TiO2-SiO2 Composites Research Articles

X-ray characterization, structural analysis, antibacterial activity, and self-cleaning property of Cu-doped TiO2-SiO2 nanocomposite prepared by sonochemical process

TiO2-SiO2 nanocomposites with different copper (Cu) precursor loadings were prepared by a one-step sonochemical process. The mole ratio of Cu precursor in TiO2-SiO2 composite was varied at 0.004, 0.008, 0.020, and 0.040, respectively. The specific X-ray characterization techniques on crystalline structure, chemical composition, and chemical states of Cu-doped TiO2-SiO2 composite were carried out by X-ray diffraction technique (XRD), X-ray fluorescence (XRF), and X-ray photoelectron spectroscopy (XPS), respectively. Surface morphology and chemical bonding of Cu-doped TiO2-SiO2 composite were monitored by field emission scanning electron microscope (FE-SEM) and Fourier transform infrared spectrophotometer (FTIR). For antibacterial properties, the inhibition zone of antimicrobial activity was investigated by varying amounts of Cu precursors in the TiO2-SiO2 composite. After that, Cu-doped TiO2-SiO2 composite powder with different Cu precursor ratios was mixed in PMMA solution and deposited on glass slides to study the optical property and hydrophilicity by UV-VIS-NIR spectrophotometer and contact angle method. XRD patterns of Cu-doped TiO2-SiO2 nanocomposites show the formation of the main TiO2 anatase phase with the ultrafine particles observed by FE-SEM images. FT-IR spectra of the composites are assigned to the prominent peaks of the Ti-O-Ti and Ti-O-Si bond relating to the TiO2-SiO2 host matrix. Meanwhile, TiO2-SiO2 composites with Cu precursor at 0.004 mol ratio can significantly enhance the antibacterial activity with a large inhibition zone. The contact angle value of Cu-doped TiO2-SiO2 nanocomposite film at 0.040 Cu precursor mole ratio in the TiO2-SiO2 matrix resulted in the optimized composite ratio for achieving a hydrophilic surface on the substrate.

The Properties and Activity of TiO2-based Nanorods as an Anti-Fouling Agent and a Photocatalyst

The properties and activity of TiO2-based nanorods as an antifouling agent and a photocatalyst for the catalytic degradation of methylene blue (MB) have been investigated. A modification of TiO2 with SiO2 was first carried out to enlarge the surface area. In order to enhance the TiO­2 photo response to the visible light region, a further modification of TiO2-SiO2 (TS) composites with polyaniline (PANI) was also conducted. The nanorod TiO2 exhibited an anatase structure based on the diffraction patterns. The TEM images showed that some TiO2 molecules were attached around SiO2 with a random orientation. The TiO2-SiO2-PANI (TS-PANI) exhibited the largest specific surface area (SBET) of about 256.85 m2/g. The profile on the AFM images of the composites showed that the nano-roughness of the coatings was confirmed. The photocatalytic activity was evaluated through the decomposition of MB both on the powder and the coated composites. The photocatalytic activity on the coatings was verified due to further application as anti-fouling coatings involving photocatalytic mechanism. The decomposition of MB using TS-PANI powder and TS-PANI coating composites was 89.5% and 90.2 %, respectively, with the irradiation time on the coatings was 20 min longer. The anti-fouling activity through the photocatalytic mechanism and nano-roughness surface was confirmed by the inhibition of barnacle growth on the teakwood surface immersed for two months in the sea.

Propylamine Silica-Titania Hybrid Material Modified with Ni(II) as the Catalyst for Benzyl Alcohol to Benzaldehyde Conversion

SiO2-TiO2@propylamine-Ni(II) as the catalyst for the benzyl alcohol oxidation has been synthesized by utilizing rice husk ash as the SiO2 source. This research was started by extracting SiO2 from rice husk ash and continued by synthesizing the SiO2-TiO2 composite using titanium(IV) tetraisopropoxide (TTIP) as TiO2 precursor and PEG-40 as template. The composite functionalization and metal modification were carried out by adding (3-aminopropyl)triethoxysilane (APTES) as the source of propylamine linker and impregnating NiCl2·6H2O as the nickel precursor, respectively. The catalysts were synthesized by varying the ratios between each component within the material. The prepared materials were then characterized using ATR-IR, XRD, XRF, PSA, SAA, AAS, SEM-EDX, HR-TEM, and TGA. The catalyst activity was investigated by applying it to the oxidation reaction of benzyl alcohol to benzaldehyde with H2O2 as the oxidizing agent under sonication system. The obtained products were then analyzed by using GC-MS to quantify the success of the reaction. All characterizations performed in this research generally indicate the success in the synthesis of SiO2-TiO2@propylamine-Ni(II) materials. Under the same condition including at room temperature, 1 h reaction time, and sonication system, the optimal oxidation reaction of benzyl alcohol was reached when SiO2-TiO2@propylamine-Ni(II)5 was used as the catalyst in 98.52% yield.

A highly efficient supported TiO2 photocatalyst for wastewater remediation in continuous flow

Although TiO2 materials have been extensively studied as photocatalysts, there is not any commercial TiO2-supported photocatalyst used for wastewater remediation. This fact set the goal to synthesize a new supported titanium dioxide photocatalyst which, besides being robust, also has a high reaction surface and a very efficient TiO2 shell thickness. Hence, we present a novel TiO2-supported photocatalyst composed of titania-covered glass wool (GW) fibers decorated with SiO2@TiO2 core-shell spheres. For optimizing the photocatalytic activity of this material, the surface of SiO2 microspheres, as well as, the highly mechanically resistant GW fibers, were covered by a robust titania layer of ca. 20–30 nm of thickness. This layer contains nanometric crystals, ca. 12 nm in size, linked to each other and to the surfaces of both SiO2 microspheres and GW. An exhaustive characterization of the physicochemical properties of this new SiO2-TiO2 composite was performed to confirm the SiOTi linkage and the anatase crystal phase. The photocatalytic activity was initially evaluated in batch through the photodegradation of Methylene Blue as a standard dye. Afterward, the addition of the new photocatalyst in a solid phase stationary (SPS) photoreactor coupled to a TOC detector allowed studying in situ the mineralization of the recalcitrant pollutant phenol under a continuous flow regime. Results revealed that the optimized TiO2 surface of the SiO2-TiO2 composite produced the complete mineralization of phenol in less than three minutes. Even more, it was demonstrated that this photocatalyst is suitable for the industrial scale-up of wastewater treatment because it does not leach titania, its reuse does not require filtration procedures, and it can be easily implemented in SPS photoreactors at plant scale. In this context, the new material could be a good starting point to prepare other supported photocatalysts for wastewater remediation.

Clean, low-cost, and efficient nano-TiO2 composite photocatalyst: Preparation and performance in TiOSO4 hydrolysis system

Herein, SiO2-TiO2 composite (STC) photocatalysts were prepared through placing SiO2 microspheres in TiOSO4 solution and calcining at high temperature. Using STC (containing only 5.09 wt% TiO2), the degradation rate to MO with a concentration of 10 ppm was 100% at 50 min of UV illumination. The cost of the photocatalyst and the cleanliness of the preparation process were ensured due to the use of TiOSO4 as the titanium source and the water as the solvent. Therefore, not only the photocatalytic effect and application performance of TiO2 were improved, but realized the cleanliness of the preparation process and reduced the cost.

Steam reforming of biomass gasification tar over Ni-based catalyst supported by TiO2-SiO2 composite

Gasification is an important option for converting biomass into bio-syngas, but it also produces biomass gasification tar, which lowers the gasification efficiency and threatens the safety of the gasifiers. In this work, the TiO2-SiO2 composite-supported Ni-based catalyst was prepared for tar catalytic steam reforming, and its performance was systematically studied, with benzene being the model compound of tar. The results revealed that adding SiO2 to TiO2 improved the conversion of benzene and increased the yield of H2 in the syngas, which respectively reached 61.48% and 49.89 mmol/gbenzene over the 10Ni/1TiO2-0.30SiO2 catalyst, with promising thermal stability and anti-carbon deposition capacity. Furthermore, the presence of SiO2 increased the catalyst’s specific surface area and lowered the sizes of Ni crystals, thereby promoting the dispersion of active Ni sites. Meanwhile, the modification of SiO2 enhanced the catalyst’s redox ability and decreased its acidity, which suppressed the sintering of the catalyst and restricted the accumulation of carbon deposition, while the physical morphology and chemical graphitization degree of the deposits were slightly influenced. Therefore, the catalytic activity and anti-carbon deposition performance of the TiO2-SiO2 composite-supported catalyst were improved during tar catalytic steam reforming.

Polydimethylsiloxane-assisted plasma electrolytic oxidation of Ti for synthesizing SiO2-TiO2 composites for application as Li-ion battery anodes

A SiO2-TiO2 composite electrode with the synergistic effects of a stable cycle performance of TiO2 and high theoretical capacity of SiO2 was prepared through the plasma electrolytic oxidation (PEO) of Ti. When a polydimethylsiloxane (PDMS) layer is spin-coated on a Ti substrate (PDMS@Ti), the PEO reaction effectuates immediately on the pristine Ti, where the bubble phase forms first and PEO occurs for an extended period of time at a low voltage. Significantly, compared to the composite film prepared on pristine Ti, the SiO2-TiO2 composite film with a thickness of 80.39 μm exhibits large pores, which are beneficial for facilitating the transportation of Li+ with large amounts of Si. Consequently, a higher areal capacity of 1505.35 μAh cm−2 at a current density of 500 μA cm−2 was achieved compared to that of pristine Ti.

A study on the role of Ti/Si atomic ratios in the hydrodenitrogenation activity of NiMo/TiO2-SiO2 catalyst

TiO2-SiO2 composites with different Ti/Si atomic ratios were synthesized by an optimized pre-hydrolysis-co-precipitation method while the corresponding NiMo supported hydrodenitrogenation (HDN) catalysts were prepared by incipient wetness impregnation method. The significant structure of serial TiO2-SiO2 composites was determined by XRD, FT-IR, N2 physical adsorption–desorption and NH3-TPD techniques, and the distributions of TiO2 particles within SiO2 matrix were also illustrated under the help of SEM-EDS. In this work, it can be concluded that the Ti/Si atomic ratio has a large effect on the textural characteristics and the acidity distribution of composites. Among the self-made composites, TS-1 samples (Ti: Si = 1) presented the highest specific surface area (SBET = 230.42 m2/g) and the highest proportion of weak acidity. And then, characterization of the NiMo/TS-n catalysts were performed by H2-TPR, HRTEM and XPS. Among the NiMo/TS-n catalysts, NiMo/TS-1 catalysts presented the particularly favorable dispersion of active metals and the largest proportion of “Ni-Mo-S” active phase. The results of the adsorption tests showed that NiMo/TS-4 catalysts presented the maximum value of adsorption coefficient (ACQ). Compared these ACQ, these adsorption sites of quinoline were attributed to the CUS supported by “Ni-Mo-S” structures as well as the strong acid sites by excessive TiO2 particles. Finally, these catalysts were tested by feeding 1.0 wt% quinoline as the reactant under the constant reaction conditions. However, the results of HDN evaluation showed that NiMo/TS-1 catalyst exhibited the best HDN activity (51.31 %) and the highest value of turnover frequency (TOFQ = 4.77 h−1), which was attributed to the formation of maximum Ti-O-Si bonds providing moderate acidity, appropriate MSI, suitable size of MoS2 slabs and “Ni-Mo-S” active phase having high concentration of CUS and Mo-SH/S2− species.

Nature of support plays vital roles in H2O promoted CO oxidation over Pt catalysts

Pt nanoparticle catalysts supported on a series of TiO2-SiO2 composites with different molar ratios were prepared, characterized, and their CO oxidation activities were evaluated under dry and humid conditions. Among the catalysts, Pt/1Ti-3Si showed the best performance under both conditions and potentials for future industrial applications. H218O experiments were designed and the CO2 composition was calculated to quantify the promotion effect of H2O, which was highly correlated with the concentration of H2O and Ti-Si ratio. The XRD, XPS and BET results revealed that the defects on the supports inhibited phase transformation and lattice growth for anatase TiO2. These defects also led to an increase in the number of acid sites on Pt/TiO2-SiO2. The TEM, EDS mapping, and CO chemosorption results indicated that metallic Pt0 particles were formed, which was beneficial for CO oxidation during reaction. It was found that the generation of OH from H2O dissociation and the desorption of OH on TiO2 were much easier than those on SiO2, illustrating that the H2O promotion effect could be controlled by regulating the nature of support. The mechanism of H2O promotion was proposed by experimental and theoretical methods, which confirmed the carboxyl intermediate pathway rather than the formate pathway.

Block Copolymer and Cellulose Templated Mesoporous TiO2-SiO2 Nanocomposite as Superior Photocatalyst

A dual soft-templating method was developed to produce highly crystalline and mesoporous TiO2-SiO2 nanocomposites. Pluronic F127 as the structure-directing agent and pure cellulose as the surface area modifier were used as the templating media. While Pluronic F127 served as the sacrificing media for generating a mesoporous structure in an acidic pH, cellulose templating helped to increase the specific surface area without affecting the mesoporosity of the TiO2-SiO2 nanostructures. Calcination at elevated temperature removed all the organics and formed pure inorganic TiO2-SiO2 composites as revealed by TGA and FTIR analyses. An optimum amount of SiO2 insertion in the TiO2 matrix increased the thermal stability of the crystalline anatase phase. BET surface area measurement along with low angle XRD revealed the formation of a mesoporous structure in the composites. The photocatalytic activity was evaluated by the degradation of Rhodamine B, Methylene Blue, and 4-Nitrophenol as the model pollutants under solar light irradiation, where the superior photo-degradation activity of Pluronic F127/cellulose templated TiO2-SiO2 was observed compared to pure Pluronic templated composite and commercial Evonik P25 TiO2. The higher photocatalytic activity was achieved due to the higher thermal stability of the nanocrystalline anatase phase, the mesoporosity, and the higher specific surface area.

Hydrophobic agents and pH modification as comparative chemical effect on the hydrophobic and photocatalytic properties in SiO2-TiO2 coating

The SiO2-TiO2 composite has been studied through several techniques obtaining different morphologies and specific properties of SiO2 and TiO2. Nevertheless, the modification of the synthesis pH and the addition of different hydrophobic agents, such as hexamethyldisilazane (HDMS) and polydimethylsiloxane (PDMS), have not been thoroughly studied and reported. This work assessed the presence of two different hydrophobic agents and the pH modification. The SiO2-TiO2 coating was synthesized through two vias, basic and acid environment, employing the sol–gel method coupled to the sonochemistry technique. Moreover, the change of pH and use of P25 TiO2 nanoparticles and TiO2-synthesized nanoparticles allows establishing a relationship with the self-cleaning properties. The samples of SiO2-TiO2 composite were analyzed by AFM, indicating a variation in surface morphology and roughness concerning the PDMS and HMDS hydrophobic agent. ATR-FTIR analysis exhibit changes in intensity in vibrations of the Si-O, PDMS, and HMDS bonds. Raman spectroscopy results show the vibrations of the anatase and rutile phases of the TiO2 and the corresponding vibrations to the hydrophobic agents. The evaluation of self-cleaning properties demonstrated changes from the hydrophobic state to the hydrophilic state due to the addition of the nanoparticles of TiO2 to the SiO2. The photocatalytic activity was modified and improved in the HMDS-1 coating due to the hydrophobic agent and type of nanoparticles. To compare the effect of the pH in the PDMS and HMDS coatings, carried out with cyclic voltammograms and Differential Capacitance spectra. Finally, the storage time of SiO2-TiO2 coating was improved using the HMDS hydrophobic agent.

Fabrication of superhydrophilic self-cleaning SiO2–TiO2 coating and its photocatalytic performance

Generally, superhydrophilic self-cleaning coatings are prepared from semiconductors with photocatalytic properties. Organic pollutants attached to the coating surface can be degraded by its photocatalytic performance realizing a self-cleaning goal. Herein, SiO2–TiO2 composite particles were fabricated by the hydrolysis and precipitation of TiOSO4, and SiO2 microspheres were chosen as carriers, which are inexpensive and environmentally friendly. Then, superhydrophilic self-cleaning SiO2–TiO2 coatings were fabricated by spraying the composites on the surfaces of substrates. The morphology, structure and self-cleaning performance of the SiO2–TiO2 coating were characterized and tested. The results revealed that nano-TiO2 was loaded on the surfaces of SiO2 microspheres uniformly forming a hierarchical micro/nanostructure. The SiO2–TiO2 composite particles exhibited excellent photocatalytic degradation performance, and the degradation rate of methyl orange (10 ppm) was more than 98% under UV irradiation for 40 min. Furthermore, the coating prepared with the SiO2–TiO2 composite particles exhibited superhydrophilicity. A water droplet spreads completely on the coating surface in 0.35 s, and the contact angle reaches 0°. In addition, rhodamine B (RhB) and methylene blue (MB) on the coating surface can be degraded efficiently under sunlight irradiation. The SiO2–TiO2 composite particles can be sprayed directly on the surfaces of concrete, brick, wood, and glass slides. Therefore, the particles showed good adaptability to different substrates. The superhydrophilic property was due to the hydrophilicity of SiO2 and TiO2, the hierarchical micro/nanostructure of the SiO2–TiO2 composites, and the photoinduced superhydrophilicity of TiO2. The above experimental results show that the as-prepared superhydrophilic self-cleaning SiO2–TiO2 coating has a large application potential.

Effects of SiO2-based scaffolds in TiO2 photocatalyzed CO2 reduction

CO2 photoreduction has claimed as appealing process to upgrade a waste gas into valuable fuels or chemicals. Titanium dioxide (TiO2) is one of the most popular material used as catalyst for this reaction, having however a poor activity. The utilization of transparent, insulating and highly porous scaffolds to support a photoactive phase has been reported as one of the possible strategies to improve the performances of this material. In this work, two silica-based materials with different porosity type and level, were involved as support for the TiO2 and assessed in the gas-phase CO2 photoreduction with H2O. The morphological, structural and surface properties were then evaluated by means of different characterization techniques, aiming to correlate them with the catalytic activity and selectivity. The TiO2-SiO2 composites revealed a comparable activity compared to pure TiO2, despite the low fraction of photoactive phase due to improved light harvesting and reagents adsorption on the composites. The CO2 capture/photoconverting ability was evaluated, to explore the potentiality as multifunctional material.

THE EFFECT OF CALCINATION TEMPERATURE TO THE COMPOSITE CHARACTERISTICS OF TiO2SiO2 NANOPARTICLE

THE EFFECT OF CALCINATION TEMPERATURE TO THE COMPOSITECHARACTERISTICS OF TiO2SiO2 NANOPARTICLE. Self-cleaning material is a material that utilizes the photocatalytic property to degrade organic and inorganic compounds with the help of UV light. One of the materials that have good photocatalytic property is TiO2, the photocatalytic property causes TiO2 to be amphiphilic: becomes hydrophilic when there is light and becomes hydrophobic when there is no light. The photocatalytic property of TiO2 can be improved with the addition of buffer material such as SiO2. TiO2SiO2 nanoparticle was synthesized using a sol-gel method with Titanium (IV) Isopropoxide (TTIP) precursors for TiO2 and Tetraethyl Orthosilicate (TEOS) precursors for SiO2 and followed by a variation of calcination temperature of 400 °C, 450 °C, 500 °C, and 550 °C for 2 hours. TiO2SiO2 composite was synthesized using composition TiO2 sol 75% and SiO2 25%. The result of the synthesis TiO2SiO2 composite was characterized by Fourier Transform Infra-Red (FT-IR) instrument to determine the functional groups in the composites and X-Ray Diffraction (XRD) instruments to determine the phase, crystallite size and degree of crystallinity in the composite. The purpose of this research is to synthesized TiO2SiO2 nanoparticle as a self cleaning agent with variation of the calcination temperature, to obtain composite characteristics that can support self cleaning. The self-cleaning ability was based on a produced composite characteristic of TiO2SiO2. The result of FTIR characterization showed that at calcination temperature of 400 °C, 450 °C, 500 °C, and 550 °C there was a Ti-OSi bond at the peak of 948.91 cm-1, 950.77 cm-1, 941.13 cm-1, 942.13 cm-1. The result of XRD characterization showed that at the temperature of 400 °C had the best characteristics, the 75.27% anatase phase and brookite phase 24.72%. Calcinations temperature 400 °C had best degree of crystallinity of 91.66%.

Enhancing the photocatalytic activity of TiO2 and TiO2–SiO2 by coupling with graphene–gold nanocomposites

In the present paper, a novel composite Graphene–Gold (Gr–Au)/TiO2–SiO2 photocatalyst was synthesized and tested for the removal of methylene blue and rhodamine B in water solutions. First, Gr–Au nanoparticle composite was synthesized by simultaneous reduction and deposition of Au nanoparticles on Gr surface. The photodegradation of methylene blue and rhodamine B in aqueous solutions was studied using various photocatalysts, including neat TiO2–SiO2, Gr/TiO2–SiO2 and Gr–Au/TiO2–SiO2 composites. The Gr weight ratio in this research is 2% in the Gr/TiO2–SiO2 composites. Detailed characterization (field emission scanning electron microscope, Raman, Fourier transform infrared spectra and UV–vis absorbance spectroscopy) of such material was conducted. As a result, the uniform deposition of nanometer-sized Au NPs on the graphene sheets was observed. The Gr–Au/TiO2–SiO2 exhibited excellent photocatalytic efficiency because of the reduction of electron–hole recombination. The Gr2%–Au0.1%/TiO2–SiO2 composite had the highest photoactivity.

Synthesis of amorphous mesoporous TiO2-SiO2 and its excellent catalytic performance in oxidative desulfurization

Amorphous mesoporous TiO2-SiO2 composites have been prepared by introducing n-propyltriethoxysilane (PTES) into the synthesis system of titanium silicalite-1 (TS-1). The hydrolysate of PTES can participate in the condensation between ‘Si(OH)4’ and ‘Ti(OH)4’, and generate the isolated ‘alkyl-rich regions’ and ‘inorganic TiO2-SiO2 regions’. Proper amount of ‘alkyl rich regions’ can highly separate titania–silica species and seriously retard the crystal growth, thereby producing the amorphous mesoporous structure. As the PTES/Si molar ratio is between 0.1 and 0.2, the resulting samples have plenty of three-dimensional connected mesopores, and they display outstanding catalytic performance in the oxidative desulfurization of bulky sulfur compounds.

Total Hydrogenation of Furfural under Mild Conditions over a Durable Ni/TiO2-SiO2 Catalyst with Amorphous TiO2 Species.

One-step total hydrogenation of furfural (FAL) toward tetrahydrofurfuryl alcohol in continuous flow using cheap transition metals still remains a great challenge. We herein reported the total hydrogenation of FAL over Ni (∼5 nm) nanoparticles loaded on TiO2–SiO2 composites with long-term stability. The TiO2–SiO2 composites comprise amorphous TiOx which was grafted on the silica aerogel by acetyl acetone-aided controlled hydrolysis of tetrabutyl titanate. The catalysts were characterized by several techniques including Brunauer–Emmett–Teller, X-ray diffraction, transmission electron microscopy, H2-temperature-programmed reduction, and H2-temperature-programmed desorption. The hydrogenation performances were systematically explored in terms of TiO2 content, Ni loading, liquid hour space velocity, and so forth. Ni nanoparticles in contact with amorphous TiOx showed strengthened interaction with the C=O bond of FAL as well as enhanced hydrogen dissociation and desorption ability, hence benefiting the overall hydrogenation process.

Low-Temperature Preparation of SiO2/Nb2O5/TiO2–SiO2 Broadband Antireflective Coating for the Visible via Acid-Catalyzed Sol–Gel Method

Multilayer broadband antireflective (AR) coatings consisting of porous layers usually suffers poor functional durability. Based on a quarter-half-quarter multilayer structure, AR coatings with dense SiO2 film as the top layer are designed, and refractive index for each layer is optimized. After heat-treated at only 150 °C, refractive index of Nb2O5 film reaches to 2.072 (at 550 nm), which can meet design requirements of the middle layer. TiO2–SiO2 composites with controllable refractive indices are selected to be used as the bottom layer. The obtained triple-layer AR coating presents excellent performance, and the average transmittance at 400–800 nm attains 98.41%. Dense layers endow the multilayer structure good abrasion-resistance, and hexamethyldisilazane is further used to modify the surface of the AR coating, which can greatly improve the hydrophobicity of the coating. The proposed triple-layer broadband AR coating has potential value in practical applications of sol–gel deposition.

The Effect of Molar Ratios of Ti/Si on Core-Shell SiO2@TiO2 Nanoparticles for Photocatalytic Applications

After the core-shell SiO2@TiO2 nanoparticles (CSTNs) were synthesized by hydrothermal method, we investigated the influence of different molar ratios of Ti/Si on morphology, structure, and photocatalytic activity of the CSTNs. It was found that the CSTNs showed different size and surface morphology as the Ti/Si molar ratio changed. Besides, the TiO2 and the CSTN had the anatase phase after hydrothermal process and calcination at 450°C for 2 h. The N2 adsorption-desorption isotherms demonstrated the CSTNs with the molar ratio of Ti/Si increased from 1 : 1 to 8 : 1 can be categorized as type IV with hysteresis loop of type H2 and showed to be mesoporous materials. In addition, the CSTNs with the Ti/Si molar ratio of 5 : 1 had the highest surface area of 176.79 m2/g. Surface charges showed the isoelectric point (IEP) of the CSTNs ranged between silica (IEP at pH 3.10) and titania (IEP at pH 5.29). Since the molar ratio of Ti/Si increased from 1 : 1 to 8 : 1 by degradating both colorless organic pollutant of phenol and colored substances of methylene blue (MB) under UV irradiation, the photocatalytic activity of CSTNs exhibited higher photodegradation efficiency compared with TiO2. What is more, the experimental results also showed the CSTNs with Ti/Si molar ratio of 5 : 1 had the highest photocatalytic activity and showed higher photocatalytic efficiency compared with other TiO2-SiO2 composites reported for photodegradation of phenol and MB.

Immobilization of nonisolated BiPO4 particles onto PDMS/SiO2 composite for the photocatalytic degradation of dye pollutants

In this study, a crack-free PDMS–SiO2–BiPO4 (P/Si/Bi) composite was prepared via a solgel-assisted route by dispersing pre-prepared bismuth oxybromide into a solution that was composed of hydroxyl-terminated polydimethylsiloxane (PDMS–OH), tetraethyl orthosilicate and phosphoric acid. Analysis via the FTIR, XRD, XPS and SEM–EDX techniques demonstrated that the nonisolated BiPO4 particles with a monoclinic crystal phase were uniformly distributed on the surface of the P/Si/Bi composite, which can provide more active sites and a larger surface area for photocatalysis compared with other materials. The photocatalytic activity of the P/Si/Bi composite loaded with various mass ratios of BiPO4 (9 wt%, 12 wt%, 18 wt% and 27 wt%) was investigated via the degradation of methylene blue (MB, 10 mg/L) under UV light irradiation. It was found that the P/Si/Bi composite loaded with 18 wt% BiPO4 realized the highest degradation efficiency of MB, and its corresponding apparent rate constant was approximately 2.2 times that of the PDMS–SiO2–TiO2 composite (loaded with 18 wt% TiO2). The effects of inorganic ions on the degradation of MB were also investigated. The static contact angle and photocatalytic activity of the P/Si/Bi composite changed minimally after five cyclic experiments, thereby demonstrating its remarkable durability in sustainable applications. In addition, the photogenerated reactive species that were responsible for the degradation of MB within the P/Si/Bi composite were identified, and a photocatalytic mechanism was proposed.