TiO2-based Nanosheets Research Articles

Computational study of amyloid fibrils on interaction with TiO2-based nanotubes and nanosheets

Computational study of amyloid fibrils on interaction with TiO2-based nanotubes and nanosheets

One-pot synthesis of Fe2O3/Y2O3@TNS for enhanced photocatalytic and adsorption properties

TiO2-based nanosheets (TNS) modified with Fe2O3 and Y2O3 particles (Fe2O3/Y2O3@TNS), possessing a laminar structure with large specific surface area of 382 m2 g−1, were synthesized via a one-pot hydrothermal method.

Enhanced Photocatalytic Activity of Directly Assembled Fe₂O₃/Gd₂O₃@TiO₂-Based Nanosheets.

TiO₂-based nanosheets (TNSs) modified with surface-enriched Fe₂O₃ and Gd₂O₃ nanoparticles (NPs) have been synthesized via a direct interfacial assembly strategy. The TNSs with a unique two-dimensional structure are favorable for supporting Fe₂O₃ and Gd₂O₃ NPs for photocatalytic applications. The prepared samples were characterized using scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Raman spectroscopy (Raman), BET, X-ray photoelectron spectroscopy (XPS), UV-Vis diffuse reflectance spectra (DRS), photoluminescence (PL) spectroscopy and the surface photocurrent (SPC) technique. The photocatalysts exhibited large specific surface area (160-260 m²/g). The co-modification with Fe₂O₃ and Gd₂O₃ NPs influenced the crystallinity and surface area of the TNSs, and improved visible-light absorption. Surface photocurrent and PL studies revealed that the photogenerated charge carrier separation efficiency could be improved by an appropriate amount of NPs. The optimized nanostructure exhibited photocatalytic efficiency for rhodamine B (RhB) degradation and H₂ production is 5.66-fold and 2.99-fold respectively than those of TNSs under visible-light irradiation. The enhancement is attributed to the combined effect of Gd₂O₃ and Fe₂O₃ NPs in the Fe₂O₃/Gd₂O₃@TNSs composites. The simultaneous use of two different types of NPs led to a fast separation and slow recombination of photoinduced electron-hole pairs. A mechanism is proposed to explain the enhanced visible-light photocatalytic activity.

A facile one-pot hydrothermal synthesis of two-dimensional TiO2-based nanosheets loaded with surface-enriched NixOy nanoparticles for efficient visible-light-driven photocatalysis

Two-dimensional (2D) TiO2-based nanosheets (TNSs) decorated with surface-enriched NixOy (Ni = Ni2+, Ni3+) nanoparticles (Ni-TNSs) were synthesized and found to exhibit a high visible light photocatalytic activity. The thickness and high specific surface area of the Ni-TNSs were measured to be ∼5 nm and 280–350 cm2/g, respectively. Properties, such as the crystal structure, crystallinity, surface area and visible light absorption of the TNSs, were closely associated with the distributed nanoparticles of NixOy (The particle size is less than 2 nm) on the surface. Surface photocurrent, fluorescence spectroscopy, linear sweep voltammetry and Tafel measurements revealed that the separation efficiency of the photogenerated charge carriers can be improved by optimizing the concentration of NixOy (the optimized ratio of Ni/Ti = 3.0 at.%). The photocatalytic degradation of organic pollutants (RhB and MB) under visible light was measured, and the efficiency also strongly depended on the amount of NixOy nanoparticles with an optimal percentage of 3.0 at.%. The photoreactivity of the sample was further studied by determining the formation of photoinduced hydroxyl radicals (OH) by applying coumarin (COU) as a probe material and by obtaining ESR spectra of the superoxide radical adducts (O2−) trapped by DMPO (5,5-dimethyl-1-pyrroline n-oxide). Ten cyclic tests were used to confirm the high stability. A feasible mechanism is described to interpret the enhanced photocatalysis.

Facile synthesis of TiO2-based nanosheets by the regulation of cationic surfactants for effective adsorption-photocatalytic removal of high-chroma crystal violet

TiO2-based nanosheets (TNS) that possess higher specific surface area (∼6 times of that of P25) were synthesized using hydrothermal reaction assisted by cationic surfactant cetyltrimethylammonium Bromide (CTAB). The nanosheets exhibit larger size, higher photocurrent, and lower photoluminescence intensity. The adsorption test that includes Langmuir model suggests that the TNS synthesized by adding appropriate amount of CTAB (denoted as CT1-TNS) exhibit higher adsorption of crystal violet (CV) than that of TNS. The highest amount of CV adsorbed by monolayer (ηmax) of CT1-TNS (60.9 mg/g) is 1.24-fold of that of TNS (49.1 mg/g). The photoactivities of CT1-TNS in degrading CV and Rhodamine B (RhB) are 1.61 and 1.62-fold of that of TNS, respectively. The good reusability of CT1-TNS suggests their potential application for dealing with adsorption-photocatalytic degradation of dyes at high-concentration.

Visible-light-driven water splitting from dyeing wastewater using Pt surface-dispersed TiO2-based nanosheets

TiO2-nanosheet (TNS) was firstly fabricated using a one-pot hydrothermal route followed with photo depositing various dosages of Pt nanoparticles over its surface. The hydrogen production performance of these as-prepared samples was assessed in triehanolamine (TEOA) aqueous solutions under visible-light irradiation. The results showed the optimal ratio of Pt: TNS was 0.5 wt %, with apparent quantum efficiency (QE) climbing 15.44%. And on this basis, it was used to H2 production simultaneous photodegradation with individual or both kinds of dyes (namely, methyl orange (MO), eosine Y (EY), methyl blue (MB) and rhedamine B (RhB)), respectively. As the figures indicated, although the rate of hydrogen production saw a steady increase in the single dye in the solution, it was outmatched by any two kinds of dyes group, which played significant positive synergism effects. In particular, when MB/EY group was added intoTEOA solution, the QE reached a peaking of 25.42% dramatically. In addition, real textile industrial wastewater was applied in this system, and the QE was 20.45%, which was 1.32 fold that of clean water. The crucial factor in improving the photocatalytic activity was that appropriate amount of functional 0D-2D Schottky barrier heterostructures were constructed. Such a novel architecture provided a large and intimate contact interface for fast interfacial photo-charges separation. The effective charge transfer from TNS to Pt was demonstrated by the significant enhancement of photocurrent responses in 0D-2D Pt-TNS composite. This work created new opportunities for designing and constructing highly efficient photocatalysts by interfacial engineering.

Synergistic effect of Fe2O3/Ho2O3 Co-modified 2D-titanate heterojunctions on enhanced photocatalytic degradation

TiO2-based nanosheets (TNSs) co-modified by Fe2O3 and Ho2O3 were synthesized by one-pot hydrothermal method using Fe(NO3)3 and Ho(NO3)3 as precursors compositing with TiO2. The Fe2O3/Ho2O3-TNSs heterojunctions possessed a thickness of approximately 3–4 nm, large specific surface area of 210–310 cm2/g, with Fe2O3 and Ho2O3 nanoparticles highly dispersed over the surface of the nanosheets. The crystallization of the samples gradually increased with the amount of Fe2O3 nanoparticles, which was confirmed by the XRD, BET and Raman spectra, indicating that Ho2O3 and Fe2O3 influenced the crystallinity and structure evolution of the TNSs, besides, led to an improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be efficiently improved by an appropriate amount of modification. The Fe2O3/Ho2O3-TNSs exhibited synergistic effect on photocatalytic degradation of RhB as well as MO under visible light. The highest efficiency was obtained by 0.05%-Fe2O3/Ho2O3-TNSs (Fe:Ho:Ti = 0.05:1:100), which was 8.86 and 6.72 times than that of individual 1.0%-Ho2O3-TNSs (Ho:Ti = 1:100) and 0.05%-Fe2O3-TNSs (Fe:Ti = 0.05:100), respectively. The possible mechanism for enhanced visible-light-induced photocatalytic activity was proposed. Ho2O3 introduced in the photocatalysts may act as the hole capture while Fe2O3 may share the same Fermi levels with TNSs and serve as the electron capture center in the n-n-p system, which reduced the recombination rate of photo-induced electron-hole pairs.

Two-dimensional TiO2-based nanosheets co-modified by surface-enriched carbon dots and Gd2O3 nanoparticles for efficient visible-light-driven photocatalysis

Two-dimensional TiO2-based nanosheets (TNSs) co-modified by surface-enriched carbon dots (CDs) and Gd2O3 nanoparticles: (Gd-C-TNSs), capable of exhibiting visible-light-driven photo catalysis were synthesized using a two-pot hydrothermal route. The samples had a sheet-like structure, thickness of approximately 3.6nm, large specific surface area of 240–350cm2/g. The CDs (2–3nm) and Gd2O3 nanoparticles (1–2nm) were highly dispersed over the surface of the nanosheets. The co-modification by Gd2O3 nanoparticles and CDs influenced the crystallinity, crystal structure, and surface area of the TNSs, and improved the visible-light absorption. Surface photocurrent and fluorescence spectral studies revealed that the photo-generated charge carrier separation efficiency could be improved by an appropriate amount of modification. A very high efficiency was obtained using 0.5 at% Gd/Ti and 3.0g/L of CDs. The visible-light-induced photocatalytic activity is enhanced under the isolated Cr(VI) system, isolated Rhodamin B (RhB) system, and the synergism between RhB degradation and Cr(VI) reduction for the Gd-C-TNSs photocatalysts. Initially, the photocatalytic activity gradually increased with an increase in the amount of CDs, and then decreased after attaining a maximum, in the case where 0.5 at% Gd/Ti and 3.0g/L of CDs were used. The enhancement in the photocatalytic activity was attributed to the synergetic effect of the Gd2O3 nanoparticles, TNSs, and CDs in the Gd-C-TNSs composites. The effect led to a fast separation and slow recombination of photo-induced electron–hole pairs. An alternate mechanism for enhanced visible-light photocatalytic activity was also considered.

Visible light induced photocatalytic removal of Cr(VI) over TiO2-based nanosheets loaded with surface-enriched CoOx nanoparticles and its synergism with phenol oxidation

Visible-light-driven (VLD) CoOx loaded TiO2-based nanosheets (Co-TNSs) with surface-enrich CoOx nanoparticles were successfully synthesized by using a facile one-pot hydrothermal method. The photocatalysts were characterized by SEM, AFM, HRTEM, XRD, Raman, XPS, FL and the surface photocurrent (SPC) technique, etc. The as-synthesized samples exhibit sheet-like structure with large specific surface area (260–350cm2/g) and small thickness (3–4nm). The CoOx nanoparticles (1–2nm) are highly dispersed on the surface of TNSs. Loaded CoOx nanoparticles not only have influenced the crystal structure, crystallinity and surface area of the TNSs, but also resulted in considerable enhancement of visible-light (VL) absorption and a red-shift of the band gap of the TNSs. XPS results reveal that cobalt mainly exists in the form of Co2+ and Co3+, and the binding energies of TiO bonds are changing with the loaded amount of CoOx nanoparticles. FL and SPC results indicate appropriate amount of CoOx (2.5at.%) loading can effectively inhibit the recombination of photo-generated electron-hole pairs, thus improve the separation efficiency of charge carriers.The photocatalytic activity of the samples was evaluated by the dichromate (Cr(VI)) solution under VL irradiation. It can be found that the Co-TNSs photocatalysts showed excellent VL photocatalytic activity for the removal of Cr(VI). Initially the photocatalytic activity increased with the content of CoOx, and then decreased after attaining a maximum value at an optimal content (2.5at.%) for degradation of aqueous Cr(VI) solution. The addition of Ca2+ promotes photocatalysis owing to its ionic bridging function in the form of TiOH+Cr(VI)–Ca2+Cr(VI) linkages, while SO42− slightly inhibits the photo-reduction of Cr(VI), indicating good synergy of photocatalysis and adsorption even at higher ionic strength of electrolyte. The photocatalytic reduction of Cr(VI) is also significantly promoted by phenol and synergism between Cr(VI) reduction and degradation of phenol which is demonstrated by measuring the effect of multiple usage of Co-TNSs on its photocatalytic efficiency. Desorbed Co-TNSs (Co-TNSs-Des) are easily regenerated and reused for Cr(VI) removal with excellent performance. A possible alternate mechanism for the enhancement of photocatalytic activity under visible light irradiation is also proposed.

A novel synthesis of ultrathin TiO2-based nanosheets with excellent photocatalytic performance

Ultrathin TiO2-based nanosheets (TNSs) are prepared by a novel and facile hydrothermal route. It is found that TiO2 nanoparticles can be completely converted into layered titanate structure when they are first treated with high concentrated NaOH solution, which is crucial to hinder the formation of tube-like structure and facilitate the final synthesis of pure sheet-like structure. Besides, ultrathin TNSs composed of 1–3 monolayers with an interlayer spacing of ca. 1.02nm can be obtained by a further treatment of exfoliation. The prepared TNSs exhibit much higher photocatalytic activity than commercial P25 TiO2. Owing to the advantages of uniform morphology, ultrathin thickness, and high charge-separation efficiency, the obtained TNSs may have a wide application prospect in photocatalysis and some related fields.

Facile one-pot fabrication and high photocatalytic performance of vanadium doped TiO2-based nanosheets for visible-light-driven degradation of RhB or Cr(VI)

Vanadium doped TiO2-based nanosheets (V-TNSs) with different V/Ti ratios were prepared by a facile one-pot hydrothermal method using vanadium nitrate and P25 as the vanadium precursor and titanium precursor, respectively. The results indicated that as-synthesized photocatalysts exhibited sheet-like structure with large specific surface area (270–340cm2/g) and small thickness (4–5nm). XPS results revealed that vanadium exists in the form of V4+ and V5+, and the binding energies of TiO bonds have been changed with the concentration of vanadium. Vanadium doping resulted in considerable enhancement of visible light absorption, red-shift, and the band-gap of photocatalysts reduced from 3.18eV to 2.91eV. The density functional theory (DFT) calculations for band structure and total energy also provided a good explanation and further confirmation for the experimental results. It has been found that the photo-activity increased gradually with the concentration of vanadium, and then decreased after attaining a maximum with an optimal content of vanadium at 1.0at.% for RhB or Cr(VI). The reaction rate Kapp of 1.0%-V-TNSs are 9.27-fold and 3.26-fold as compared to undoped TNSs under UV–vis and visible light irradiation, respectively. The cyclic tests that performed six times demonstrated high stability and reusability of the photocatalysts. A possible alternate mechanism for the enhancement of the photocatalytic activity under visible-light irradiation was also proposed.

Preparation and characterization of TiO2-based nanosheets for photocatalytic degradation of acetylsalicylic acid: Influence of calcination temperature

TiO2-based nanosheets (BNSs) were synthesized via hydrothermal method and acid-washing procedure, followed by calcinating at different temperatures in air. The resulting TiO2-BNSs were characterized by XRD, SEM, DRS and PL. The photoelectrochemical properties of TiO2-BNSs were measured through transient photocurrent response (TPR), open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The prepared TiO2-BNSs were used to the photocatalytic degradation of acetylsalicylic acid. The results indicated that the samples calcinated at different temperatures exhibited the nanosheets architectures with the lengths in the range of 500–1500nm and thickness of approximately 30nm. The crystallinity of the samples enhanced as increasing the calcination temperature from 400°C to 600°C. Among the TiO2-BNSs samples, the 500°C-calcinated nanosheets (TiO2-BNSs-500) exhibited the relatively uniform and regular nanosheet structure. The phase transformation from anatase to rutile phase happened at 500°C. TiO2-BNSs-500, TiO2-BNSs-550 and TiO2-BNSs-600 possessed the biphase structure of anatase–rutile. And, the visible light absorption, electron–hole pairs separation and transfer efficiency, photocatalytic activities for the degradation of acetylsalicylic acid and OH yield of the samples presented the similar variation tendency which improved as increasing the calcinated temperatures from 400 to 500°C and then declined at 550 and 600°C. Accordingly, the degradation rate of acetylsalicylic acid for 120min reaction was 87.8% when TiO2-BNSs-500 was employed as the photocatalyst. The photocatalytic degradation reaction fitted the pseudo-first-order kinetics and OH was the crucial oxidative species.

A facile one-pot synthesis of TiO2-based nanosheets loaded with MnxOy nanoparticles with enhanced visible light–driven photocatalytic performance for removal of Cr(VI) or RhB

This paper reports a facile one-pot approach for MnxOy (Mn=Mn2+, Mn3+) loaded TiO2-based nanosheets (Mn–TNSs) with surface enrichment of MnxOy nanoparticles via a simple hydrothermal route. The as-synthesized samples showed clearly sheet-like structure, with high specific surface area (200–300m2/g) and small thickness (ca. 4nm). The small MnxOy nanoparticles with uniform size (1–2nm) were highly dispersed on the surface of the TNSs. Loaded MnxOy not only have influenced the crystal structure and surface area of the TNSs, but also resulted in considerable enhancement of visible-light absorption and red-shift for TNSs. The results of X-ray photoelectron spectroscopy showed that Mn2+ and Mn3+ co-exist in Mn–TNSs. The loading of MnxOy on TNSs resulted in changes in binding energies of Ti and O. The concentration of Ti3+ increased gradually with the amount of loaded MnxOy increasing. The photo-reactivity of the samples were evaluated by measuring the formation of photo-induced hydroxyl radical (OH) using coumarin (COU) as a probe molecule and photocatalytic degradation of Rhodamin B (RhB) and dichromate (Cr(VI)) under visible-light irradiation. It has been found that the Mn–TNSs photocatalysts showed better visible-light photocatalytic activity for aqueous RhB or Cr(VI) solution. The photocatalytic activity gradually increased with the content of MnxOy increasing initially, and then decreased after attaining a maximum value at an optimal content (2.5 at.%) of MnxOy in TNSs for degradation of aqueous RhB or Cr(VI) solution, respectively. The cyclic tests that performed five times demonstrated high stability and recyclable usability of the photocatalysts. A possible alternate mechanism for the enhancement of the photocatalytic activity under visible-light irradiation was also proposed.

One-step hydrothermal synthesis of C-N-S-tridoped TiO2-based nanosheets photoelectrode for enhanced photoelectrocatalytic performance and mechanism

C-N-S-tridoped TiO2-based nanosheets(BNSs) photoelectrode was prepared via a one-step hydrothermal strategy of the Ti plate in mixed solution of NaOH and cystine, followed by acid-washing and calcination. The resulting samples were characterized by X-ray photoelectron spectroscopy (XPS), scanning electrons microscopy (SEM), X-ray diffraction (XRD) and UV-vis diffuse reflectance spectra (DRS). XPS analysis indicated that C, N and S were transferred into the lattice of TiO2. Highly ordered TiO2-BNSs with the sheet lengths of 500–1500nm and thickness of about 30nm were observed. XRD patterns showed that TiO2-BNSs before and after C, N and S tridoping were biphase of anatase-rutile. And tridoping with C, N and S could promote the phase transition from anatase to rutile and restrain growth of rutile crystallites. In addition, a shift of the absorption edge towards low energy and the intense visible light absorption were achieved. Photoelectrochemical (PECH) properties of the C-N-S-tridoped TiO2-BNSs photoanode were investigated through transient photocurrent response (TPR), open-circuit potential (OCP) and electrochemical impedance spectroscopy (EIS). The photoelectrocatalytic(PEC) performances were evaluated by the yield of •OH radicals and degradation of methyl orange(MO) under Xenon lamp irradiation. The results showed that C-N-S-tridoped TiO2-BNSs photoelectrode revealed high photogenerated current of 0.69mAcm−2, open-circuit photovoltage of -0.66mVcm−2, generation of •OH radicals and PEC efficiency of 96.8% for the degrading MO. Moreover, the enhanced PEC mechanism was proposed. The high PEC performance could be ascribed to the tridoping with C, N and S, which could not only improve the light harvesting in visible region but also enhance the mobility and separation efficiency of photogenerated charge carriers.

A facile one-pot synthesis of gadolinium doped TiO2-based nanosheets with efficient visible light-driven photocatalytic performance

Gadolinium doped TiO2-based nanosheets (Gd-TNSs) with different Gd/Ti ratios are prepared by a facile one-pot hydrothermal method using gadolinium nitrate as the gadolinium precursor. The photocatalysts are characterized by high-resolution transmission electron microscopy (HRTEM), Raman spectra, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet–visible light diffuse reflectance spectra (DRS), fluorescence spectra (FL), and N2 adsorption–desorption measurement. The as-synthesized samples show clearly sheet-like structure, with the width of about 30–100 nm, length greater than 100 nm, and high specific surface area (200–300 m2/g). The patterns of XRD and Raman analyses indicate that doped gadolinium has obvious influence on the structure of samples. The band-gap energy (E g) of photocatalysts reduce from 3.17 to 3.02 eV with the content of gadolinium increasing from 0.1 to 1.5 at. %. The FL emission intensity initially decreases with the content of Gd increasing and then increases after minimizing at 0.5 %-Gd-TNSs, which reveals that appropriate amount of gadolinium doping can effectively inhibit the recombination of photo-generated electrons and holes. The adsorption capacity and photocatalytic activity are evaluated by Rhodamine B (RhB). The best photocatalytic performance is obtained when the doping ratio of gadolinium is 0.5 at. %. The visible reaction rate (K app) of 0.5 %-Gd-TNSs was 2.0-fold as compared to TNSs, and 4.7-fold as compared to P25. The possible mechanisms for enhanced visible-light photocatalytic activities are discussed in detail.

Effect of holmium doping on the structure and photocatalytic behavior of TiO2-based nanosheets

A series of holmium-doped TiO2-based nanosheet (Ho-TNS) photocatalysts with different Ho/Ti molar ratios were prepared via a simple hydrothermal method. The photocatalysts were characterized by field-emission scanning electron microscope, high-resolution transmission electron microscope, X-ray diffraction (XRD), Raman Spectroscopy, X-ray photoemission spectroscopy, nitrogen adsorption–desorption isotherm measurement, ultraviolet–visible light diffuse reflectance spectra (DRS), and fluorescence spectra (FL). The TEM images of Ho-TNS exhibit clearly sheet-like structures and existence of the (201) plane of H2Ti3O7. The increased (101) peak intensity in XRD spectrum and the enhanced Eg mode (141 cm−1) in Raman spectrum indicate that Ho doping has obvious influence on the formation and structure of Ho-TNS, which can be explained by the formation of Ho–O–Ti bonds. With the doping ratio (Ho/Ti molar ratio) increasing from 0 to 2.0 %, the absorption edge shifts to a longer wavelength, and the band-gap of photocatalysts reduces from 3.18 to 3.07 eV. The decline of FL intensity implies that the photocatalysts with higher Ho content have higher electron–hole separation efficiency. However, after Ho doping, the surface structure of specimens is significantly altered, which will lead to the specific surface areas and adsorption capacity decrease. Under the combined effect of the variables, the photocatalyst with a doping ratio of 1.0 % reaches the best photoactivity, which is 1.90-fold and 12.38-fold higher compared with undoped TNS and P25 under visible light, respectively. The high photoactivity of the prepared Ho-TNS indicates that it may be useful for dealing with wastewater.

Carbon deposited TiO2-based nanosheets with enhanced adsorption ability and visible light photocatalytic activity

Carbon deposited TiO2-based nanosheets (C-TNS) photocatalysts were prepared by a two-step hydrothermal treatment of Degussa P25 titania using glucose as the carbon precursor. The microstructures, adsorption abilities, and visible light photocatalytic properties of the samples were investigated. Carbon deposition has significantly enhanced the visible light absorbing ability and dye molecules adsorption ability of TiO2-based nanosheets (TNS). The XPS result suggests that the deposited carbon mainly exists in the form of carbonaceous species, and carbon deposition results in the decrease of hydroxyl oxygen. When the glucose solution concentration is 2g/L, the obtained C-TNS possess the highest visible light photoactivity in degrading Rhodamine B (RhB), which is 12 times and 3 times of that of P25 and the pure TNS, respectively. The good reusability of C-TNS in the cyclic degradation experiments implies a potential application for dealing with organic pollutants. It is suggested that carbon deposition is a promising way to enhance the visible light photoactivity of TiO2-based nanosheets.

Dimensionality-dependent photocatalytic activity of TiO2-based nanostructures: nanosheets with a superior catalytic property

TiO2-based nanostructures usually possess excellent photochemical properties. However, the relationship between their dimensionality and photocatalytic activity was rarely investigated. In this study, a series of TiO2-based nanostructures in various dimensionalities (such as nanosheets, nanotubes) were obtained by hydrothermal treatment of P25, and the process of structural evolution was also systematically investigated by TEM, BET, Raman, and XRD analysis. Much higher rate constant (3.7 × 10−2 min−1) for the degradation of rhodamine B was found for nanosheets, comparing with those of three-dimensional P25 nanoparticles (0.59 × 10−2 min−1) and one-dimensional nanotubes (0.85 × 10−2 min−1). It is found that the hydrothermally prepared TiO2-based nanosheets possess small thickness (ca. 5 nm) and plentiful surface hydroxyl groups, and the reason why TiO2-based nanosheets possess superior photocatalytic activity is also discussed in detail from the microstructure and surface chemical states. In addition, TiO2-based nanosheets exhibit good reusability in the cyclic experiments, implying a potential application for photocatalytic degradation of organic pollutants.

Study on enhanced photocatalytic performance of cerium doped TiO2-based nanosheets

Cerium doped TiO2-based nanosheets (Ce-TNSs) photocatalysts were prepared by a one-pot hydrothermal method using cerium nitrate as the cerium precursor. The photocatalysts were characterized by high-resolution transmission electron microscope (HRTEM), X-ray diffraction (XRD), Raman spectra, ultraviolet–visible light diffuse reflectance spectra (DRS), X-ray photoemission spectroscopy (XPS) and fluorescence spectra (FL). The results show that Ce3+ and Ce4+ co-exist in Ce-TNS. The doping leads to changes in binding energies of Ti and O. The concentration of Ti3+ increases gradually when the cerium doping amount keep increasing. Appropriate amount of cerium doping can significantly inhibit the recombination of electron–hole pairs, which is proved by the decline in the intensity of the fluorescence spectra. Ce-TNS with doping ratio of 0.5% (molar ratio) possesses the highest photocatalytic activity when degrading Rhodamine B (RhB), which is 5 times and 1.6 times of that of P25 and the undoped TNS, respectively. It is suggested that cerium ions are efficient electron trappers to improve the separation efficiency of electrons and holes.

Preparation, structure, and properties of polyurethane foams modified by nanoscale titanium dioxide with three different dimensions

TiO2-based nanosheets (TiNSs), TiO2-based nanotubes (TiNTs) were prepared by hydrothermal processing, and polyurethane foams with TiO2 nanopowders (P25), TiNSs and TiNTs were synthesized by free-rising foaming method. The Fourier-transform infrared (FT-IR) spectra show that the addition of titanium dioxide does not affect the chemical structure of polyurethane foam. However, microscope observations show that PU/TiNSs composite foams have more uniform cells and the average aperture smaller than that of pure polyurethane foams. According to the results of thermal analysis, the PU/TiNSs composite foams have better thermal stability, the temperature of decompostion occurring with a maximum weight loss rate is about 30 °C higher than that of pure PU foams. The decompostion temperatures are 167 °C and 148 °C for the PU/P25 composite foams and the PU/TiNTs composite foams respectively, which are lower than that of pure PU foams. Moreover, with the addition of the fillers, the sound absorption property also has changed; the addition of TiNSs improved the sound absorbing property efficiently. The better thermal stability and sound absorption of PU/TiNSs composite foams are mainly due to the uniform cells diffuse and smaller aperture.