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Sacrifiers-promoted photocatalysis is a useful way to achieve high efficiency photoreduction and photocatalytic hydrogen production for photocatalysts of weak reductive power such as TiO2. Herein we report a new method to fabricate a unique dyadic hybrid consisting of closely compacted crystalline (anatase) and titanium glycerolate (TiG)-derived organic group-retained amorphous nanoparticles to validate adsorption-stored sacrifiers-promoted photocatalysis instead of using sacrifiers in bulk solution. It was found that ascorbic acid (AA)-modified TiG prepared at a small fraction of glycerol, characterized by peculiar cocoon/open nanocontainer-type morphologies, varieties of oxygen containing groups, and remarkably high specific surface area, is suitable for precursing such hybrids. AA can change crystallization processes and particle morphologies by terminating chain linkages in TiG structure, which increases porosity and brings about visible light responsive photocatalysis for the dyadic hybrid. Benefiting from good adsorption affinity to organic sacrifiers, the sacrifier-prestored hybrid can catalyze significantly enhanced photoreduction with good reproducibility toward dye molecules via the synergy of sacrifier enrichment and photocatalysis. AA modified TiG also exhibits good self-reducibility enabling pre-loading of highly dispersed and localized platinum nanoparticles, and the resulted dyadic hybrid facilitates photocatalytic hydrogen production of extremely higher turn-off frequency and better impurities interference-resistivity compared to the P25-based commercial catalyst.

Gas sensors have become increasingly significant because of the rapid development in electronic devices that are applied in detecting noxious gases. Adjusting the crystal phase structure of sensing materials can optimize the band gap and oxygen-adsorptive capacity, which influences the gas sensing characteristics. Therefore, titanium dioxide (TiO2) materials with different crystal phase structures including rutile TiO2 nanorods (R-TiO2 NRs), anatase TiO2 nanoparticles (A-TiO2 NRs) and brookite TiO2 nanorods (B-TiO2 NRs) were synthesized successfully via one-step hydrothermal process, respectively. The gas sensing characteristics were also investigated systematically. The sensors based on R-TiO2 NRs displayed the higher response value (12.3) to 100 ppm acetone vapor at 320 °C compared to A-TiO2 NRs (4.1) and B-TiO2 NRs (2.3). Furthermore, gas sensors based on R-TiO2 NRs exhibited excellent repeatability under six cycles and good selectivity to acetone. The outstanding sensing properties of gas sensors based on R-TiO2 NRs can be ascribed to relatively narrow band gap and more oxygen vacancies of rutile phase, which showed a probable way for design gas sensors based on metal oxide semiconductors with remarkable gas sensing performances by the crystal phase adjustment engineering in the future.

The construction of a Z-scheme photocatalyst by coupling semiconductors with conductors is an efficient way to achieve high pollutant degradation efficiency. In this study, a hydrothermal approach was used to fabricate a Z-scheme photocatalyst consisting of C-MoS2 sheets wrapped around octahedral anatase TiO2 nanocrystals. The catalyst showed excellent photocatalytic efficiency (99%) for methylene blue degradation with low catalyst loading (0.2 g L-1) under the simulated solar light within 60 min. High photocatalytic degradation efficiencies were also observed for Rhodamine B, methyl orange, and tetracycline under solar irradiation. The C-MoS2 acts as an electron mediator and serves as a carrier transmission bridge for the efficient electron-hole separation. The electron-rich (1 0 1)-faceted TiO2 benefits the Z-scheme recombination of electrons from the conduction band of TiO2 and holes at the valence band of MoS2. The semiconductor coupling of (1 0 1)-exposed octahedral TiO2 and 2H-MoS2 as well as the introduction of solid-state electron mediators, 1T-MoS2 and carbon, resulted in increased light absorption and accelerated charge transfer at the contact interface, which enhanced the photocatalytic activity of the photocatalyst significantly compared to those of P25, MoS2/TiO2, and C-MoS2. The efficient separation of electron-hole pairs prolongs their lifetime for oxidation and reduction reactions in the degradation process.

Owing to the unique electronic properties of layered materials, topological insulators have interestingly grabbed much attention in the field of photocatalytic water splitting. Nowadays, 2D layered materials were composited with semiconductor photocatalysts, encourage much as it provides enormous active sites and also significantly prevent photogenerated charge recombination. Especially, Bi2Se3 possesses exceptional properties like topologically preserved conducting surface states with bulk insulating behavior and high surface area, which provides unconventional electron dynamics, resulting in facile electron transport and effective charge separation to photocatalyst. So far, several methods have been attempted to synthesize few-layered Bi2Se3 nanosheets from its bulk crystals. Here, a unique attempt is made and succeeded to exfoliate bulk Bi2Se3 to few layered nanosheets via surfactant free supercritical fluid processing using N-Methyl-2-pyrrolidone (NMP) as an exfoliating agent, with a short reaction time of 15 min. The exfoliation of Bi2Se3 crystal was confirmed by several characterization techniques, such as XRD, SEM, Raman, and HR-TEM. Furthermore, different weight percentages of exfoliated Bi2Se3 sheets/anatase TiO2 nanoparticles were prepared and examined the photocatalytic activity using glycerol as a hole scavenger. Among them, 15 wt.% Bi2Se3 coupled TiO2 nanocomposite showed enormous hydrogen evolution rate of 84.9 mmol h-1g-1cat, which is 80 times higher than that of TiO2 nanoparticles. In addition, the photostability of the nanocomposite was also verified, where it retains 94% of activity even after 4 cycles of continuous experiments. The improved rate of H2 production was understood by theoretical calculations that topologically preserved conducting surface states of co-catalyst, Bi2Se3 nanosheets is supported to high mobile and scatter free electrons. It mediates the transport of electrons with TiO2 nanoparticles that helped the effective charge separation. Thus, it proves a promising candidate for photocatalytic hydrogen production.

TiO2 nanostructures have been one of the most explored metal oxides photocatalysts to apply for environmental remediation. However, its wide band gap results in the underutilization of sunlight for degradation of pollutants. In order to overcome this handicap, the synthesis of TiO2-based composite has brought extraordinary materials. In this study, we design and prepare TiO2/Nb2O5 heterostructures with different molar ratios by using peroxotitanium and peroxoniobium complex as precursors in aqueous solution. The TiO2 exists in the form of anatase while Nb2O5 is amorphous in the composite, leading to a special crystalline TiO2/amorphous Nb2O5 heterostructures. In particular, Nb element is also doped and Ti3+ ions are formed in the TiO2 lattice, leading to a reduced band gap. The unique TiO2/0.25Nb2O5 (Ti:Nb = 2:1) heterostructures can effectively suppress the recombination of photogenerated electrons and holes, and facilitate the charge transfer, resulting in the optimum photocatalytic performance. The nitrogen oxide removal efficiency by TiO2/0.25Nb2O5 is 77.23% in visible light, which is 3.8-folds and 7.0-folds higher than pure TiO2 and Nb2O5. Photocatalytic degradation of acetaminophen by TiO2/0.25Nb2O5 is 90.6% in visible light, which is approximately 2.5-folds higher than pure TiO2 and Nb2O5.

CuO supported catalyst with high valence rhenium doping were specially studied for photoelectrocatalytic reduction of CO2 to small molecular alcohols, which were synthesized by nitrate thermal decomposition method on anatase TiO2 nanotube arrays (TiO2-NTs). Photoelectrochemical measurements indicate that the high valence rhenium doping helps in improving the catalytic activity and selectivity of CuO supported catalysts. For the case of 6 wt% Re-doped CuO/TiO2-NTs calcined at 723 K, the principal products are methanol and ethanol with yield up to 19.9 μmol and 7.5 μmol after 5 h photoelectrocatalysis at external potential of −0.4 V under simulated solar illumination. In contrast, the products catalyzed by undoped CuO/TiO2-NTs are only methanol and formaldehyde. These results indicate that the high valence rhenium doping will promote the alcoholization process and benefit the C C coupling, leading to the selective conversion of CO2 to ethanol. Furthermore, under suitable external potential (-0.5 V) the CO2 conversion product is almost entirely composed of ethanol.

In comparison to the common anatase, rutile and brookite phases, the bronze phase TiO2 (TiO2(B)) is rarely prepared, and obtaining unique TiO2(B) structures, especially those with complex configurations remains a great challenge. This work presents a completely new synthetic approach for fabricating hierarchical nanoporous TiO2(B) assemblies with tailored crystallites and architectures via the reaction between tetrabutyl titanate and normal fatty acids. Three different kinds of normal fatty acids, i.e., pentanoic acid, hexanoic acid, and nonanoic acid were utilized as the sole solvent. After a simple solvothermal treatment, nanoporous TiO2(B) microspheres constructed by [0 0 1]-elongated ultrathin nanorods, randomly aggregated ultrafine nanocrystals, and crystallographically oriented nanocrystals were successfully produced separately. Further investigation revealed that the morphology of the hierarchical assemblies could be modified by using foreign substrates to adjust the growth dynamics of TiO2(B) crystals. As a good illustration, by introducing graphene nanosheets into the tetrabutyl titanate-pentanoic acid system, nanosized [0 0 1]-elongated-ultrathin-nanorod-constructed nanoporous TiO2(B) assemblies were obtained, which exhibited superior performance as an anode in Li-ion batteries. This work can not only shed new light on TiO2(B) crystallization, but also provide an effective solution for the rational design of complex TiO2(B) micro-/nanoarchitectures for desired applications.

Environmental remediation via semiconductor (SC) photocatalysis has attracted great attention over the past three decades. However, prospect for large scale application is still under debate, basically due to the bottleneck of fast charge recombination and/or slow surface reaction. Herein we report a universal solution of speeding up organic degradation simply via co-deposited Pt and nickel phosphate (NiP). Several representative SCs have been examined, including TiO2 (anatase, rutile, and brookite) under a 320 nm light, and Bi-based SC (BiVO4, Bi2WO6, and Bi2MoO6) under a 420 nm light. In all cases, the rates of phenol degradation in aqueous solution always varied not only in the order of NiP/Pt/SC > Pt/SC > NiP/SC > SC, but also NiP/Pt/SC > (Pt/SC + NiP/SC + SC). Meanwhile, hydroquinone and benzoquinone were produced as the main intermediates, but their concentration was much lower than that of phenol decreased, especially for NiP-containing sample. The solid was characterized with several techniques, including photoluminescence and (photo)electrochemical measurement. It is proposed that Pt and NiP act as co-catalysts for O2 reduction and phenol oxidation, respectively. Such electron and hole transfer promote each other, additionally improving the efficiency of charge separation, and further increasing the rates of surface reactions. This work highlights the necessity of a versatile co-catalyst in SC photocatalysis.

Constructing effective interphase boundary is one of the efficient approaches for improving photocatalytic performances of semiconductor materials. In this work, an anatase/rutile-TiO2 (AR-TiO2) heterophase junction with appropriate carbon content was successfully fabricated via an in-situ phase transformation process. The phase transformation started from the inner core of the nanoparticles and the area of phase interface between anatase and rutile was carefully controlled by regulating the activation temperature. The well-established type-II band alignment between two TiO2 phases with residual carbon as additional charge transfer intermediary which significantly improved the light-harvesting and photoinduced electron-hole pair separation. As a result, the optimal AR-TiO2-550 catalyst (without adding commonly used Pt as co-catalyst) remarkably enhanced photocatalytic H2 generation (201 μmol h−1 g−1), which was about 12-fold to that of P25. The AR-TiO2-550 heterophase junction also showed long-term stability under simulated solar light irradiation. This research provides a new phase engineering route for developing high-efficient photocatalysts.

The oxide-based hybrid photocatalysts, especially TiO2-based, have attracted tremendous attentions because of their prominent photocatalytic performance. Currently, theoretical understandings on the relationship between the interface of TiO2-based heterostructures and their photocatalytic activity are still lacking. Here we systematically investigated the effects of interface structure on electronic properties of the g-C3N4/TiO2 heterostructure using density functional theory (DFT) calculation. The interaction between monolayer g-C3N4 and TiO2 surface [with Anatase (1 0 1)/(0 0 1) facet] was explored, where a van der Waals heterojunction is formed. The presence of oxygen vacancy, nitrogen doping and hydrogen passivation on TiO2 surface is found to dramatically alter the electronic properties of g-C3N4/TiO2 heterostructure. Furthermore, the enhanced separation of electron − hole pairs and inhibited carrier recombination in the g-C3N4/TiO2 interface was analyzed based on the Bader charge analysis and charge density difference. The theoretical analysis revealed that oxygen vacancy and hydrogen passivation on TiO2 A001 surface induces the more significant charge separation, which may be the origin of enhanced photocatalytic efficiency of the g-C3N4/TiO2 heterostructures.

Titania (TiO2) supported iron oxides (Fe-TiO2) are ideal catalysts to be applied in heterogeneous photo-Fenton oxidation (HPFO) for wastewater treatment because of the capabilities of TiO2 in photocatalysis and iron oxides in interfacial H2O2 activation. It is important to understand the influences of the structural parameters of Fe-TiO2 catalysts and the complicated interplay between TiO2 and iron oxides on the performance of HPFO. In this paper, a series of Fe-TiO2 catalysts are obtained through a facile solid-phase synthesis method. The iron loading content and the calcination temperature are systematically adjusted to tune the crystal phase, size, anatase/rutile ratio and density of oxygen vacancy (OV) site of TiO2, the dispersing state of iron species, and the interfacial structure of the Fe-TiO2 catalysts. Then, the performance of these catalysts in HPFO for degrading methylene blue (MB) are comparatively studied. Correlations between the performance and various structural properties of the catalysts are clarified. The interplay between TiO2 and iron oxides in the HPFO process is elucidated. The insight reaction mechanism is also discussed. Under optimized conditions (an iron loading of 1 wt% and a temperature of 600 °C), Fe-TiO2 catalysts with iron lattice doping, well-dispersed ultrasmall α-Fe2O3 nanoparticles, appropriate anatase/rutile ratios and abundant OV sites can be obtained. The anatase-rutile-Fe2O3 heterojunction, ultrasmall α-Fe2O3 nanoparticles and OV sites in the optimized catalysts work synergistically to improve the charge migration and interfacial activation of H2O2, leading to superior HPFO performance for MB degradation and mineralization.

Anatase/rutile titanium dioxide (TiO2) with heterophase junction and large Brunauer-Emmett-Teller (BET) specific surface area (50.1 m2 g−1) is successfully synthesized by calcinating Materials of Institut Lavoisier-125(Ti) (MIL-125(Ti)) with 30% O2/Ar at the temperature of 600 °C (M−O−600). Several techniques are used to examine the physicochemical, photoelectrochemical and optical properties of samples, and their photocatalytic performances are evaluated by photodegradation of gaseous toluene and liquidus tetracycline (TC) under visible light illumination. It is found that the calcination temperature has significant influence on the crystal structure and physicochemical parameters of TiO2. The weight fractions of rutile and anatase TiO2 of M−O−600 are approximately 0.7 and 0.3, which displays outstanding photocatalytic activity. Through the construction of heterophase junction, M−O−600 has better oxygen adsorption and higher density of localized states, which effectively promotes the generation of superoxide radical (·O2–) and hydroxyl radical (·OH) species. In-situ infrared spectra indicate that toluene is oxidized to benzyl alcohol, benzaldehyde and benzoic acid in turn and then oxidized to formic acid and acetic acid before eventually degraded into H2O and CO2. Gas chromatography-mass spectrometry (GC–MS) is also used to further investigate the degradation pathway of toluene. Degradation pathway and mechanism of TC are studied by liquid chromatography-tandem mass spectrometry (LC-MS). Moreover, three-dimensional excitation-emission matrix fluorescence spectroscopy (3D EEMs) and total organic carbon (TOC) show that TC can be effectively mineralized through a series of reactions by M−O−600 during photocatalysis.

The low charge separation efficiency and sunlight utilisation of traditional titanium dioxide (TiO2) nanoparticle photocatalysts greatly limit their applications. Herein, one-dimensional (1D) mesoporous anatase TiO2 nanotubes with engineered surface defects are fabricated using a combination of simple solvothermal synthesis and high-temperature surface hydrogenation strategy. The obtained mesoporous anatase TiO2 nanotubes with mesopores in the nanotube walls and a specific surface area of 110 m2 g−1 decrease the bandgap from 3.18 to 2.98 eV, enhancing the photoresponse to the visible-light region of the solar spectrum. The defective mesoporous anatase TiO2 nanotubes exhibited an excellent photocatalytic hydrogen evolution rate of 9.8 mmol h−1 g−1, which is approximately 2.5 times higher than that of the pristine anatase TiO2 nanotubes. This can be ascribed to the engineered surface defects and 1D mesoporous nanotube structure favouring efficient spatial charge separation on the horizontal–vertical dimensions, enabling visible-light absorption and exposing abundant surface active sites. This study provides a facile and feasible strategy for the fabrication of high-performance 1D mesostructured semiconductor oxide photocatalysts for efficient solar energy conversion.

Studies on photocatalytic activity of monophasic and biphasic TiO2 have been well explored. However, detailed studies on the photocatalytic activity of triphasic titania, as opposed to monophasic or biphasic TiO2 are scarce. Here we report a comparative structure-sensitive photocatalytic study of triphasic versus anatase TiO2, both have been synthesized under near-identical conditions through a customized sol–gel approach. The composition of the phases is tuned just by varying the thermal pre-treatment conditions of TiO2 gel that has been subsequently subjected to calcination at 300 °C. Interestingly, when the pre-treatment temperature of the gel is systematically increased from 50 to 250 °C, a transition from anatase to triphasic (anatase, rutile, and brookite) and then again to anatase has been observed. The synthesized TiO2 phase compositions have been thoroughly characterized for their structural, optical, electrical, surface and morphological properties. Among the different phase compositions, triphasic titania having a significant proportion of rutile has been found to exhibit the highest photocatalytic activity, as probed using model organic pollutants, Methylene Blue (MB) and 4-Chlorophenol (4-CP). In addition to the earlier known factors such as effective heterojunction, and favorable position of the valence band (VB), an important contribution to the high photocatalytic activity of triphasic TiO2 has been experimentally found to stem from the additional electron density in VB that is attributed to the lattice contraction of anatase phase owing to the coexistence of other two phases. The study provides fundamental insights into the energetics that impact the photocatalytic activity of triphasic versus anatase TiO2.

Solar-driven CO2 photoreduction into fuels has great potential in addressing the environmental and energy crisis. Heterophase TiO2 has attracted increasing attention in photoenergy applications owing to its fascinating properties, but much more attention has been paid on photodegradation and photocatalytic water splitting than that of photocatalytic CO2 reduction. Herein, anatase–rutile heterophase TiO2 nanoparticles with oxygen vacancy (TiO2-x) were successfully synthesized by involving proper amounts of polyols (EG, DEG, TEG, etc.) into the reaction system. The heterophase TiO2-x nanoparticles could accelerate the electron-hole separation and exhibit superior photocatalytic activity for reducing CO2 into methane. This work offers an alternative approach to simply fabricate TiO2-x-based heterophase photocatalyst towards efficient CO2 photoreduction.

The electrochemical reduction of carbon dioxide and nitrite ions into value-added chemicals represents one of the most promising approaches to relieve the greenhouse gases, while a critical challenge is to search for a highly effective catalyst with low energy input and high conversion selectivity. In this work, we demonstrated low-valence Cu doped, oxygen vacancy-rich anatase TiO2 (Cu-TiO2) nanotubes as a synergetic catalyst for electrochemical co-reduction of both CO2 and NO2–. The incorporation of Cu dopants in anatase TiO2 facilitated to form abundant oxygen vacancies and bi-Ti3+ defect sites, which allowed for efficient nitrite adsorption and activation. The low-valence Cu dopants also served as effective catalytic centers to reduce CO2 into CO* adsorbate. The close proximity of CO* and NH2* intermediates was beneficial for the subsequent cooperative tandem reaction to form urea via the C N coupling. This oxygen vacancy-rich Cu-TiO2 electrocatalyst enabled excellent urea production rate (20.8 μmol⋅h−1) and corresponding Faradaic efficiency (43.1%) at a low overpotential of –0.4 V versus reversible hydrogen electrode, substantially superior than those of undoped TiO2, thus suggesting an exciting approach for cooperative CO2 and nitrogen fixation.

The uniform tablet-like TiO2/C nanocomposites with two crystal types (rutile and anatase) and large specific surface area (438 m2 g−1) were successfully prepared by Materials of Institut Lavoisier-125(Ti) (MIL-125(Ti)) calcined at a suitable temperature and applied for photocatalytic tetracycline (TC). The nanocomposites were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and mapping, N2 adsorption-desorption isotherms, photoluminescence spectra (PL), photocurrent, and X-ray photoelectron spectroscopy (XPS). The changes of physicochemical parameters are discussed in detail. It is found that nanocomposite through suitable calcination temperature (M-A-800) with large surface area and appropriate micropore/mesopore ratio could strengthen separation and migration rates of photo-generated charge, resulting in the improvement of visible light photocatalytic activity of tetracycline, and exhibited about 2.0 times quicker than that of MIL-125(Ti). In addition, M-A-800 displayed favourable reusability and stability in four circulation tests. Finally, the reaction mechanism of photocatalyst and photodegradation pathway of tetracycline was also proposed. O2− was the most important active species, and dehydroxylation and decarboxylation were the main photodegradation pathway of tetracycline.

Herein, we report surface coarsened titanium dioxide (TiO2) nanobelts with anatase/rutile heterophase junctions via a facile hydrothermal/calcination method for simultaneous hydrogen (H2) and oxygen (O2) productions from pure water, with excellent production rates of 0.614 and 0.297 mmol h−1 g−1 with platinum (Pt)/cobalt phosphide (CoP) as cocatalysts, respectively. Besides, the TiO2 nanobelts-900 °C with anatase/rutile heterophase junctions show a notable improvement in photocatalytic H2 and O2 production than pure anatase TiO2 nanobelts (TiO2 nanobelts-600 °C, 700 °C and 800 °C) and pure rutile TiO2 nanobelts (TiO2 nanobelts-1000 °C). The anatase/rutile heterophase junctions could effectively stimulate the transfer of electrons from rutile to anatase and then to Pt, and H2 generation on the surface of Pt. In the meantime, the holes can be transferred from anatase to rutile and then to CoP, and water oxidation on CoP’s surface.

TiO2 nanosheet/NiO nanorod heterojunction hybrids have been developed through a hydrothermal route, where NiO nanorods (size: 5 nm in diameter and 20–40 nm in length) are deposited at the {0 0 1} facet of anatase TiO2 nanosheets. The photocatalysts were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD), N2 adsorption-desorption analysis, UV–vis spectroscopy, X-ray photoelectron spectroscopy (XPS), photoluminescence spectroscopy and time-resolved fluorescence. The TiO2/NiO photocatalysts exhibited good photocatalytic activities towards the degradation of methyl blue (MB) and phenol, and hydrogen generation efficiency under visible light irradiation. The maximum rate constant can be reached 0.0279 min−1 and 0.0135 min−1 respectively, which are about 12 and 10 times higher than that of TiO2 nanosheets. And the hydrogen generation efficiency is 10 times higher than physical mixing of TiO2 and NiO. Photocatalytic degradation efficiency remains more than 90% after 6 times cycle dye degradation, and the H2 production efficiency is almost the same after four cycles, suggesting good stability and reusability. The enhanced photocatalytic activities are associated with the rational design of TiO2/NiO hierarchical heterojunctions which ensues high photogenerated charge separation efficiency. With the improved photocatalytic performance, the TiO2/NiO heterojunction hybrids are expected to be potential photocatalysts in environmental and energy related areas.

Semiconductor photocatalysis has long been considered as a promising approach for remediation of polluted water. However, the high recombination rate of electrons and holes, as well as a low reaction rate, have impeded its large-scale applications. Therefore, it is of great importance to develop appropriate photocatalysts for promoting its practical application. In this study, a novel TiO2/SiO2/carbon electrospun nanofiber mat (TSC NFM) with flexibility and porous hierarchy has been successfully designed and fabricated by a facile method of electrospinning and carbonization. Characterization results show that the TSC NFM consists of closely-packed and well-distributed anatase (TiO2) nanocrystals, amorphous SiO2 nanoparticles, and carbon with interconnected meso- and macro-pores. The photocatalytic performance of the TSC NFM was evaluated by degrading rhodamine B and 4-nitrophenol in batch systems. The results show that TSC NFM exhibits a higher photocatalytic activity than TiO2/SiO2 nanofiber mat, which does not contain carbon. The enhanced performance of the TSC NFM can be attributed to the improved adsorption capacity toward the organic pollutants due to the presence of carbon and to the enhanced interfacial charge separation between TiO2 nanoparticles and carbon. Besides, the as-prepared TSC NFM displays good stability and reusability. Notably, the flexible TSC NFM can be used in a continuous-flow reactor to efficiently treat wastewater. Our work provides new insights into the fabrication of carbon-based inorganic nanofiber mats, which have great potential in water treatment.

This work shows an easy and eco-friendly methodology to obtain almost pristine anatase phase of TiO2 by using furfural, a biomass-derived molecule, as a bio-template. The photocatalytic activity was studied following the degradation of methylene blue and phenol under artificial solar irradiation. Results were compared against those obtained on a commercial pristine anatase TiO2. The pseudo first-order, the second-order and the intraparticle diffusion kinetic models were verified. The textural and surface chemistry properties of the materials were correlated with the surface density of molecules adsorbed in equilibrium. The reaction-rate showed an almost perfect quadratic regression as a function of the surface density. Theoretical estimations of the density of states by DFT + U were performed showing that the total electron charge in the oxygen bonded to anatase TiO2 increased due to carbon doping in agreement with the prediction of appearance of atomic orbitals 2p from carbon atom in the hybrid material. C-doping is responsible of the red-shift from 3.14 to 2.94 eV observed for a Ti15O32C super-cell than pristine anatase Ti16O32. The increase in the activity of the C-doped TiO2 photocatalyst was due to the decrease in the energy band-gap promoting a higher absorption of photons from the visible light.

Different morphologies and crystal phases of black titanium dioxide (TiO2) were synthesized using Pulsed Laser Ablation in Liquid (PLAL). The synthesized laser modified black TiO2 (LMB-TiO2) structures included hydrogenated anatase TiO2 nanoparticles, as the core shell structures, and TiO2 microspheres. TiO2 core-shell nanoparticles, which had crystalline-disordered structures, demonstrated the laser ablation pulse duration-dependence growth of amorphous shells and hence formation of disordered TiO2 nanoparticles with different thickness of hydrogen-doped amorphous shells were shown. TiO2 microspheres with the yolk–shell like structures (YSHL-TiO2 microspheres), on the other hand, showed the formation of rutile phases in the shell which encapsulate Lattice Expanded Planes (LEPs) in the core. The microspheres demonstrated phase transitions from anatase to rutile and size-dependent lattice interlayers expansion from 0.35 nm to 0.94 nm. The maximum particle size growth occurred when the samples were subjected to the laser ablation for 120 min. The crystal phase transition, consequently, led to the formation of heterostructured photocatalysts through construction of hydrogenated anatase TiO2 nanoparticles junctions with rutile TiO2 microspheres. The photocatalytic degradation of methylene blue (MB) using LMB-TiO2 heterostructure was tested under visible light irradiation Results showed approximately 99% of MB was degraded after 60 min. Enhanced visible light absorption and increased charge carrier lifetime due to formation of different types of heterojunctions may explain the higher photocatalytic performance of LM-TiO2 samples. Moreover, the Photoluminescence analysis indicated that hydroxyl radicals were the main active species involved in the photocatalytic degradation tests and therefore the photocatalysis mechanism was accordingly suggested.

Hierarchical macro-mesoporous anatase TiO single crystal is one-pot synthesized in an EtOH-H O system using polystyrene (PS) as the single porogen both for macropore and mesopore and TiF as the titanium precursor. The key to the simultaneous growth of single crystal and the introduction of hierarchical pores is the assembly of PS and titania at the glassification temperature of PS (100 °C). During the hydrolytic polymerization of TiF , PS is encapsulated inside titania and gradually glassified. The interference from elastic PS on the oriental growth of TiO crystallite is thus minimized and the final removal of PS through calcination leaves interconnected macropore and mesopore inside the single crystal. According to XPS, EPR and fluorescence analyses, abundant oxygen vacancies are formed on the hierarchical porous single crystal, which presents extraordinary photocatalytic activity and stability in degrading organic pollutants under simulated sunlight irradiation using Rhodamine B as the model. The improved photocatalytic activity is a synergistic effect of improved separation of charge carrier and facilitated interfacial charge transfer benefitting from highly accessible porous single crystal structure. [Abstract copyright: Copyright © 2018 Elsevier Inc. All rights reserved.]

Photocatalytic activity of TiO2 nanoparticles is highly dependent on their phase composition. The coexistence of anatase and rutile phases in a single nanoparticle eases the electron transfer process between the phases, and favors the separation of photogenerated pairs. In this work, highly photoactive mixed-phase TiO2 nanostructures were prepared by supercritical antisolvent precipitation (SAS), an environmentally friendly technology. It is shown here that this methodology has the remarkable ability to produce highly porous (515 m2/g) and crystalline TiO2 nanoparticles. The phase composition of as-prepared TiO2 samples can be tailored through annealing process. Several mixed-phase TiO2 samples were tested to assess the correlation between photocatalytic activity and phase composition. The photocatalytic performance is strongly affected by the anatase-rutile ratio, since the synergism between phases enhances the charge separation, reducing the recombination effect of the photogenerated pairs (e−/h+). It was found that the nanocatalyst composed by 7.0 wt% of rutile phase and 93.0 wt% of anatase phase, named as TiO2_650, presented the highest photodegradation for both methyl orange (MO) and methylene blue (MB) dyes. Interestingly, TiO2 samples prepared by SAS have superior photoactivity than the benchmark photocatalyst names as P25, which is a widely used TiO2 material composed of anatase and rutile phases.

A polymer photocatalyst system was synthesized using a poly(styrene-block-acrylic acid) (PS-b-PAA) containing TiO2 gel without calcination, and its activity characteristics were assessed with methylene blue (MB) photodegradation test in water under visible light irradiation. The initial photodegradation activity was controllable by the polymer chain length and PAA/PS molar ratio. The longer polymer chain length provoked the activity decrease by macromolecular crowding effect. The lower molar ratio did an increase in the photocatalytic surface area by generation of a large number of anatase TiO2 crystal nuclei, leading to the activity increase. The copper phthalocyanine (CuPc) loading remarkably improved the activity. A higher active site was formed on the interface and showed good recycling performance.

Graphitic carbon nitride (CN) generally needs to be exfoliated into ultrathin nanosheets to reduce photocarrier recombination. However, the exfoliation of CN into nanosheets also reduces the light absorption. How to simultaneously realize low photocarrier recombination and high light absorption remains a challenge in the practical application of CN in photocatalysis. Herein, the light absorption of CN nanosheets was enhanced by introducing hollow TiO2 (h-TiO2) dielectric resonators. The h-TiO2/CN heterostructures were prepared by thermally polymerizing dicyandiamide in the presence of h-TiO2. The electromagnetic resonances of the h-TiO2 resonator creates strong electric field enhancement within, inside, and near external surface of the introduced h-TiO2 nanoshells. The enhanced electric field greatly improves the light absorption of CN located in these regions. The largest hydrogen evolution rate for h-TiO2/CN can reach 6.3 mmol g−1h−1, which is over 3-fold that of pure CN (2.0 mmol g−1h−1). It is also found that the small amount of CN within and inside h-TiO2 majorly contributes to the photocatalytic performance. These findings open a new avenue by which to enhance the performance of photocatalysts and will be helpful in the design of highly efficient photocatalysts for various reactions.

The efficient adsorption and activation of inert N2 molecules on a heterogeneous electrocatalyst surface are critical toward electrochemical N2 fixation. Inspired by the bimetallic sites in nitrogenase, herein, we developed a bi-metallic tin-titanium (Sn–Ti) structure in Sn-doped anatase TiO2 via an oxygen vacancy induced engineering approach. Density functional theory (DFT) calculations indicated that Sn atoms were introduced in the oxygen vacancy sites in anatase TiO2 (1 0 1) to form Sn–Ti bonds. These Sn–Ti bonds provided both strong σ-electron accepting and strong π-electron donating capabilities, thus serving as both N2 adsorption and catalytic N2 reduction sites. In 0.1 M KOH aqueous solution, the Sn-TiO2 electrocatalyst achieved a NH3 production rate of 10.5 μg h−1 cm−2 and a corresponding Faradaic efficiency (FENH3) of 8.36% at −0.45 V vs. reversible hydrogen electrode (RHE). Our work suggests the potential of atomic-scale designing and constructing bimetallic active sites for efficient electrocatalytic N2 fixation.

Flame retardant and visible light-activated Fe-doped TiO2 thin films were anchored to wood surfaces by a facile precipitation method for the photocatalytic degradation of gaseous formaldehyde. All of the as-prepared TiO2 thin films exhibited the anatase crystal structure and grew on the wood surfaces by the aggregation of nanoparticles with diameters ranging from 11 to 16 nm. The UV–vis diffuse reflectance spectroscopy (UV–vis DRS) results showed that the presence of a small amount of iron ions in the TiO2 matrix could significantly extend the optical responses in the UV to visible region. Compared to the pure TiO2/wood samples, the Fe-doped TiO2/wood samples exhibited higher photocatalytic activities under visible light irradiation. The optimum nFe/nTi molar ratio was 2.0 at. %. The electron spin resonance (ESR) tests further confirmed that the active oxygen species of OH and O2– that were generated on the Fe-doped TiO2/wood samples under visible light irradiation are responsible for the degradation of formaldehyde. The Fe-doped TiO2 samples also exhibited high stability and reusability after 6 cycles. Additionally, the limiting oxygen index of the original wood increased from 24.8% to 33.9% after it was coated with Fe-doped TiO2 thin films, indicating a significant improvement in its flame resistance.

Plasmon Ag decorated 3D urchinlike N-TiO2−x photocatalysts are successfully synthesized by a facile hydrothermal treatment (180 °C) and combined with a photo-deposition approach, followed by a reduction treatment. The results show that the resultant Ag/N-TiO2−x sample possesses a three-dimensional (3D) urchinlike nanostructure with high crystallinity of anatase. Meanwhile, it exhibits the narrow optical band gap (Eg ∼ 2.61 eV) and the excellent visible-light-driven photocatalytic performance. Moreover, the hydrogen generation rate and photocatalytic degradation rate of phenol are up to 186.2 μmol h−1 g−1 and 97.7% under visible light irradiation, which are about 4.2 and 5.4 folds greater than that of N-TiO2. The mechanism of photocatalytic process is also proposed, and the enhanced photocatalytic property is mainly due to the synergistic reaction of the Ti3+ and N codoping, which narrows the band gap and favors the utilization of visible light, and the plasmon effect of Ag nanoparticles and unique 3D urchinlike architecture, which are propitious to the separation and transmission of photogenerated carriers.

N-doped carbon coated TiO2 nanoparticles (TiO2@NC) were synthesized through a simple two-step route, in which dopamine was simultaneously utilized as both nitrogen and carbon sources. With TiO2@NC applied in the Na-ion battery (SIB) anodes, the continuous and uniform N-doped carbon layer can not only enhance the electrical conductivity of TiO2 and facilitate the surface pseudocapacitive process, but also serve as a buffer layer to accommodate the volume expansion during the sodiation-desodiation processes. The as-prepared TiO2@NC exhibits excellent electrochemical performance when utilized as the SIB anodes, which delivers a remarkably high reversible capacity of 250.2 mAh g-1 at a rate of 0.25C (84 mA g-1) after 200 cycles and still retains 122.1 mAh g-1 at 10C (3.35 A g-1) even after 3000 cycles accompanied with a 95.3% retention of the maximum capacity, outperforming most of the reported TiO2/C-based composites as SIB anodes. To our best knowledge, the preparation of TiO2@NC with dopamine as both nitrogen and carbon sources and its application in the SIB anodes are reported for the first time.

As a new carbon-based material, carbon dots (C-dots) have got widely preference because of its excellent electronic transfer capability. In this work, a novel ternary layered C-dots/g-C3N4/TiO2 nanosheets (CGT) composite photocatalysts were prepared by impregnation precipitation methods. The optimal ternary CGT composite samples revealed high photocatalytic hydrogen evolution rate in triethanolamine aqueous solutions, which exceeded the rate of the optimal g-C3N4/TiO2 composite sample by a factor of 5 times. The improved photocatalytic activity is owed to the positive effects of C-dots and layered heterojunction structure of TiO2 nanosheets and g-C3N4 sheets. C-dots in the CGT composites can serve as electron reservoirs to capture the photo-induced electrons. The well-defined layered heterojunction structure of CGT provides the intimate contact and the strong interaction of anatase TiO2 nanosheets and g-C3N4 sheets via face-to-face orientation, which restrains the recombination of photogenerated charge carriers, and thus enhances the photocatalytic H2-production activity. Electron paramagnetic resonance and transient photocurrent response proved the strong interaction and improved interfacial charge transfer of TiO2 nanosheets and g-C3N4 sheets, respectively. The mechanism of improving the photocatalytic H2-evolution activity was further confirmed by time-resolved fluorescence, electron paramagnetic resonance, transient photocurrent response and electrochemical impedance spectroscopy.

Titanium dioxide (TiO 2 ) has gained increasing interest in materials research due to its outstanding properties and promising applications in a wide range of fields. From this perspective, we report the synthesis of custom-designed anatase TiO 2 submicrometer particles coated with partial Au shells (ATiO 2 -AuShl). The synthetic strategy used herein yields uniformly shaped monodisperse particles. Amorphous TiO 2 core particles were synthesized using template-free oxidation and hydrolysis of titanium nitride (TiN); subsequent hydrothermal treatment generated anatase TiO 2 (ATiO 2 ) particles. Coating ATiO 2 particles with partial Au shells was accomplished using a simple seeded-growth method. Evaluation of the optical properties of these ATiO 2 -AuShl particles showed that these submicrometer composites exhibited an intense absorption peak for TiO 2 in the UV region (∼326 nm) and a broad extinction band in the visible range (∼650 nm) arising from the incomplete Au shell. These ATiO 2 -AuShl composite particles provide a unique and effective means for broadening the optical response of TiO 2 -based nano- and micron-scale materials. The simplicity of our synthetic method should broaden the application of ATiO 2 -AuShl particles in various visible light-driven technologies.

In this paper, a photocatalyst composed of TiO2 nanoparticles supported on the nanofibers of poly(methyl methacrylate) (PMMA) was successfully prepared by hydrothermally treating the electrospun PMMA nanofibers containing titanium n-butoxide precursor at 135°C for 8h. As-prepared composite was characterized by field-emission scanning electron microscopy, X-ray diffraction pattern, thermal gravimetric analysis and Brunauer-Emmett-Teller (BET) surface area measurements. It is revealed that high content (42%) of tetragonal anatase TiO2 nanoparticles are uniformly loaded on the PMMA nanofibers to constitute the composite (TiO2@PMMA) photocatalyst with BET surface area of 21.4m2g-1. The photocatalytic activity of TiO2@PMMA towards the degradation of methyl orange (MO), a model pollutant, has been investigated. It is observed that 0.1g of the composite could degrade 100mL of MO (10mg/L) completely within 50min under UV illumination, exhibiting a high catalytic activity. Moreover, the composite could be easily separated from the reaction system by filtration, and maintain high photocatalytic activity in five consecutive cycles of the degradation of MO, suggesting its potentials in recycling use. The work provides a new approach for the development of novel supported photocatalysts with high catalytic activity and good reusability.

Effective heterostructures for photocatalysis need to present good electron-hole mobility among phases, a feature that is only attained with satisfactory interface quality. For very small sizes and with a stable colloidal state, the oriented attachment mechanism can be used to prepare suitable structures by means of a building blocks strategy, whereby preformed nanoparticles are used to control the desired amount of each phase in the heterostructure. Here, we show the success of this strategy for anatase TiO2/rutile SnO2 heterostructures, applying conventional hydrothermal annealing, where successive collisions among particles increase the probability of oriented attachment. The photodegradation of Rhodamine B in water under UV radiation was used as a probe reaction to evaluate formation of the heterostructure, as indicated by an increase in photoactivity. Increased heterostructure photoactivity was related to heterojunction formation and charge separation. The increased lifetimes of the photogenerated charges, due to heterojunction formation, enabled them to reach the oxides surface and promote photocatalytic reactions. The insights presented here may be used in a rationalized synthesis method to obtain heterostructures from preformed nanocrystals.

Ti3+ self-doped mesoporous black TiO2/graphene assemblies are fabricated by a facile solvothermal method and surface hydrogenation. The structure, crystallinity, morphology, and chemical state of the as-prepared samples are characterized in detail by X-ray diffraction, Raman, X-ray photoelectron spectroscopy, transmission electron microscopy, N2 adsorption and UV-visible diffuse reflectance spectroscopy. The results show that the presence of Ti3+ can efficiently extend the photoresponse of anatase TiO2 to visible light region. The solar-driven photocatalytic hydrogen evolution shows that Ti3+ self-doped mesoporous black TiO2/graphene assemblies exhibit the highest photocatalytic activity (186μmolh-1 0.01g-1), exceeding to mesoporous TiO2/graphene assemblies and mesoporous black TiO2. It also exhibits superior photoelectrochemical properties compared with mesoporous TiO2/graphene assemblies. The unpredicted-high photocatalytic performance is attributed to the close contact between the unique two-dimensional graphene structures coupled with TiO2 mesoporous architectures resulting in outstanding charge separation efficient and the Ti3+ self-doping extending the utilization ratio of visible light.

The photoexcited electrons transfer dynamics at the TiO2 film/fluorine doped tin oxide (FTO) interface of anatase TiO2 nanowire arrays (NWAs) and QD-sensitized TiO2 NWAs films have been studied by using surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Various SPV and TPV responses were obtained when the laser beam was incident from the front side illumination and back side illumination. Based on the work function values of anatase TiO2 NWAs and FTO, the results indicate that diffusion is the major way for the separation and transfer of the photoexcited charge in the both anatase TiO2 NWAs and QD-sensitized TiO2 NWAs films under front side illumination. And the photoexcited charge were separated by drift under the built-in electric field at the TiO2 film/FTO interface for anatase TiO2 NWAs and QD-sensitized TiO2 NWAs films under back side illumination. In addition, under back side illumination the built-in electric field and band structure of CdS/CdSe QDs and anatase TiO2 NWAs lead to the separation and transfer of the photoexcited charge for CdS/CdSe QDs sensitized TiO2 NWAs/FTO film. As the intensity of illumination increases, the effect of built-in electric field on the separation and transfer of the photoexcited charge in the QD-sensitized TiO2 NWAs film decreases.

Virus inactivation by nanoparticles (NPs) is hypothesized to affect virus fate and transport in the subsurface. This study examines the interactions of viruses with titanium dioxide (TiO2) anatase NPs, which is a good disinfectant with unique physiochemical properties. The bacteriophage MS2 was used as a model virus. A series of batch experiments of MS2 inactivation by TiO2 NPs were conducted at room temperature (25°C), in the presence and absence of quartz sand, with and without ambient light. Three sets of experiments were performed in phosphate buffered saline solution (PBS) and one in distilled deionized water (ddH2O). The virus inactivation experimental data were satisfactorily fitted with a pseudo-first order expression with a time dependent rate coefficient. Quartz sand was shown to affect MS2 inactivation by TiO2 NPs both in the presence and absence of ambient light, because, under the experimental conditions of this study, the quartz sand offers a protection to the attached MS2 against inactivation. Moreover, it was shown that low TiO2 concentration (10mg/L) affected only slightly MS2 inactivation with and without ambient light. Furthermore, PBS hindered MS2 inactivation by TiO2 NPs.

Anatase TiO 2 crystal facets are garnering increasing attention due to their unique surface property. However, no specific linear relationship had been derived between the facet exposed on TiO 2 and the surface adsorption capacity as well as photocatalytic performance. This study systematically explored the facet effects on antimony (Sb) adsorption and photocatalytic oxidation using high-index {201} and low-index {101}, {001}, and {100} TiO 2 . The results suggest that high-index {201} TiO 2 exhibits the best Sb(III) adsorption and photocatalytic activity compared to the low-index TiO 2 . Both the Sb(III) adsorption density and the amount of OH and O 2 − generated in solution were correlated to the magnitude of surface energy on TiO 2 facets. Photocatalytically generated OH and O 2 − were responsible for Sb(III) photooxidation as evidenced by radical-trapping experiments. The great contribution of OH was observed only on {201}, not on low-index TiO 2 . This phenomenon was found to be attributable to the high surface energy on {201}, which enables the generation of a large amount of photogeneration OH to compensate for the fast rate of OH dissipation. Therefore, the predominant participation of OH in Sb(III) photooxidation was only possible on high-index {201} TiO 2 , which resulted in an enhanced photocatalytic rate. On the other hand, O 2 − dominated the Sb(III) photocatalytic oxidation on low-index TiO 2 . The intrinsic facet-dependent adsorption and photocatalytic mechanism obtained from this study would be useful for developing TiO 2 -based environmental technologies.

Crystal facet engineering and surface modification of semiconductor have become important strategies to improve photocatalytic activity by optimizing surface charge carrier separation/transfer and extending solar spectrum utilization. In this work, we report anatase single-crystalline TiO 2 hollow tetragonal nanocones with large exposed (1 0 1) facets by a facile liquid-phase interfacial synthetic strategy, using the hydrolysis of tetrabutyltitanate with adscititious water in the organic solvent of cyclohexane and a capping agent of 1, 6-hexanediamine. The specific surface area of these TiO 2 hollow tetragonal nanocones is as high as 331.3 m 2 /g. Thanks to large exposed (1 0 1) facets and high surface area, these TiO 2 hollow tetragonal nanocones exhibited excellent full-arc photocatalytic activities for the degradation of organic pollutants. Remarkably, the butoxy group could be modified onto TiO 2 hollow tetragonal nanocones through post-synthesis treatment in tetrabutyltitanate glycol solution, which brought about eximious visible light photocatalytic activities for the degradation of colored dyes of RhB and MO, especially for RhB, by virtue of much improved electron trapping ability of the Ti-O group from the excited dye due to the strong electronegativity of the oxygen atom in the butoxy group. This work advances us to rationally tailor the atomic and electronic structure of the photocatalyst for outstanding photocatalytic properties in various environmental and energy-related applications.

On the basis of measurements, such as field emission scanning electron microscope, UV-Vis diffuse reflectance spectra, X-ray diffraction, electron paramagnetic resonance, photoluminescence spectra, and photocurrent measurements, the roles of anatase TiO2 sheet on synthesizing Ti3+ self-doped mixed phase TiO2 nanosheets (doped TiO2 (A/R, TiO2 (A))) and on improving the performance for photocatalytic CO2 reduction were explored systematically. High surface area anatase TiO2 nanosheets (TiO2 (A)) as a substrate, structure directing agent, and inhibitor, mediated the synthesis of Ti3+ self-doped mixed phase TiO2 nanosheets. Addition of TiO2 (A) significantly improved not only visible light absorption of doped TiO2 (A/R, TiO2 (A)), but also the efficiency of photo-excited charges separations due to the existence of interfacial regions of anatase-rutile TiO2 junctions. Finally, a possible mechanism for interfacial charge transfer at the anatase-rutile TiO2 interface and for photocatalytic CO2 reduction over Pt loaded doped TiO2 (A/R, TiO2 (A)) were proposed.

Chemical doping is a widely-used strategy to improve the performance of TiO 2 for the dye-sensitized solar cells (DSCs). However, the effect of two efficient dopants has been rarely investigated. We present the synthesis of GO@SnO 2 /TiO 2 nanofibers (NFs) by a facile method using electrospinning and hydrothermal processes. The synthesized NFs are described in terms of morphology, crystallinity and chemistry through FESEM, TEM, HR-TEM, XRD, EDX, XPS, FT-IR and Raman spectra. As the results, the axial ratio and the average diameter of NFs decreased after the hydrothermal treatment and calcination process, respectively. The prepared Titania-based nanofibers have 81.82% anatase and 18.18% rutile-structure. The developed materials are applied as working electrodes of DSCs. The photovoltaic performances showed that the efficiency of the device employed GO@SnO 2 /TiO 2 photoanode gave 5.41%, which was higher than those of cells fabricated with SnO 2 /TiO 2 NFs (3.41%) and GO@TiO 2 NFs (4.52%) photoanodes. The photovoltaic parameters such as J sc , V oc , FF and R ct are calculated and found to be 11.19 mA cm −2 , 0.72 V, 0.67 and 9.26 Ω, respectively. The high photovoltaic response of DSC based of GO@SnO 2 /TiO 2 NFs may be attributed to the large surface area of the NFs, and the low electron recombination. Furthermore, the start-stop switches of the cell devices with the developed photoanode affirmed the stability and photovoltaic performance of the cell.

Amphiphilic catalysts composed of carbon nanotubes (CNTs) and titanate nanotubes (TiNTs) have been successfully synthesized by refluxing anatase TiO2 and functionalised CNTs in concentrated NaOH solution. The prepared materials were characterized by transmission electron microscopy, scanning electron microscopy, X-ray diffraction, thermogravimetric analysis (TGA), and N2 physisorption isotherms. The catalytic activity of the synthesized composites was first evaluated in the oxidation of methyl yellow (MY) using H2O2 as oxidant in a single liquid phase system and in a biphasic water/oil mixture. The results of these experiments indicated that the catalytic activities of nanocomposites were very similar in the single liquid-phase oxidation. However, the modification of TiNTs with CNTs led to a substantially enhanced MY oxidation in the biphasic system. The nanocomposites show excellent interaction with both hydrophilic and hydrophobic compounds and thus stabilise emulsions. Under biphasic conditions, the catalysts can be easily separated and recycled, retaining catalytic activity even after eight runs. Additionally, the hybrid materials show superior catalytic activity and selectivity in the biphasic oxidation of benzyl alcohol with H2O2, as compared to pure TiNTs.

Nanocavities are empty voids exposed on the surface of one dimensional TiO2 nanostructured material. Often, they exhibited beneficial optical and electrical properties that leads to efficient photocatalytic reactions. This study reports formation of nanocavities on anatase TiO2 nanobelts (TNB) through dehydroxylation of surface hydroxyl groups during calcination process (350–600 °C). The morphological and crystal structure analysis of TNB-500, -550 and -600 displayed the nanobelts shape with high density of nano-size cavities and increase in average diameter with calcination temperature. The SAED patterns confirm the anatase TiO2 phase. The enhanced light absorption properties of biphasic anatase/TiO2-B and anatase TiO2 than H2Ti3O7 are attributed to transformation of crystal structure upon calcination process. The catalytic activity was evaluated for degradation of methyl orange dye in aqueous solution under solar light irradiation. The reaction variables such as calcination temperature, amount of catalyst and pH of the methyl orange dye solution were studied and discussed in detail. Under optimal experimental conditions TNB-550 photocatalyst displayed highest degradation performance about 8 folds higher than H2Ti3O7. The high performance is explained as due to synergistic properties of one dimensional anatase TiO2 with high density of nanocavities leading to one dimensional transfer of electrons and high absorption co-efficient in UV-A spectrum are suitable for efficient red-ox reactions.

We report a C-doped mesoporous anatase TiO2 with high surface area synthesized using multi-walled carbon nanotube (MWCNT) mat as a "rigid" template and carbon doping source. The characterization by SEM, HRTEM, X-ray diffraction and nitrogen adsorption revealed that TiO2 samples have a porous structure which are figuratively a inverse copy of MWCNT network and pore walls are formed by interconnected TiO2 nanoparticles with average diameter of ∼10nm. We found that annealing temperatures from 400 to 1000°C before MWCNT template removal had very limited effect on particle size (∼10nm), surface area (112-129m(2)/g) and total pore volume (0.74-0.85m(2)/g) of the samples through a significantly delayed phase transition from anatase to rutile started at 800°C, resulting in only ∼9.1% conversion at 1000°C. The pore size distribution is in mesopore range from 6 to 60nm peaked at ∼24nm. XPS analysis showed a relatively strong C1s peak at 288.4eV, indicating C doping at Ti sites, which is responsible for red shift of adsorption edge of UV-vis spectra and photocatalytic activity in visible-light region.

An effective way to modify the photocatalytic activity of both anatase and rutile TiO2 nanoparticles by coating the surface with either an inorganic (SiO2/silica) or organic (green-tea) layer using a chemical approach is demonstrated. Tetraethyl orthosilicate (TEOS) was used to cover the surface of TiO2 with silica which facilitates the inhibition of photocatalytic activity, ensuring its application in sunscreens by blocking the reactive oxygen species (ROS). Green-tea extract, rich in epigallocatechin gallate (EGCG), was used to coat/stabilize nano-sized TiO2. The morphology of these coatings was revealed by transmission electron microscopy (TEM) and by energy dispersive spectroscopy (EDS) mapping. These studies showed good coverage for both types of coating, but with somewhat better uniformity of the coating layer on rutile TiO2 compared to anatase due to its more uniform particle geometry. The effectiveness of each coating was evaluated by photodegradation of an organic dye (methyl orange). These studies showed rutile_polyphenol exhibits the highest photocatalytic activity among rutile forms which validates its feasibility to be used in photodegradation.

Brookite titanium dioxide (TiO2) is rarely studied, as compared with anatase and rutile phases TiO2, due to its comparatively lower photoactivity. It has been recently reported that brookite TiO2 with active facets exhibits excellent performance, however, synthesis of such faceted brookite TiO2 is difficult because of its low thermodynamic phase stability and low structural symmetric. Furthermore, like faceted anatase and rutile TiO2, faceted brookite TiO2 is not responsive to visible light due to its wide bandgap. In this study, a novel dopant, hydrazine, was introduced in the development of nitrogen doping. By applying this dopant, nitrogen doped brookite nanorods with active {120}, {111} and {011¯} facets were successfully synthesized. The resultant materials exhibited remarkably enhanced visible-light photoactivity in photodegradation.

The surface of oleic acid stabilized rod-shape anatase TiO2 nanocrystals was modified by adsorption of Eu(3+) ions. The Eu(3+) attachment showed Langmuir adsorption behavior, thus the loading of Eu(3+) could be controlled precisely up to surface saturation coverage. The Eu(3+)-TiO2 nanorods show weak Eu(3+) based luminescence. However, addition of thenoyltrifluoroacetone (TTFA) leads to coordination of the ligand to the Eu(3+) centers and the TTFA-Eu(3+)-TiO2 materials exhibit strong Eu(3+) fluorescence sensitized by the TTFA ligand.

Identification of the role of the specific surface area and surface structure as a key factor for photocatalytic performance remains a controversial topic. In this work, three types of N-doped anatase TiO2 with different morphologies are newly synthesized by changing the addition order for the reagents. Methyl orange, Rhodamine B and Congo red are selected to showcase the photoactivity of the synthesized N-doped TiO2. The photocatalytic experimental results show that Congo red can be selectively and rapidly degraded by three different N-doped TiO2 samples. Interestingly, although a microspiny sphere structure possesses a larger specific surface area compared to a microflower structure, a microflower structure dominated by {1 0 0} and {1 0 1} facets exhibits a higher photocatalytic efficiency compared to a microspiny structure dominated by {1 0 1} facets, as demonstrated by a quicker photodegradation rate for Congo red, higher photocurrent density, smaller semicircle in the electrochemical impedance spectrum, and lower photoluminescence intensity. Thus, the result suggests that the surface structure plays a more important role compared to the surface area. In addition, a hollow microsphere structure with the largest specific surface area exhibits the best performance in terms of photodegradation, charge separation ability and electron-hole recombination efficiency, indicating that the proper surface morphology combined with a large specific surface area is greatly promising for enhancement of photoactivity.

Palygorskite (Pal) is a kind of low-cost and environment-friendly natural nanoclay material with tubular structure and excellent hydrophilicity. TiO2 nanoparticles, especially anatase phase, have prominent photocatalytic bactericidal and organic pollutant decomposition activities. In this work, Pal and Pal/TiO2 nanocomposite were successfully embedded in the polyamide (PA) selective layer of the reverse osmosis (RO) membranes via interfacial polymerization. The tubular structure of Pal possesses a cross-sectional area of 0.37 × 0.63 nm2, which facilitates the selective transport of water molecules through PA layers. The water flux of Pal incorporated TFN membrane increases to approximately 40 l·m−2·h−1 at 16 bar, which is 1.6-fold higher than the reference TFC membrane. Meanwhile, the NaCl rejection is maintained at approximately 98%. Although the Pal/TiO2 incorporated TFN membrane exhibited slightly lower flux (1.4-fold higher than TFC), the embedded Pal/TiO2 contributed to the antifouling and photocatalytic bactericidal capacities and the salt rejection maintained at an acceptable level of 98%, which are greatly desired in the membrane desalination and water reclamation processes.

In this work, representative semiconductors CdS, V2O5, WO3 and P25 (Degussa TiO2 consisting of 80 wt% anatase and 20 wt% rutile) were chosen as the photocatalysts, and the common phenol along with its derivatives (p-nitrophenol, p-chlorophenol and hydroquinone) were designated as the probe pollutants. The energy levels of the frontier molecular orbitals (EHOMO and ELUMO) of organics, and the valence band (VB) and conduction band (CB) energy levels (EVB and ECB) of photocatalysts were obtained through experiments and calculations. By correlating the photocatalytic activities of photocatalysts for the degradations of the organic pollutants under the irradiation of a 300 W xenon lamp with their above-mentioned energy levels, some new findings can be acquired. To be specific, the more positive EHOMO of an organic pollutant leads to its easier photodegradation by photocatalysts. Meanwhile, the more negative VB position for a photocatalyst results in the higher photocatalytic activities for the degradations of organic pollutants. Therefore, the matching correlation between the EHOMO of an organic pollutant and the EVB of a photocatalyst is of great importance to the efficiency of photocatalytic degradation.