TiO2 Spheres Research Articles

Synthesis of hollow TiO2@SiO2 spheres via a recycling template method for solar heat protection coating

The development of a simple and environmentally friendly method to synthesize hollow TiO2 structures is urgent for realizing high NIR reflectance and low thermal conductivity. Hollow TiO2@SiO2 structures have been successfully synthesized by a recycling template method. The synthesis process involves four steps as follows: 1) preparation of SiO2 spheres, 2) synthesis of SiO2@TiO2 core-shell structure by coating mesoporous TiO2 shell on SiO2 and crystallization by calcination, 3) etching the SiO2@TiO2 to form the hollow TiO2 spheres, and 4) coating the hollow TiO2 spheres with a SiO2 protection layer to produce hollow TiO2@SiO2 structures. The SiO2 serves as a template to support and synthesize hollow TiO2 shell, and then after being etched, to form a Na2SiO3 solution as a coating agent to protect TiO2 shell from photocatalytic activity. The as-synthesized hollow TiO2@SiO2 structures not only have high NIR reflectance, but also have a high thermal barrier performance due to the hollow structure. Moreover, the NIR reflectance of the coating made from hollow TiO2@SiO2 reached 94.9%, and the temperature of the inner surface of the coating board is reduced about 16 °C, compared with the surface without coating. The weather resistance studies reveal that the hollow TiO2@SiO2 sample is very stable under the UV irradiation. In particular, the hollow TiO2@SiO2 structures synthesized by using this method shows multifunctional responses towards solar heat.

Mesoporous WO3/TiO2 spheres with tailored surface properties for concurrent solar photocatalysis and membrane filtration

The strategical integration of membrane water filtration with semiconductor photocatalysis presents a frontier in deep purification with a self-cleaning capability. However, the membrane fouling caused by the cake layer of the reclaimed TiO2 nanoparticles is a key obstacle. Herein, mesoporous WO3/TiO2 spheres (∼450 nm in diameter) consisting of numerous self-assembled WO3-decoated anatase TiO2 nanocrystallites are successfully prepared via a facile wet-chemistry route. The decoration of monolayered WO3 significantly affects the surface, photocatalytic, and optical properties of original mesoporous TiO2 spheres. XRD and Raman analyses show the presence of monolayered WO3 suppresses the crystal growth of TiO2 during the calcination process, significantly improves the surface acidity, and causes an obvious red shift in absorption edge. These favorable textural properties, coupling the enhanced interfacial charge carrier separation, render mesoporous WO3/TiO2 spheres with a superior photocatalytic activity in degradation of methylene blue under UV, visible, and solar light irradiations. The optimal molar ratio of W/Ti is examined to 6%. The synthesized mesoporous WO3/TiO2 spheres also show much higher flux during membrane filtration in both dead-end and cross-flow modes, suggesting a promising photocatalyst for concurrent membrane filtration and solar photocatalysis.

Hollow TiO2 spheres wrapped in graphene nanosheets as advanced polysulfide barrier for superior electrochemical performance lithium-sulfur batteries

To meet the increasing demands of electric applications, lithium-sulfur batteries are promising energy storage systems due to their high specific capacity and energy density. However, some obstacles still hinder the practical use of lithium-sulfur batteries, which are mainly caused by the poor electronic conductivity and polysulfide migration. To deal with these problems, hollow TiO2 spheres wrapped in graphene (HTOS/G) composites are developed and used as host materials for sulfur particles. Due to the synthetic effect of improving electronic conductivity and inhibiting the polysulfide migration by employing HTOS/G as host materials, the as-prepared HTOS/G-S composites exhibit high specific capacity and excellent cycling stability. The initial specific capacity is as high as 1263 mAh g−1 at 0.1C. The HTOS/G-S composites display high capacity retention of 87.8% after 300 cycles at the current density of 2C.

Morphology-Controlled Synthesis of TiO2 with Different Structural Units and Applied for the Selective Catalytic Reduction of NOx with NH3

In our study, a series of sphere morphology of TiO2 supports owned the different structural units, including the flower-like sphere with thin-long nanorods (TiO2-75), nanosheets-assembled sphere with broad-short nanorods (TiO2-50) and particle-assembled sphere (TiO2-30) which were synthesized with adjusting volume ratio of Titanium (IV) isopropoxide/acetic acid by solvothermal method. Subsequently, CeO2–WO3/TiO2 catalysts were prepared by simple impregnation methods and applied for selective catalytic reduction of NOx with NH3. Notably, the TiO2 sphere morphology gradually varied from flower-like sphere to particle-assembled sphere with the increase volume ratio of Titanium (IV) isopropoxide/acetic acid. Meanwhile, the microscopic structural units of morphology for TiO2 support could be regularly controlled by adjusting volume ratio of Titanium (IV) isopropoxide/acetic acid. Among, the optimal flower-like sphere TiO2 morphology with thin-long nanorods had the best catalytic performance when the volume ratio was 1:75, which could be attributed to bigger pore structure and higher specific surface area supplying enough dispersion for active ingredient, adsorption of reactants and exposure of more active sites. Meanwhile, it could be found that the redox ability and abundant surface acidity of the CeO2–WO3/TiO2 catalyst played a critical role in catalytic activity via a series of characterizations.

Microstructural modification of hollow TiO2 nanospheres and their photocatalytic performance

The microstructure of photocatalysts plays a key role in enhancing their photocatalytic performance. Herein, resorcinol/formaldehyde (RF) polymer resin was prepared using the extended Stöber process and used for hard templates. Hollow TiO2 spheres (HTS) were synthesized via hydrolysis of a versatile kinetics-controlled coating and carbonization method. The physicochemical properties of as-prepared catalysts were characterized. The pure RF template had a uniform diameter of ~450 nm. By adjusting the ammonia dosage from 0.1 to 0.35 mL, monodisperse RF@TiO2 spheres were obtained with a porous TiO2 shell of ~25–160 nm in thickness. The concentration of ammonia had a significant effect on the micromorphology, and hence, the photocatalytic properties of the HTS. The Brunauer-Emmett-Teller surface area and pore volume were ~30 m2/g and 0.082 cm3/g, respectively. The intrinsically high conductivity of the HTS microspheres and their high surface area resulting from this robust hollow structure was beneficial for photocatalytic performance toward phenol decomposition.

Graphene Oxide Hybridised TiO2 for Visible Light Photocatalytic Degradation of Phenol

In industrial pollutants, phenol is a kind of degradation-resistant hazardous compound. It is generated during industrial processes in factories and treatment at sewage plants. In this study, we analyse the photocatalytic activity of TiO2 and rGO as a composite for the degradation of phenol. Hybridised titanium dioxide/reduced graphene oxide (TiO2/rGO) nanocomposites were synthesised by a simple hydrothermal method using flake graphite and tetrabutyl titanate as raw materials. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Brunauer–Emmet–Teller (BET) specific area analysis, Fourier transform infrared spectroscopy (FTIR), Raman, X-ray photoelectron spectroscopy (XPS), photoelectrochemical analysis, and UV–vis diffuse reflectance spectra (DRS) were employed to characterise the physicochemical properties of the as-prepared nanocomposites. The results showed the TiO2/rGO nanocomposites’ significant anatase phase and a small fraction of the rutile phase the same as that of the as-prepared TiO2 nanoparticles. The spherical TiO2 nanoparticles (diameter 20–50 nm) were agglomerated slightly and the agglomerates were anchored on the rGO sheets and dispersed symmetrically. The specific surface area of TiO2/rGO-4% nanocomposites was 156.4 m2/g, revealing a high specific surface area. Oxygen-containing functional groups that existed in TiO2/rGO-4% nanocomposites were almost removed during hydrothermal processing. The photocurrent response of TiO2/rGO-4% was strongest among the TiO2/rGO nanocomposites, and the bandgap of TiO2/rGO-4% was 2.91 eV, showing a redshift of absorption into the visible region, which was in favour of the high photocatalytic activity of TiO2/rGO nanocomposites under visible light (λ > 420 nm). Moreover, the samples were employed to photodegrade phenol solution under visible light irradiation. TiO2/rGO-4% nanocomposite degraded the phenol solution up to 97.9%, and its degradation rate constant was 0.0190 h−1, which had higher degradation activity than that of other TiO2/rGO nanocomposites. This is a promising candidate catalyst material for organic wastewater treatment.

Nanosheet coated dual-shell TiO2 sphere with high solar reflectance for thermal-shield materials

A dual-shell TiO2 sphere, composed of a TiO2 sphere (TS) core and SiO2 layer (SL)/TiO2 nanosheet (TNS) double shell, was prepared as a novel thermal-shield material. The high reflective rutile TiO2 core was easily synthesized via a solvothermal reaction, and then SL/TNS double shell was sequentially coated on the TiO2 core via two-step coating. This multilayer structure enhanced the solar reflectance via constructive interference between the high- and low-refractive index layers, suggesting a positive impact on potential applications as a thermal-shielding material. Moreover, the multi-faceted reflection derived from vertical growth TNS outer layer can lead to improvement in the solar reflectance caused by maximization of light scattering. As a result, it showed outstanding near infrared- and visible-reflectance value of approximately 87% and 91%, respectively, which are higher than those of neat TS and commercial TiO2.

Photocatalytic degradation of Cefazolin over spherical nanoparticles of TiO2/ZSM-5 mesoporous nanoheterojunction under simulated solar light

Abstract A nanoheterojunction photocatalyst of the spherical titanium dioxide (TSN) over ZSM-5 mesoporous was synthesized by the ecofriendly direct co-template technique with assisting of the solvent evaporation to photodegrade harmful Cefazolin compound from drinking water under simulated solar light illumination. The fabricated nanoheterojunction photocatalyst shown an efficient performance by a near-complete degrade of Cefazolin compound with an estimated efficiency of 98.5% under optimum conditions. Many parameters were considered in details, including pH solution, catalyst loading, kinetic studies, initial concentrations, optical bandgap, intermediate compounds, regeneration and the reusability. The prepared TSN@ ZSM-5 mesoporous was effectively activated in the weak acid pH region of 6.5. The data results revealed that a remarkable photodegradation of Cefazolin on the spherical TiO2 nanoparticles enhanced by the cylindrical hollow of the ZSM-5 mesoporous, which has a preferable as photogenerated delivery of the e − /h + reducing the recombination rate. High specific surface area with wide pore volume of 360 m2 g−1 & 0.42 cm3 g−1, respectively, enhanced the absorbance capacity of Cefazolin compound. The maximum absorption capacity was 1.24 mg/g under the optimum conditions. Moreover, a magnificent optical bandgap of the synthesized TSN@ ZSM-5 mesoporous was obtained. The prepared nanoheterojunction photocatalyst is well conformable the pseudo second order model and it has a high correlation coefficient of R-square is 0.9869. The data were also given by the fact that the Cefazolin compound was highly degraded with the assisting of the superoxide specie including anion radical of the •O 2 − . The Cefazolin and their intermediate compounds were decomposed to less noxious compound using the synthesized TSN@ ZSM-5 mesoporous. Although many cycles of use, the nanoheterojuncation photocatalyst was maintained its high performance with excellent durability. According to the overall results, the proposed nanoheterojunction photocatalyst can have a potential credit for participating in the wastewater treatment plant to get rid of the risk effects of the medical waste in the aqueous media.

Synthesis of Bi4Ti3O12/TiO2 Composite using Sonication Method

Composite Bi4Ti3O12/TiO2 heterojunction photocatalyst has been prepared by sonication methods. The heterojunction material Bi4Ti3O12/TiO2 was synthesized using an ultrasonic cleaning bath for 4 hours, by mixing Bi4Ti3O12 and TiO2 with variations in the comparison of mol 1:1, 1:2, 1:4 and 1:6. Characterization with XRD showed heterojunction material consisting of Bi4Ti3O12, anatase, rutile, and Bi12TiO20. The surface was observed by SEM which showed the morphology of Bi4Ti3O12/TiO2 were spherical TiO2 and plate-like Bi4Ti3O12. The band gap energy of heterojunction material with a variation in mol Bi4Ti3O12: TiO2 of 1:1, 1:2, 1:4 and 1:6 are 3.09; 3.10; 3.15; and 3.16 eV respectively. The all of band gap energy is lower than the band gap energy of TiO2 anatase and higher than the band gap energy of Bi4Ti3O12.Keywords: composite photocatalyst, heterojunction, sonochemical, Bi4Ti3O12, TiO2.

Design and fabrication of g-C3N4 nanosheets decorated TiO2 hybrid sensor films for improved performance towards CO2 gas

The g-C3N4 decorated titanium dioxide (TiO2) porous nanospheres composites thin films were successfully synthesized via a spray pyrolysis technique. The structural, morphological and textural properties of the fabricated thin film sensors were analyzed through X-ray diffraction (XRD), electron microscopy (SEM and TEM), Raman and N2 adsorption-desorption analysis. The incorporation g-C3N4 in to TiO2 matrix was also confirmed through Energy dispersive spectra (EDS) and X-ray photoelectron microspore (XPS) analysis. Gas-sensing properties of the pure and g-C3N4/TiO2 hybrid thin film sensors were investigated towards H2S and CO2 gases with various ppm levels (0–1500). The results illustrates that 10 wt.% g-C3N4 decorated TiO2 composite film show outstanding sensing response (88%) and high stability (only loss 2.5% of its initial response value) towards CO2 gas at 1500 ppm (450 °C), which is comparatively high response towards H2S gas (67%) under same ppm level. The improved sensing response is due to the incorporated g-C3N4 could provide high conductivity, large surface area (108.5 m2/g) with porous nature (15.7 nm), which is consists of interconnection between g-C3N4 nanosheets and TiO2 spheres. The improved mechanism of the proposed sensor was also discussed in detail.

Synthesis of Methyl-Capped TiO2-SiO2 Janus Pickering Emulsifiers for Selective Photodegradation of Water-Soluble Dyes.

Recently, Pickering emulsion stabilized by Janus particles has received considerable attention for interfacial reactions and droplet manipulation. However, its potential interests have been rarely explored because of the difficulties in designing and fabricating Janus particles for Pickering emulsion with suitable applications. Also, photocatalytic materials are scarcely applied as emulsifiers in Pickering emulsions because of their photogenerated hydrophilicity. This work reports the synthesis of methyl-capped Janus TiO2-SiO2 particles (MJTSs), which can be used as a novel emulsifier and photocatalyst simultaneously. The MJTSs, composed of an anatase TiO2 sphere and silica rod, are prepared by inverse emulsion-based step-by-step growth. We demonstrate that the Pickering emulsion stabilized by MJTSs represents extraordinary ability of emulsification, excellent stability, and tunable emulsion type (water in oil or oil in water). In addition, the MJTSs exhibit photocatalytic activity in decomposition of pollutants in the water phase while maintaining the stability of the Pickering emulsion.

Controllable Synthesis and Crystallization of Nanoporous TiO2 Deep-Submicrospheres and Nanospheres via an Organic Acid-Mediated Sol-Gel Process.

Although considerable progress has been achieved in the preparation of uniform hydrous TiO2 spheres (HTS) through the sol-gel process, there is plenty of room left in tailoring the size and morphology of HTS on the deep-submicron scale or even nanoscale since the diameters of the so far reported HTS are mostly on the (sub)micron scale (0.3-1.2 μm). Here, we develop a novel titanium tetraisopropoxide (TTIP)-organic acid (OA)-acetonitrile (ACN)-methanol (MeOH)-H2O system, which facilitates the control of nanoporous HTS to the range of 50-300 nm. The synthetic parameters including OA, (co-)solvent, concentration of precursor, and reaction temperature are comprehensively optimized, aiming at reproducible preparation and precise size control. Among the various OAs, n-valeric acid presents the best capability in controlling the spherical morphology and size uniformity. The synthesized amorphous HTS containing numerous micropores and mesopores show excellent hydrothermal stability and offer suitable self-template for the subsequent synthesis of mesoporous anatase TiO2 spheres (MAT) with a large surface area of 99.1 m2/g. The obtained TiO2 deep-submicrospheres and nanospheres with tunable sizes show great potential in various research fields.

Preparation of SnS2/TiO2 by a thermo-solvent ultrasonic method and its high photo-catalytic performance for decontamination under visible light

Abstract Numerous attempts have been made to develop visible-light-driven SnS2 photo-catalysts for decontamination; however, the practical application of such materials has always been limited by the rapid recombination of electrons and holes under sunlight irradiation. In this study, SnS2/TiO2 with petal-like SnS2 nanosheets grown on TiO2 spheres was successfully prepared by a simple one-step low-temperature thermo-solvent ultrasonic method. This SnS2/TiO2 could effectively utilize photon energy in sunlight and simultaneously maintain a high electron transfer rate. The SnS2/TiO2 composites showed the highest photo-catalytic activity and good stability towards decontamination (taking methyl orange as the model contaminant) compared with S2- and Sn4+ doped anatase TiO2 as well as pure TiO2 under simulated sunlight irradiation. Even if sunlight was used for irradiation (sunshine at 10 am on September 17, Beijing time, which was a cloudy day, and the temperature was 27 °C), the SnS2/TiO2 sample could still effectively degrade methyl orange (MO). In this decontamination process, MO was first reduced by the electron and then subjected to oxidation by the h+-generated ·OH. Alternatively, MO could be directly oxidized by ·OH. Apart from MO, SnS2/TiO2 composites could also be applied to effectively remove other contaminants, such as methyl blue (MB) and phenol. In summary, the prepared SnS2/TiO2 is a promising photo-catalyst for practical applications in decontamination.

Mesoporous dark brown TiO2 spheres for pollutant removal and energy storage applications

Colored TiO2 has tremendously attained significant interest worldwide due to its fascinating optical properties. Mesoporous dark brown TiO2 nanospheres with extremely high surface area (1246 m2/g) fabricated through the combined approach of thermal annealing with the sol–gel method. FESEM images inferred the creation of the spherical structure of 357 nm which transformed into defected mesoporous TiO2 spheres of 452 nm under annealing at 350 °C. UV-DRS PL and EPR studies confirm the bandgap narrowing due to the creation of oxygen defects sates in the TiO2 sample. Dark brown TiO2 exhibits remarkable sunlight-induced photodegradation activity for methylene blue and oxytetracycline hydrochloride molecules. Mesoporous TiO2 defect rich spheres adsorb the 32% of the MB pollutant molecules in just 30 min. Moreover, it decomposes the rest 67% of 15 µM MB dye solution and 0.5 mg/mL OTC solution in 30 min and 80 min respectively. Existences of high oxygen defect states in TiO2 were responsible for the bandgap narrowing and improve charge carriers separation and superior photocatalytic activity (PCA). Mesoporous dark brown TiO2 sample was also investigated for the energy storage application. Unusual high surface area also facilitated the accumulation of charges and led to the enhancement in charge storage properties.

Tailoring TiO2 through N doping and incorporation of amorphous carbon nanotubes via a microwave-assisted hydrothermal method

Abstract Nanohybrids consisting of titanium dioxide (TiO2) and amorphous carbon nanotubes (aCNTs) or amorphous nitrogen-doped carbon nanotubes (aNCNTs) were synthesized using the microwave radiation-assisted hydrothermal method in order to investigate the effect of CNTs on the physicochemical, optical and photocatalytic properties of doped and undoped TiO2. The synthesized nanohybrids consisted of titania–aCNT (TiO2–aCNT), titania–aNCNT (TiO2–aNCNT), and nitrogen doped titania–aNCNT (NTiO2–aNCNT). Pristine NTiO2 was also synthesized as a control. It was observed that a small amount of aCNTs and aNCNTs (3 wt.%) causes a significant difference in the physicochemical properties of the TiO2 nanohybrids such as particle size, particle size distribution, aggregation and optical properties. The presence of aNCNTs and aCNTs improves particle dispersion, reduces particle size and the size distribution for both TiO2 and NTiO2. In addition, aCNTs or aNCNTs promote the formation of spherical TiO2 and cuboidal NTiO2 nanoparticles as opposed to the nanosheets in NTiO2. Both carbonaceous materials also suppress electron-hole recombination, thus enhancing the photocatalytic activity of the nanohybrids. A strong correlation between the CNT loading and the physicochemical, optical properties and photodegradation of Congo Red dye of the nanohybrids was observed. For example, the nanohybrid TiO2–aNCNT exhibited the smallest particle size and size distribution (6.18 ± 1.25 nm), the lowest energy band gap (3.02 eV) the lowest PL intensity and thus the highest photocatalytic efficiency (99.2 % in 30 min with k 1 a p p = 41.2 × 10 - 3 m i n - 1 ) with TiO2–aCNT being the second best in terms of particle size (7.06 ± 1.48 nm), energy band gap (3.04 eV) and hence the CR removal rate at 30 min (99.8 %). Furthermore, a comparison of the least performing photocatalyst NTiO2 and NTiO2–aNCNT shows that while the incorporation of aNCNT into NTiO2 increases the energy band gap from (3.15–3.19) eV, it still enhances the NTiO2 particle dispersion and reduce the PL intensity. As a result, NTiO2 has less overall removal of CR 63.3 % than NTiO2–aNCNT (82.6 %). Lastly, the incorporation of the carbonaceous materials promotes the second order adsorption kinetics and improves the photocatalytic performance of the nanohybrids.

Structure-dependent adsorptive or photocatalytic performances of solid and hollow dendritic mesoporous silica & titania nanospheres

Abstract Two types of titania-containing dendritic mesoporous silica nanospheres (DMSNs) have been successfully fabricated for organic dyes removal, water splitting, and carbon dioxide reduction by their adsorptive or photocatalytic performances. Hybrid dendritic mesoporous silica&titania nanospheres (DMSTNs) were initially prepared by grafting tetrabutyl orthotitanate (TBOT) onto DMSNs. Then, hollow dendritic mesoporous silica&titania nanospheres (HDMSTNs) were realized merely by etching the solid DMSTNs with alkaline solution. The surprising structural evolution from the solid state to the hollow was thoroughly revealed by scanning electron microscope (SEM) and high resolution transmission electron microscopy (HRTEM) for the first time. DMSTNs maintain the dendritic morphology with spherical TiO2 nanoparticles uniformly dispersed. HDMSTNs not only keep the dendritic topology, but also possess the hollow texture with TiO2 nanoparticles unevenly dispersed and aggregated. DMSTNs and HDMSTNs exhibit excellent adsorption capacities for methylene blue, while the latter shows improved adsorption capacity. DMSTNs and HDMSTNs can hardly adsorb methyl orange (MO), nevertheless, the two materials can photodegrade MO with outstanding abilities. Amazingly, the latter exhibits decreased degradation capacity despite of its hollow architecture and higher content of titanium oxide. Furthermore, DMSTNs and HDMSTNs display higher photocatalytic activities over hydrogen generation than that of carbon dioxide reduction under visible light. However, DMSTNs and HDMSTNs show various photocatalytic selectivities and activities for the production of carbon monoxide (CO) and methane (CH4). In short, DMSTNs and HDMSTNs have distinct structural superiorities as adsorbents or photocatalysts for different photocatalytic reactions, respectively.

Hierarchical Flower-Like Hollow SiO2@TiO2 Spheres with Enhanced Thermal Insulation and Ultraviolet Resistance Performances for Building Coating.

In this paper, a novel 3D hierarchical flower-like hollow SiO2@TiO2 sphere (FHST) with a large number of irregular nanosheets was successfully prepared by a solvothermal method and subsequent calcination process, in which multiple different functional components were perfectly integrated into a single nanostructure. The morphology and structure of FHSTs were characterized by SEM, TEM, XRD, XPS, and BET. The growth mechanism of the 3D flower-like structure was obtained through a series of single-factor experiments, of which hexamethylenetetramine acted in a vital role. Moreover, it was also used as a filler for polyacrylate substrate to improve the thermal insulation and ultraviolet resistance properties of architectural coatings. The results showed that the composite film with FHSTs had lower thermal conductivity and higher light reflection performance compared to those with hollow SiO2 spheres, hollow TiO2 spheres, and hollow SiO2@TiO2 spheres. More significantly, its transmittance at the full wavelength of ultraviolet light was almost zero, exhibiting a prominent inhibitory effect on UVA. In addition, compared with commercially available hollow glass microspheres, FHSTs had more excellent thermal insulation performance in practical applications.

Ultraviolet-Induced Interfacial Crystallization of Uniform Nanoporous Biphasic TiO2 Spheres for Durable Lithium-Ion Battery

Porous TiO2 has been widely studied as an anode material of lithium-ion battery, most of which, however, are crystalline with a limited surface area (e.g., 50–120 m2/g) and a large pore size of 10–20 nm greatly exceeding the ion radium of Li+ ion and its complexes. Herein a facile UV-induced interfacial crystallization method is developed for the sol–gel-derived amorphous hydrous TiO2 spheres (HTS) at ambient condition. Tuning the dispersant (e.g., ethanol, H2O, methanol, or their mixture) and the wavelength of the light source allows for selective control over the crystal phase of anatase, rutile, or their biphase formed at the spherical surface, although the total crystallinity remains poor. The optimal nanoporous biphasic TiO2 spheres of anatase and rutile upon 254 nm UVC irradiation of HTS in H2O and methanol mixed solution for 4 h exhibit an ultralarge surface area of 358.1 m2/g and comprise numerous micropores and small mesopores (∼3.31 nm), rendering the fabricated LIB with high current density, rate capacity, cycle performance, and Li+ transfer rate. A superior electrochemical reversible specific capacity of 128.6 mAh/g can be attained over 1000 cycles of charge/discharge processes at 1C rate. Our simple and general synthesis strategy is promising for the rational design of various photostable materials with improved crystallinity, tunable crystal phases, large surface area, and applicable pore size.

Spatially Separated Bifunctional Cocatalysts Decorated on Hollow-Structured TiO2 for Enhanced Photocatalytic Hydrogen Generation.

Efficient charge separation can promote photocatalysis of semiconductors. Herein, a hollow-structured TiO2 sphere decorated with spatially separated bifunctional cocatalysts was designed, which exhibited enhanced photocatalytic hydrogen generation. Ultrasmall-sized MOx (M = Pd, Co, Ni, or Cu) nanoparticles (NPs) were first introduced into a zeolite via confinement synthesis, and then, hollow TiO2 was fabricated by using the zeolite as a sacrificial template forming MOx@TiO2. Finally, Pt NPs were decorated on the outer shell, giving rise to MOx@TiO2@Pt, in which the MOx NPs and Pt NPs acted as hole capturers and electron sinks, respectively. Thanks to the enhanced light harvesting of the hollow structure and improved charge separation induced by the smaller-sized cocatalysts as well as spatially separated bifunctional cocatalysts, the as-prepared PdOx@TiO2@Pt catalyst exhibited a superior photocatalytic hydrogen-generation property (0.45 mmol h-1). This work demonstrates the advantage of the spatially separated bifunctional cocatalysts in enhancing the photocatalytic properties of semiconductors.

A three-dimensional TiO2-Graphene architecture with superior Li ion and Na ion storage performance

In this work, a three-dimensional TiO2-graphene composite with large specific surface area is designed by freeze drying. In this architecture, primary TiO2 nanoparticles (less than 10 nm in size) are wrapped with graphene homogeneously, forming spherical secondary particles (≈100 nm), and the spherical TiO2 particles further agglomerate into platelet-like particles with several micrometers in size. The TiO2-graphene composite delivers high de-lithiation and de-sodiation capacities of 312 mAh g−1 and 280 mAh g−1 at 17 mA g−1 as negative electrode materials in lithium and sodium cells, respectively, and excellent cycling performance with negligible capacity loss after 500 cycles at a specific current of 85 mA g−1. When coupled with an activated carbon positive electrode, it demonstrates high capacitance and long cycle life in sodium ion capacitors (81% after 2000 cycles at 1 A g−1) and lithium ion capacitors (95% after 5000 cycles at 1 A g−1). Its superior performance benefits from the designed 3D architecture, which combines the advantages of small primary particle size, a homogeneous carbon coating and an adequate contact area with the liquid electrolyte. The storage mechanisms of the superior TiO2-graphene composite in lithium and sodium cells are investigated by operando X-ray diffraction studies.