Mesoporous TiO2: Preparation, Doping, and as a Composite for Photocatalysis

Influence of Co3O4 Nanostructure Morphology on the Catalytic Degradation of p-Nitrophenol

The design and fabrication of nanomaterials with controllable morphology and size is of critical importance to achieve excellent catalytic performance in heterogeneous catalysis. In this work, cobalt oxide (Co3O4) nanostructures with different morphologies (nanoplates, microflowers, nanorods and nanocubes) were successfully constructed in order to establish the morphology-property-performance relationship of the catalysts. The morphology and structure of the nanostructured Co3O4 were characterized by various techniques, and the catalytic performance of the as-prepared nanostructures was studied by monitoring the reduction of p-nitrophenol to p-aminophenol in the presence of excess NaBH4. The catalytic performance was found to be strongly dependent on their morphologies. The experimental results show that the pseudo-first-order reaction rate constants for Co3O4 nanostructures with various shapes are, respectively, 1.49 min-1 (nanoplates), 1.40 min-1 (microflowers), 0.78 min-1 (nanorods) and 0.23 min-1 (nanocubes). The Co3O4 nanoplates exhibited the highest catalytic activity among the four nanostructures, due to their largest specific surface area, relatively high total pore volume, best redox properties and abundance of defect sites. The established correlation between morphology, property and catalytic performance in this work will offer valuable insight into the design and application of nanostructured Co3O4 as a potential non-noble metal catalyst for p-nitrophenol reduction.

Cu-doped mesoporous TiO2 photocatalyst for efficient degradation of organic dye via visible light photocatalysis

A solvothermal method was used to synthesize the mesoporous TiO2, (1-3w %) Cu-doped mesoporous TiO2 membrane with the help of a bioreactor. To understand the physicochemical composition of all synthesized nanomaterials, the structure, morphology and crystallinity of the materials were studied using X-ray diffractometer (XRD), Field emission scanning electron microscopy (FESEM), Fourier transform-infrared (FTIR), Energy dispersive X-ray spectroscopy (EDS) and cyclic voltammetry (CV). Under artificial light source (500 W mercury bulb) irradiations, the nano catalysts' catalytic effectiveness was examined for the azo dyes, namely Congo red. Cu-doping causes a shift in the light absorption of mTiO2 from the ultraviolet to the visible region. The 3w% Cu-doped mTiO2 photocatalyst exhibits lower band gap energy (2.6eV) than TiO2 which is 3.2 eV to efficiently utilize solar energy. As a result, the light absorption was shifted towards the visible spectrum. The recommended mTiO2 and (1, 2, 3) w% Cu-doped mTiO2 photocatalysts were used to photodegrade Congo red and methylene blue. For the degradation of CR, the mTiO2 photocatalyst exhibited 61% and 3w% Cu-doped mTiO2 demonstrated 99% photocatalytic performance after 50 min. A variety of scavengers were also utilized to distinguish the active species by catching the radicals and holes created during the process of photocatalytic degradation. CV indicates the presence of Cu2+ and Cu1+ in Cu-doped mTiO2. Oxygen vacancies and the electronegative surface of Cu1+ seem to perform the photocatalytic reduction of CR.

S-Scheme 2D/2D Heterojunction of ZnTiO3 Nanosheets/Bi2WO6 Nanosheets with Enhanced Photoelectrocatalytic Activity for Phenol Wastewater under Visible Light

The pollution of phenol wastewater is becoming worse. In this paper, a 2D/2D nanosheet-like ZnTiO₃/Bi₂WO₆ S-Scheme heterojunction was synthesized for the first time through a two-step calcination method and a hydrothermal method. In order to improve the separation efficiency of photogenerated carriers, the S-Scheme heterojunction charge-transfer path was designed and constructed, the photoelectrocatalytic effect of the applied electric field was utilized, and the photoelectric coupling catalytic degradation performance was greatly enhanced. When the applied voltage was +0.5 V, the ZnTiO₃/Bi₂WO₆ molar ratio of 1.5:1 had highest degradation rate under visible light: the degradation rate was 93%, and the kinetic rate was 3.6 times higher than that of pure Bi₂WO₆. Moreover, the stability of the composite photoelectrocatalyst was excellent: the photoelectrocatalytic degradation rate of the photoelectrocatalyst remained above 90% after five cycles. In addition, through electrochemical analysis, XRD, XPS, TEM, radical trapping experiments, and valence band spectroscopy, we found that the S-scheme heterojunction was constructed between the two semiconductors, which effectively retained the redox ability of the two semiconductors. This provides new insights for the construction of a two-component direct S-scheme heterojunction as well as a feasible new solution for the treatment of phenol wastewater pollution.

Green Fabrication of Heterostructured CoTiO3/TiO2 Nanocatalysts for Efficient Photocatalytic Degradation of Cinnamic Acid

In this work, CoTiO₃/TiO₂ (CTO/Ti) heterostructures were prepared by a hydrothermal procedure in a neutral medium using perovskite CoTiO₃ and tetraisopropyl titanate. Characteristics of the synthesized catalysts were analyzed by various techniques including X-ray diffraction, Fourier transform infrared spectroscopy, Raman spectroscopy, UV-vis diffuse reflectance spectroscopy, Brunauer-Emmett-Teller adsorption-desorption, energy-dispersive X-ray spectroscopy, field emission scanning electron microscopy, high-resolution transmission electron microscopy, and point of zero charges. The activity in the photodegradation of cinnamic acid (CA) under UV-A irradiation of the CTO/Ti heterostructure was investigated and compared with individual materials TiO₂ (Ti-w) and CoTiO₃ (CTO). The investigation showed that the heterostructured CoTiO₃/TiO₂ catalyst with optimal composition (5% CTO) exhibited much higher photocatalytic activity for degradation of cinnamic acid than individual CoTiO₃ and TiO₂. Under the optimal conditions (C _cat = 0.75 g/L, Q _air = 0.3 L/min, and pH = 3.8) the 90 min conversion of cinnamic acid reached 80.9% on 5CTO/Ti, much higher than those of CTO (4.6%) and Ti-w (75.2%). It was found that the enhancement in activity for the CA removal of the CTO/Ti heterostructure was due to the construction of a heterojunction structure between TiO₂(Ti-w) and CoTiO₃ that resulted in an increase in the specific surface area and porosity, reduction of the band gap energy, and higher efficient separation of charge carriers on the surface to prevent recombination. Alternatively, a comparison of the recyclability of 5CTO/Ti and Ti-w was made for CA degradation. The results showed a decrease in the CA conversion by 38% on 5CTO/Ti and 48% on Ti-w after six reaction cycles.

Au nanoparticle-decorated TiO2 hollow fibers with enhanced visible-light photocatalytic activity toward dye degradation

TiO2 hollow fibers (THF) were prepared by a template method using kapok as a biotemplate and subsequently decorated by plasmonic Au nanoparticles using a solution plasma process. The THF exhibited an anatase phase and a hollow structure with a mesoporous wall. Au nanoparticles with a diameter of about 5-10 nm were uniformly distributed on the THF surface. Au nanoparticles-decorated TiO2 hollow fibers (Au/THF) have enhanced photocatalytic activity toward methylene blue degradation under visible light-emitting diode (Vis-LED) as compared to pristine THF and P25. This could be attributed to combined effects including effective light-harvesting by a hollow structure, large surface area due to a mesoporous wall of THF, and visible-light absorption and efficient charge separation induced by Au nanoparticles. The Au/THF also showed good recyclability and separation ability.

The role of seashell wastes in TiO2/Seashell composites: Photocatalytic degradation of methylene blue dye under sunlight

This paper proposes a sustainable and facile approach for the synthesis of photocatalysts in which shell waste is used as support material. The synthesized photocatalysts exhibited a significant performance in the mineralization of organic substances under solar irradiation or artificial lighting. Calcined abalone shell with a TiO₂ loading of 23.4% led to a significant improvement in optical absorption: the degradation efficiencies of methylene blue (MB) after 140 min under UV light, vis light, UV-vis light, and natural sunlight were 93%, 96%, 100%, and 100%, respectively. Notably, the byproducts obtained after the degradation by commercial P25 TiO₂ disappeared with the utilization of shell waste as support material. The Na, Sr, S present in the calcined abalone shell were doped into the substitutional sites of TiO₂ and were indispensable to achieve the desired band-gap narrowing and photocatalytic performance; moreover, the Ti and Zn oxides in the calcined abalone shell acted as semiconductors and improved the charge separation efficiency of TiO₂. Above all, this paper describes a green synthesis based on the use of waste seashell. This material acts as an excellent photocatalyst support for environmental pollution treatments, leading to the 'control of waste by waste' and opening up new possibilities for shell waste reutilization and sustainable chemistry.

Cobalt-bridged secondary building units in a titanium metal-organic framework catalyze cascade reduction of N-heteroarenes

We report here a novel Ti3-BPDC metal-organic framework (MOF) constructed from biphenyl-4,4'-dicarboxylate (BPDC) linkers and Ti3(OH)2 secondary building units (SBUs) with permanent porosity and large 1D channels. Ti-OH groups from neighboring SBUs point toward each other with an O-O distance of 2 Å, and upon deprotonation, act as the first bidentate SBU-based ligands to support CoII-hydride species for effective cascade reduction of N-heteroarenes (such as pyridines and quinolines) via sequential dearomative hydroboration and hydrogenation, affording piperidine and 1,2,3,4-tetrahydroquinoline derivatives with excellent activity (turnover number ∼ 1980) and chemoselectivity.

Titanium Dioxide (TiO2) Mesocrystals: Synthesis, Growth Mechanisms and Photocatalytic Properties

Hierarchical TiO2 superstructures with desired architectures and intriguing physico-chemical properties are considered to be one of the most promising candidates for solving the serious issues related to global energy exhaustion as well as environmental deterioration via the well-known photocatalytic process. In particular, TiO2 mesocrystals, which are built from TiO2 nanocrystal building blocks in the same crystallographical orientation, have attracted intensive research interest in the area of photocatalysis owing to their distinctive structural properties such as high crystallinity, high specific surface area, and single-crystal-like nature. The deeper understanding of TiO2 mesocrystals-based photocatalysis is beneficial for developing new types of photocatalytic materials with multiple functionalities. In this paper, a comprehensive review of the recent advances toward fabricating and modifying TiO2 mesocrystals is provided, with special focus on the underlying mesocrystallization mechanism and controlling rules. The potential applications of as-synthesized TiO2 mesocrystals in photocatalysis are then discussed to shed light on the structure–performance relationships, thus guiding the development of highly efficient TiO2 mesocrystal-based photocatalysts for certain applications. Finally, the prospects of future research on TiO2 mesocrystals in photocatalysis are briefly highlighted.

TiO2 Films Functionalized with ABDA for Enhanced Photoelectrochemical Performance

Efficient photogenerated charge separation is needed for potential solar energy conversion and storage. Herein, we present the preparation and characterization of an optically active anthracence-based molecule 4,4′-(anthracene-2,6-diylbis(azanediyl))bis(4-oxobutanoic acid) (ABDA), whose coupling with TiO2 has been proven useful in the pursuit of enhanced photoelectrochemical (PEC) performance. Ultraviolet-visible absorption spectroscopy and PEC measurements indicated that the ABDA/TiO2 composite has extended the light absorption of TiO2 to the visible region and efficiently increased the charge separation. The photocurrent of ABDA/TiO2 is 1.8 times higher than that of pristine TiO2. This study has provided a method for the development of functionalized TiO2 with enhanced PEC behaviour for energy conversion applications.

Mesoporous Titanium Dioxide: Synthesis and Applications in Photocatalysis, Energy and Biology

Mesoporous materials are materials with high surface area and intrinsic porosity, and therefore have attracted great research interest due to these unique structures. Mesoporous titanium dioxide (TiO₂) is one of the most widely studied mesoporous materials given its special characters and enormous applications. In this article, we highlight the significant work on mesoporous TiO₂ including syntheses and applications, particularly in the field of photocatalysis, energy and biology. Different synthesis methods of mesoporous TiO₂-including sol⁻gel, hydrothermal, solvothermal method, and other template methods-are covered and compared. The applications in photocatalysis, new energy batteries and in biological fields are demonstrated. New research directions and significant challenges of mesoporous TiO₂ are also discussed.

Defective Anatase TiO2-x Mesocrystal Growth In Situ on g-C3 N4 Nanosheets: Construction of 3D/2D Z-Scheme Heterostructures for Highly Efficient Visible-Light Photocatalysis

Environmental remediation by employing visible-light-active semiconductor heterostructures provides effective solutions for handling emerging contaminants by a much greener and lower cost approach compared with other methods. This report demonstrates that the in situ growth of nanosized single-crystal-like defective anatase TiO_2-x mesocrystals (DTMCs) on g-C₃ N₄ nanosheets (NSs) can produce a 3D/2D DTMC/g-C₃ N₄ NS heterostructure with the two components held together by chemical bonds to form tight interfaces. This nanostructured heterostructure displayed remarkably improved photocatalytic activity toward the removal of the model pollutants Methyl Orange (MO) and Cr^VI under visible-light irradiation in comparison with the pristine DTMC and g-C₃ N₄ NS components, which suggests that both the oxidation and reduction abilities of the DTMC/g-C₃ N₄ NSs were simultaneously enhanced after fabrication. On the basis of the results of a systematic characterization, a reasonable mechanism for the photocatalytic activity based on a direct Z-scheme heterojunction is proposed and further verified by the measurement of ^. OH. This novel Z-scheme heterojunction endows the heterostructure with improved photogenerated electron/hole pair separation and a strong redox ability for the efficient degradation of wastewater pollutants. This work will be useful for the design and fabrication of direct Z-scheme heterostructured photocatalysts with novel architectures for applications in energy conversion and environmental remediation.

Anthracene-decorated TiO2 thin films with the enhanced photoelectrochemical performance

New insight of introducing new organic compounds for the efficient photogenerated charge separation is vitally important for the current solar energy conversion. Herein, (2Z,2'Z)-4,4'-(anthracene-2,6-diylbis(azanediyl))bis(4-oxobut-2-enoic acid) (ADA)/TiO₂ composite thin film is fabricated through the wet-impregnation strategy, which exhibits excellent photoelectrochemical performance (PEC). A combined study of ultraviolet-visible absorption spectra, scanning Kelvin probe maps, electrochemical and photoelectrochemical measurements reveals that the ADA/TiO₂ composite with narrow bandgap of 2.42 eV extends the photo response to the visible light region. The photocurrent generated by the optimal ADA/TiO₂ is 2.5 times higher than that of the pristine TiO₂. The result is attributed to the broader light absorption range and the separation of photoelectrons and holes prompted by ADA. Moreover, the high stability of the ADA/TiO₂ composite favors the practical application. The present work may offer a promising strategy for the low-cost PEC cell in the clean solar hydrogen production.

Visible-Light-Activated Black Organotitanias: How Synthetic Conditions Influence Their Structure and Photocatalytic Activity

A series of low-temperature, visible-light-activated black organotitanias were synthesised through a sol-gel strategy that allowed the in situ incorporation of p-phenylenediamine (PPD) into the framework of anatase nanoparticles. The effect of the synthetic conditions on the crystalline structure and photocatalytic activity of these materials was assessed by several characterisation techniques, which revealed a small crystalline domain size (4.6-5.5 nm), effective incorporation of PPD inside the nanoparticles, and a significant reduction in the band gap of these materials (from 3.2 to 2.7-2.9 eV). A systematic study of the synthetic parameters also allowed a significant reduction of the solvent used for the preparation of these black organotitanias (20-fold), as well as the crystallisation time, without compromising the structural properties and photocatalytic activity of these materials. The organotitanias with the highest PPD content and high crystallinity result in the best performing materials in the photocatalytic degradation of rhodamine 6G under both UV- and visible-light irradiation.

Visible-Light-Controlled Oxidation of Glucose using Titania-Supported Silver Photocatalysts

The visible-light-mediated photo-catalytic selective valorisation of glucose using TiO2-supported Ag nanoparticles is shown for the first time. The optimisation of the catalyst composition, substrate-to-catalyst ratio and reaction medium proved that a near total suppression of the mineralisation pathway could be achieved with a selectivity to partial oxidation products and small-chain monosaccharides as high as 98 %. The primary products were determined to be gluconic acid, arabinose, erythrose, glyceraldehyde and formic acid. Under UVA light, the selectivity to organics decreases because of the production of CO2 from mineralisation. A reaction mechanism is proposed based on an α-scission process combined with the Ruff degradation reaction, which explains the presence of the oxidation products, the smaller carbohydrates and formic acid. X-ray photoelectron spectroscopy, UV/Vis spectroscopy and microscopy studies showed the presence of plasmonic 4 nm particles of silver that were oxidised to silver oxide over the course of the reaction, and recycling studies revealed that this was not detrimental to activity.

Black N/H-TiO2 Nanoplates with a Flower-Like Hierarchical Architecture for Photocatalytic Hydrogen Evolution

A facile two-step strategy was used to prepare black of hydrogenated/nitrogen-doped TiO₂ nanoplates (NHTA) with a flower-like hierarchical architecture. In situ nitriding and self-assembly was realized by hydrothermal synthesis using tripolycyanamide as a N source and as a structure-directing agent. After thorough characterization, it was found that the hydrogenation treatment did not damage the flower-like architecture but distorted the anatase crystal structure and significantly changed the band structure of NHTA owing to the increased concentration of oxygen vacancies, hydroxyl groups, and Ti³⁺ cations. Under AM 1.5 illumination, the photocatalytic H₂ evolution rate on the black NHTA was approximately 1500 μmol g^-1  h^-1 , which was much better than the N-doped TiO₂ nanoplates (≈690 μmol g^-1  h^-1 ). This improvement in the hydrogen evolution rate was attributed to a reduced bandgap, enhanced separation of the photogenerated charge carriers, and an increase in the surface-active sites.

Synthesis of hierarchically porous structured CaCO3 and TiO2 replicas by sol-gel method using lotus root as template

Intensive attention has been put in mimicking the morphologies in nature owing to their uniqueness, complexity, and diversity. One of the effective approaches to mimic bio-morphologies is through biotemplating - the technique of using biological structures as template to reproduce intricate structure in other forms of materials. This work presents a facile sol-gel technique that can be widely used to convert various carbon-rich bio-structures into different materials. Lotus root, a biomorphic template with high porosity at varying length scales, was selected as the example to demonstrate this approach. The experiment was conducted by infiltrating precursors - titanium (IV) n-butoxide (TnBT) and acetic acid calcium solution - into the lotus root template under vacuum system, followed by calcination. After the treatment, the replicas were calcite CaCO3 and anatase TiO2. In both CaCO3 and TiO2 replicas, the intact structure of the template was preserved. In spite of the overall similarity of the CaCO3 and TiO2 lotus root replicas, some respective differences were found. TiO2 replica was covered with nanowire bundles of 100-200nm in diameter, formed by preferable crystallization of particles, while CaCO3 replica presented the gradient-distributed pores of 10-100μm, which greatly resembled the microstructure of lotus root template. In the BET result, TiO2 replica was mesoporous structure with pores centralizing in 3-4nm. On the other hand, CaCO3 replica had pores in a wider distribution ranging from micro to macro scale. In addition, the surface area was greatly enhanced in both cases. The synthesized materials with hierarchical biomorphic structures may have great potential for purification applications due to their large specific surface area, photocatalytic property, and high adsorption rate.

Fabrication of 3 D Mesoporous Black TiO2 /MoS2 /TiO2 Nanosheets for Visible-Light-Driven Photocatalysis

A novel 3 D mesoporous black TiO2 (MBT)/MoS2 /MBT sandwich-like nanosheet was successfully fabricated using a facile mechanochemical process combined with an in situ solid-state chemical reduction approach, followed by mild calcination (350 °C) under an argon atmosphere. The MBT/MoS2 /MBT exhibits a 3 D sandwich-like nanosheet structure and heterojunctions are formed at the interfaces between MoS2 and black TiO2 . The significantly narrowed band gap of MBT/MoS2 /MBT is attributed to the introduction of MoS2 and the formed Ti(3+) species in the frameworks. The visible-light photocatalytic degradation rate of methyl orange and the hydrogen production rate are as high as 89.86 % and 0.56 mmol h(-1)  g(-1) , respectively. The introduction of MoS2 and Ti(3+) in the frameworks favors the visible-light absorption and the separation of photogenerated charges, and the 3 D sandwich-like heterojunction structure facilitates the transfer of photogenerated charges.

Large-scale synthesis of stable mesoporous black TiO2 nanosheets for efficient solar-driven photocatalytic hydrogen evolution via an earth-abundant low-cost biotemplate

Stable mesoporous black anatase TiO₂ nanosheets (MBTNs) are synthesized via an earth-abundant low-cost biotemplate method combined with an ethanediamine encircling process, and exhibit excellent solar-driven photocatalytic hydrogen generation.

Hierarchical photocatalysts

The design, fabrication, performance and applications of hierarchical semiconductor photocatalysts are thoroughly reviewed and apprised.

A rational approach towards enhancing solar water splitting: a case study of Au-RGO/N-RGO-TiO2

A rational approach was employed to enhance the solar water splitting (SWS) efficiency by systematically combining various important factors that helps to increase the photocatalytic activity. The rational approach includes four important parameters, namely, charge generation through simulated sunlight absorption, charge separation and diffusion, charge utilization through redox reaction, and the electronic integration of all of the above three factors. The complexity of the TiO2 based catalyst and its SWS activity was increased systematically by adding reduced graphene oxide (RGO) or N-doped RGO and/or nanogold. Au-N-RGO-TiO2 shows the maximum apparent quantum yield (AQY) of 2.46% with a H2 yield (525 μmol g(-1) h(-1)) from aqueous methanol, and overall water splitting activity (22 μmol g(-1) h(-1); AQY = 0.1%) without any sacrificial agent under one sun conditions. This exercise helps to understand the factors which help to enhance the SWS activity. Activity enhancement was observed when there is synergy among the components, especially the simulated sunlight absorption (or one sun conditions), charge separation/conduction and charge utilization. Electronic integration among the components provides the synergy for efficient solar light harvesting. In our opinion, the above synergy helps to increase the overall utilization of charge carriers towards the higher activity.

Polymeric photocatalysts based on graphitic carbon nitride

Semiconductor-based photocatalysis is considered to be an attractive way for solving the worldwide energy shortage and environmental pollution issues. Since the pioneering work in 2009 on graphitic carbon nitride (g-C3N4) for visible-light photocatalytic water splitting, g-C3N4 -based photocatalysis has become a very hot research topic. This review summarizes the recent progress regarding the design and preparation of g-C3N4 -based photocatalysts, including the fabrication and nanostructure design of pristine g-C3N4 , bandgap engineering through atomic-level doping and molecular-level modification, and the preparation of g-C3N4 -based semiconductor composites. Also, the photo-catalytic applications of g-C3N4 -based photocatalysts in the fields of water splitting, CO2 reduction, pollutant degradation, organic syntheses, and bacterial disinfection are reviewed, with emphasis on photocatalysis promoted by carbon materials, non-noble-metal cocatalysts, and Z-scheme heterojunctions. Finally, the concluding remarks are presented and some perspectives regarding the future development of g-C3N4 -based photocatalysts are highlighted.

Ni2+ and Ti3+ co-doped porous black anatase TiO2 with unprecedented-high visible-light-driven photocatalytic degradation performance

A black Ni doped porous TiO₂ were fabricated via an in situ solid-state chemical reduction approach, which exhibited excellent visible-light-driven performance.

Green and low-cost synthesis of PANI–TiO2 nanocomposite mesoporous films for photoelectrochemical water splitting

Green and low-cost synthesis procedure for preparation of PANI/TiO₂ mesoporous nanocomposite films with enhanced photocatalytic performance, thanks to a synergic reaction mechanism between PANI and TiO₂ under UV light irradiation.

A facile and general synthesis strategy to doped TiO2 nanoaggregates with a mesoporous structure and comparable property

A facile and general route was explored to fabricate porous metal-doped TiO₂ nanoaggregates from a titanium glycolate precursor and metal salts, and doping with Co or Ni is an effective approach to improve the photocatalytic efficiency.

Multifunctional Floating Titania-Coated Macro/Mesoporous Photocatalyst for Efficient Contaminant Removal

A multifunctional floating photocatalyst consisting of highly active well-ordered mesoporous TiO₂ (OMT) as a catalyst and polyurethane foam (PUF) as a floating substrate is synthesized successfully through a low-temperature ultrasonic and deposition approach. With the synthesized OMT/PUF composites, the multifunctionality of contaminant adsorption, dye degradation, and heavy metal removal can be achieved simultaneously. The prepared photocatalyst is characterized in detail by X-ray diffraction, Raman spectroscopy, transmission electron microscopy, scanning electron microscopy, and N₂ adsorption. The results indicate that the OMT/PUF presents a hierarchical macro/mesoporous structure, which is favorable for the adsorption and diffusion of pollutants and for the efficient utilization of sunlight. The degradation of several model dyes including rhodamine B, methyl orange, methylene blue, and simultaneous reduction of hexavalent chromium are examined over the floating photocatalysts with sunlight irradiation under certain conditions. A synergistic effect between the degradation of dyes and the reduction of Cr^VI is observed for the dye-Cr^VI coexistence system. This novel floating OMT/PUF photocatalyst is very promising in the field of wastewater treatment.

Facile synthesis of hierarchical porous TiO(2) ceramics with enhanced photocatalytic performance for micropolluted pesticide degradation

In this research, hierarchical porous TiO2 ceramics were successfully synthesized through a camphene-based freeze-drying route. The well-dispersed TiO2 slurries were first frozen and dried at room temperature, followed by high-temperature sintering. The ceramics were analyzed by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. Results indicated that the obtained TiO2 ceramics could inhibit undesirable anatase-to-rutile phase transformation and grain growth even at temperatures as high as 800 °C. In this experiment, optimal compressive strength and porosity of the TiO2 ceramics were produced with the initial TiO2 slurry content of ∼15 wt %. The resultant TiO2 ceramics performed excellently in the photodegradation of atrazine and thiobencarb, and the total organic carbon removal efficiency was up to 95.7% and 96.7%, respectively. More importantly, the TiO2 ceramics were easily recyclable. No obvious changes of the photocatalytic performance were observed after six cycles. Furthermore, the ceramics also effectively degraded other pesticides such as dimethoate, lindane, dipterex, malathion, and bentazone. These hierarchical porous TiO2 ceramics have potential applications in environmental cleanup.