Combined Sol-gel Method Research Articles

Synthesis of TiO2/rGO Nanocomposites with Enhanced Photoelectrochemical Performance and Photocatalytic Activity

In this paper, a facile and efficient method combined sol–gel method with hydrothermal process was employed for preparing titanium dioxide (TiO[Formula: see text]/reduced graphene oxide (rGO) nanocomposites without using any reductants or surfactants. This approach leads to the reduction of graphene oxide (GO) and the growth of TiO2 nanorods simultaneously. The results reveal that the TiO2 short nanorods with average size of 15[Formula: see text]nm in length and 10[Formula: see text]nm in diameter were uniformly grown on the rGO sheets with high dispersion. Compared with the pure TiO2 nanoparticles, the TiO2/rGO composites exhibit strong absorption in the visible light range. The photocurrent density of nanocomposites reached 0.826[Formula: see text]mA/cm2 under the simulated sunlight illumination, which is 3.5 times than that of pure TiO2. An enhancement of photocatalytic hydrogen formation rate for the water splitting was observed over the TiO2/rGO composite photocatalysts, the fastest formation rate can reach 889.28[Formula: see text][Formula: see text]mol[Formula: see text]g[Formula: see text]h[Formula: see text] when TiO2 coupling with 1wt.% rGO. Also the hydrogen production rate is about 3.27 times larger than pure TiO2 and 2.23 times than P25 due to the excellent electron trapping and transportation properties of rGO and the synergistic effect between TiO2 and rGO.

Mesoporous TiO₂ spheres interconnected by multiwalled carbon nanotubes as an anode for high-performance lithium ion batteries.

We report on the excellent electrochemical response of lithium ion batteries that use a composite material comprised of mesoporous titanium dioxide (MTO) spheres and multiwalled carbon nanotubes (MWCNTs) for the anode. The composite structure was synthesized via a combined sol-gel and solvothermal method, and the batteries exhibited unprecedented discharge capacity, cycling stability, and reversibility when compared to those based on commercially available TiO2 nanopowders and mesoporous TiO2 spheres. The inclusion of the composite structure resulted in an improvement in electronic and ionic conductivity, a larger surface area, and a colossal number of open channels in the synthesized structure that allowed for lithium ion intercalation. We achieved a Coulombic efficiency of nearly 100% and a discharge capacity as high as 316 mA h g(-1) at a rate of C/5, which is 1.9 times higher than that which is practically attainable with TiO2. Moreover, we observed a capacity loss of only 3.1% after 100 cycles, which indicates that the synthesized structure has a highly stable nature.

Controlled synthesis of TiO2using a combined sol gel and dielectrophoresis method

A controlled synthesis of titanium dioxide nanoparticles (TiO2-NPs) with uniform size and a specific crystal structure could be achieved by a combined sol gel/dielectrophoresis (DEP) approach. The applied voltage could influence the crystal structure and particle size.

Flexible Pd/CeO2–TiO2 nanofibrous membrane with high efficiency ultrafine particulate filtration and improved CO catalytic oxidation performance

Flexible CeO2–TiO2 fibrous membrane was prepared by an electrospinning combined sol–gel method.

Modification of Ultra-Low Density Fiberboards by an Inorganic Film Formed by Si-Al Deposition and their Mechanical Properties

To improve mechanical properties of ultra-low density fiberboards (ULDFs), Si-Al compounds were mixed together with fibers during preparation of ULDFs, forming a thin film on the surface of the fibers via hydrogen bonding. This work mainly optimized two proposed methods in which the inorganic thin film was assembled on the surface of fibers, in terms of its effect on the mechanical properties of fibers. Microstructural characterization (such as micromorphology and elemental distribution, chemical bonding, and crystalline phase) of Si-Al compounds and ULDFs was done to evaluate the effects. The results revealed that an inorganic thin film (probably Al2O3-SiO2) covered the surface of the fibers. Compared with the control specimen, the modulus of elasticity, modulus of rupture, and internal bond strength of the specimen treated by the sol-gel process increased from 3.87 MPa to 13.19 MPa, 0.05 MPa to 0.16 MPa, and 0.010 MPa to 0.025 MPa, respectively. Based on its higher mechanical properties, a combined sol-gel method was judged to be better for enhancement of fibers than a separate deposition method.

Pr, N, and P tri-doped anatase TiO2 nanosheets with enhanced photocatalytic activity under sunlight

Pr, N, and P tri-doped anatase TiO2 nanosheets (PrNPTO) were synthesized by a combined sol-gel solvothermal method and characterized by X-ray diffraction, transmission electron microscopy, N2 adsorption-desorption, X-ray photoelectron spectroscopy, UV-vis absorbance spectroscopy, and photoluminescence spectroscopy. When the Pr-doping concentration was 1.75 wt% and calcination temperature employed was 550 °C, the resulting PrNPTO showed the highest photoactivity towards the degradation of methylene blue under visible and UV light irradiation. PrNPTO also displayed superior photoactivity towards the degradation of 4-chlorophenol under sunlight (kapp = 3.90 × 10−2 min−1) over the non-doped, single-doped, and co-doped samples, and P25 TiO2 (kapp = 1.17 × 10−2 min−1). The high photoactivity of PrNPTO was attributed to the increased UV and visible light absorption properties, reduced recombination of photogenerated carriers, increased surface hydroxyl content, and improved surface textural properties. PrNPTO was highly efficient and stable under simulated sunlight irradiation, which are essential attributes for practical application in environment-related remediation schemes.

Mesoporous TiO2 nano-spheres: Electrospray combined sol-gel fabrication and application to organic phosphorus degradation

In this work, electrospray technique combined sol-gel method was used to prepare porous TiO2 film. X-ray Photoelectron Spectroscopy (XPS), X-Ray Diffraction (XRD), and Scanning Electron Microscope (SEM) analyses were conducted to examine the chemical composition, phase structure, and surface morphology of the sprayed TiO2 film. After calcined at 450 °C in air atmosphere for 2 h, mesoporous TiO2 nano-spheres clusters were formed on the surface of silicon wafer and the average size of nano-spheres was 250 nm. Ti presented as Ti4+ oxidation state in TiO2 film, and the TiO2 film exhibited the anatase phase. The sprayed porous TiO2 films were employed as photocatalyst to degrade organic phosphorus in water samples. Compared with the TiO2 film prepared by Sol-Gel spin-coating method, the porous TiO2 film deposited by electrospray combined sol-gel method showed higher photocatalytic activity.

Nanocrystalline Mixed Oxides Containing Magnesium Prepared by a Combined Sol-Gel and Self-Combustion Method for Catalyst Applications

MgFe2O4 spinel ferrite and La0.6Pb0.2Mg0.2MnO3 perovskite nanopowders were synthesized by a combined sol-gel and self-combustion method and heat treatment. The morphological and structural characterization of the obtained powders has been performed with various techniques: X-ray diffraction (XRD), SEM observations, EDAX spectroscopy and BET analysis. The samples have been catalytically tested in flameless combustion reaction of acetone, benzene, propane and Pb free gasoline at atmospheric pressure. The results revealed a higher catalytic activity of La0.6Pb0.2Mg0.2 MnO3 perovskite than that of MgFe2O4 ferrite. This higher catalytic activity can be ascribed to smaller crystallite size (27 nm), larger surface area (8.5 m2/g) and the presence of manganese cations with variable valence (Mn3+ - Mn4+). The current results suggest that La0.6Pb0.2Mg0.2MnO3 perovskite is preferable to the Mg ferrite and that it can be a promising catalyst for acetone and propane combustion at low temperatures.

Robotic deposition and in vitro characterization of 3D gelatin−bioactive glass hybrid scaffolds for biomedical applications

The development of inorganic-organic hybrid scaffolds with controllable degradation and bioactive properties is receiving considerable interest for bone and tissue regeneration. The objective of this study was to create hybrid scaffolds of gelatin and bioactive glass (BG) with a controlled, three-dimensional (3D) architecture by a combined sol-gel and robotic deposition (robocasting) method and evaluate their mechanical response, bioactivity, and response to cells in vitro. Inks for robotic deposition of the scaffolds were prepared by dissolving gelatin in a sol-gel precursor solution of the bioactive glass (70SiO2 -25CaO-5P2 O5 ; mol%) and aging the solution to form a gel with the requisite viscosity. After drying and crosslinking, the gelatin-BG scaffolds, with a grid-like architecture (filament diameter ∼350 µm; pore width ∼550 µm), showed an elasto-plastic response, with a compressive strength of 5.1 ± 0.6 MPa, in the range of values for human trabecular bone (2-12 MPa). When immersed in phosphate-buffered saline, the crosslinked scaffolds rapidly absorbed water (∼440% of its dry weight after 2 h) and showed an elastic response at deformations up to ∼60%. Immersion of the scaffolds in a simulated body fluid resulted in the formation of a hydroxyapatite-like surface layer within 5 days, indicating their bioactivity in vitro. The scaffolds supported the proliferation, alkaline phosphatase activity, and mineralization of osteogenic MC3T3-E1 cells in vitro, showing their biocompatibility. Altogether, the results indicate that these gelatin-BG hybrid scaffolds with a controlled, 3D architecture of inter-connected pores have potential for use as implants for bone regeneration.

Synthesis of LiV<sub>3</sub>O<sub>8</sub> Crystallites via an Improved Citric Acid Assisted Sol-Gel Method

Lithium trivanadate (LiV3O8) powders have many attractive characteristics such as high specific energy density, good rate capacity and long cycle life due to their unique crystal structure and outstanding structure stability as cathode material for rechargeable lithium batteries. LiV3O8 crystallites were synthesized under different conditions via a combined ultrasonic irradiation and sol-gel method. The as-prepared LiV3O8 powders were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), Fourier transform infrared (FT-IR) absorption spectra. The thermal decomposition process was investigated using thermogravimetric (TG) and differential scanning calorimetry (DSC). The effects of molar ratios of metal ion/citric acid and calcinations temperature on phases and microstructure of the powders were investigated. Results indicate that calcinations temperatures have significant influence on the particle morphology, particle size and particle size distribution of the powders. The pure and rod-like LiV3O8 powders with an average size of 0.2-1 μm are obtained at 350 and 400 °C. With the increase of calcinations temperature, the powders exhibit preferred growth orientation along (100) planes. The crystallites obtained at 550 and 600 °C are composed by LiV3O8 with a small amount of Li0.3V2O5 phase, both of which exhibit tabular morphologies with an average size of 2-10 μm.

Study on a Titanate Film and its Photocathodic Protection Effect for 403 Stainless Steel

TiO2 and titanate semiconductor nanomaterials have attracted tremendous interest due to their exceptional electronic and mechanical properties. In the present work, a titanate nanowire network film was prepared by a combined sol-gel and hydrothermal method. The morphology, chemical composition and photoelectrochemical behavior of the film were characterized by scanning electron microscopy, X-ray diffraction, and electrochemical techniques, respectively. The results showed that the titanate film exhibited a special three-dimensional porous structure composed of titanate nanowires. When the 403 stainless steel in a 0.5 M NaCl solution was coupled to the titanate film as a photoanode in a 1.0 M NaOH solution under illumination, its potential decreased by about 570 mV, indicating the film produced a good photocathodic protection effect for the steel. EIS measurements revealed that the charge transfer resistance of the electrochemical reaction process for the steel coupled to the titanate film decreased considerably.

Preparation and Photocathodic Protection Properties of NiP/TiO<sub>2</sub> Bilayer Coating on Low Carbon Steel

The NiP/TiO2 bilayer coatings were prepared on low carbon steel substates using a combined electroless plating and sol-gel method. The performance of photocathodic protection of the bilayer coatings was investigated by the electrochemical method. The results show that the coating with four TiO2 layers and calcined at 400°C exhibits the highest photoelectrochemical efficiency and the best corrosion resistance property.

Simultaneous removal of ethanol, acetaldehyde and nitrogen oxides over V-Pd/γ-Al 2O 3-TiO 2 catalyst

Abstract V-Pd/γ-Al 2O 3-TiO 2 catalysts with different vanadium contents were prepared by a combined sol-gel and impregnation method. X-ray diffraction (XRD), N 2 adsorption-desorption (BET), X-ray photoelectron spectroscopy (XPS) and catalytic removal of ethanol, acetaldehyde and nitrogen oxides at low temperature (<300°C) were used to assess the properties of the catalysts. The results showed that the sample with 1wt% vanadium exhibited an excellent catalytic performance for simultaneous removal of ethanol, acetaldehyde and nitrogen oxides. The conversions of ethanol, acetaldehyde and nitrogen oxides at 250°C were 100%, 74.4% and 98.7%, respectively. V-Pd/γ-Al 2O 3-TiO 2 catalyst with 1 wt% vanadium showed the largest surface area and higher dispersion of vanadium oxide on the catalyst surface, and possessed a larger mole fraction of V 4+ species and unique PdO species on the surface, which can be attributed to the strong synergistic effect among palladium, vanadium and the carriers. The higher activity of V-Pd/γ-Al 2O 3-TiO 2 catalyst is related to the V 4+ and Pd 2+ species on the surface, which might be favorable for the formation of active sites.