au nanoparticles supported on a Y-doped TiO2 catalyst. Catalytic activity measurements show that the CO conversion is improved in a second cycle of reaction if the reactive flow is composed by CO and O2 (and inert) while if water is present in the flow, the catalyst shows a similar behaviour in two successive cycles. DRIFTS-MS studies indicate the occurrence of two simultaneous phenomena during the first cycle in dry conditions: the surface is dehydroxylated and a band at 2194 cm−1 increases (proportionally to the number of surface oxygen vacancies). Theoretical calculations were conducted in order to explain these observations. On one hand, the calculations show that there is a competition between gold nanoparticles and OH to occupy the surface oxygen vacancies and that the adsorption energy of gold on these sites increases as the surface is being dehydroxylated. On the other hand, these results evidence that a strong electronic transfer from the surface to the O2 molecule is produced after its adsorption on the Au/TiO2 perimeter interface (activation step), leaving the gold particle in a high oxidation state. This explains the appearance of a band at a wavenumber unusually high for the CO adsorbed on oxidized gold particles (2194 cm−1) when O2 is present in the reactive flow. These simultaneous phenomena indicate that a gold redispersion on the surface occurs under reactive flow in dry conditions generating small gold particles which are very active at low temperature. This fact is notably favoured by the presence of surface oxygen vacancies that improve the surface dynamics. The obtained results suggest that the reaction mechanism proceeds through the formation of a peroxo-like complex formed after the electronic transfer from the surface to the gas molecule.

Preparation of Y-doped TiO2 by hydrothermal method and investigation of its visible light photocatalytic activity by the degradation of methylene blue

Nano-sized yttrium (Y)-doped TiO2 with different Y doping concentrations has been synthesized by hydrothermal method. With pure anatase phase, the as-synthesized samples possess good crystallinity and spherical morphology with uniform particle size distribution. Y doping shifted the absorption edge of TiO2 towards visible light region, as observed from the UV–vis. absorption spectra. XPS (X-ray photoelectron spectroscopy) analysis indicates that Y3+ replaces lattice Ti4+ leading to substitutional point defects. The photocatalytic activity of the synthesized sample was evaluated by the degradation of methylene blue in aqueous solution under visible light irradiations. Y-doped TiO2 shows enhanced photocatalytic activity compared with that of bare TiO2. Compensated and non-compensated density functional theory based calculations were performed for reasonable explanation of the experimental findings. Compensated model with Y3+ replacing Ti4+ along with concomitant presence of an oxygen vacancy might explain the improved photocatalytic activity of Y-doped TiO2. The enhanced photoactivity of Y-doped TiO2 is assigned to the reduced band gap, enhanced visible light absorption and improved separation of electron–hole pairs.

Hydrophilic and Photocatalytic Performances of Y-Doped Titanium Dioxide Thin Films

Pure and Y-doped TiO2 thin films are prepared on glass by sol-gel method. Tetrabutyl titanate was used as Ti precursors. The chemical composition, structure and properties of TiO2 thin films are characterized by XRD, FT-IR, UV-Vis and Optical Contact Angle Measuring Instrument. Their photocatalytic performances were studied in detail by the methylene blue degradation model. The results show that the crystalline phase of Y2Ti2O7 is formed and the phase transformation from anatase to rutile is restrained when Y is doped in the TiO2 thin films. However, with the continuous increase in calcination temperature, its photocatalytic activity decreases, because the anatase will transform to the rutile. The proper amount of Y doping will cause the lattice to expand, the new defects will form and the smaller band-gap energy will be revealed. Thus, the absorption ability toward the ultraviolet can be improved, the redshift of the absorption band can also be found. As the results of it, the hydrophilicity and photocatalytic efficiency can improved. Furthermore, the photocatalytic activity increases with the hydrophilicity. When the calcination temperature of thin films is 450oC and the Y-doping is 0.3%, the main crystalline phase of the samples is the anatase, the contact angle is only 13.7o and the degradation ratio of methylene blue reached 98.84%.

Photocatalytic Activity of La, Y Co-Doped TiO<SUB>2</SUB> Nanoparticles Synthesized by Ultrasonic Assisted Sol–Gel Method

Bare TiO2 (T), La-doped TiO2 (LT), Y-doped TiO2 (YT), La, Y co-doped TiO2 (LYT) were successfully prepared by facile ultrasonic assisted sol-gel synthesis using Ti(OC4H9)4 as the precursor. The products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), UV-visible diffuse reflectance spectra (DRS), and X-ray photoelectron spectroscopy (XPS), respectively. The photocatalytic activities of anatase samples, with the average particle diameters ranging from 14 nm to 21 nm, were evaluated for photodegradation of methyl orange (MO). The XPS results indicated that Y atoms were incorporated into titania lattice, while La atoms existed on the crystal surface. Due to doping, the optical absorption edges of LT, YT, and LYT shifted to the visible light region by 21 nm, 29 nm and 35 nm, respectively. The photocatalytic performances of the doped samples, such as LT, YT and LYT, were much higher than that of bare TiO2 under UV-visible light irradiation. And the photoreactivity efficiency of the LYT was the highest. It indicated that a strong La-Y synergistic interaction appeared to play a decisive role in driving the excellent photocatalytic performance of titania.

The Impact of Y Addition into TiO2 on Electronic States and Resistive Switching Characteristics

We have studied electronic structures and resistive switching characteristics of Y-doped TiO2 films as a function of Y content to improve the performance on resistive switching of TiO2-based ReRAM. TiYxOy films with different Y contents were deposited on a Pt layer by metal organic chemical vapor deposition (MOCVD) using dipivaloymethanato (DPM) precursors and followed by O2 anneal to densify the films. A fairly good compositional uniformity in each TiYxOy film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The energy bandgap (Eg) of the TiYxOy films, which was determined by analyzing the absorption coefficient, was gradually increased with the Y content. Since a decrease in valence band offset between TiYxOy and Pt was almost the same as that in Eg, the conduction band offset was almost constant at ∼1.3 eV. The current–voltage (I–V) characteristics of TiYxOy films, which were measured by sweeping positive bias to a Au top electrode after forming process, show non-polar type resistive switching and its beneficial change with Y incorporation into the TiO2 matrix. The Y addition is quite effective to improve endurance in resistive switching and to reduce the variations of operation voltages (VSET and VRESET).

Preparation and characterization of cerium oxide doped TiO2 nanoparticles

A mixed oxide consisting of TiO2 as the major phase and CeO2−y (0<y<0.5) as the dopant phase was prepared via the sol-gel reaction of Ti(i-OC3H7)3 in an aqueous solution of Ce(NO3)3. The resulting oxide powders with different CeO2−y contents were all composed of nano-sized spheres. The CeO2−y phase was identified to have retarding effect on the phase transition from anatase TiO2 to rutile TiO2 at calcinations temperature as high as 800°C, which would otherwise be a thorough conversion. The CeO2−y–TiO2 powders could apparently shift the UV-absorption band of TiO2 toward visible range, and there was an optimal CeO2−y content in association with the maximum absorbance. This effect is interpreted as the existence of an n-type impurity band, due to the substitution of Ti4+ for Ce3+/4+ at the interface between the two oxides, in the gap of TiO2. According to X-ray photoelectron spectroscopy (XPS) investigation, the Ti element mainly existed as the chemical state of Ti4+ and the Ce oxide doping did not affect the peak position of Ti 2p. The Ce 3d spectrum of CeO2−y-doped TiO2 sample basically denotes a mixture of Ce3+/4+ oxidation states giving rise to a myriad of peaks.