Reduced graphene oxide/TiO2(B) nanocomposite-modified separator as an efficient inhibitor of polysulfide shuttling in Li–S batteries

The shutting effect in lithium–sulfur (Li–S) batteries hinders their widespread application, which can be restrained effectively by a modified separator. In this work, a composite of reduced graphene oxide and beta-phase TiO₂ nanoparticles (RGO/TiO₂(B)) is designed as a separator modification material for improving the electrochemical behavior of Li–S batteries. The TiO₂(B) nanoparticles are in situ prepared and tightly adhere to the RGO layer. A series of examinations demonstrated that the RGO/TiO₂(B)-coated separator efficiently inhibits the polysulfide shuttling phenomenon by the cooperative effect of physical adsorption and chemical binding. Specifically, as modified separators, a comparison between TiO₂(B) and anatase TiO₂(A) each composited with RGO has been conducted. The TiO₂(B) sample not only exhibits a superior blocking character of migrating polysulfides, but also enhances battery electrochemical kinetics by fast Li ion diffusion.

Beta-phase TiO₂ nanoparticles were adhered onto RGO in situ to fabricate a multi-functional separator for high-performance lithium–sulfur (Li–S) batteries.     

Steered polymorphic nanodomains in TiO2 to boost visible-light photocatalytic oxidation

A breakthrough in enhancing visible-light photocatalysis of wide-bandgap semiconductors such as prototypical titania (TiO₂) via cocatalyst decoration is still challenged by insufficient heterojunctions and inevitable interfacial transport issues. Herein, we report a novel TiO₂-based composite material composed of in situ generated polymorphic nanodomains including carbon nitride (C₃N₄) and (001)/(101)-faceted anatase nanocrystals. The introduction of ultrafine C₃N₄ results in the generation of many oxygen vacancies in the TiO₂ lattice, and simultaneously induces the exposure and growth of anatase TiO₂(001) facets with high surface energy. The photocatalytic performance of C₃N₄-induced TiO₂ for degradation of 2,4-dichlorophenol under visible-light irradiation was tested, its apparent rate being up to 1.49 × 10⁻² min⁻¹, almost 3.8 times as high as that for the pure TiO₂ nanofibers. More significantly, even under low operation temperature and after a long-term photocatalytic process, the composite still exhibits exceptional degradation efficiency and stability. The normalized degradation efficiency and effective lifespan of the composite photocatalyst are far superior to other reported modified photocatalysts.

A novel TiO₂-based composite material composed of in situ generated biomimetic polymorphic nanodomains including carbon nitride (C₃N₄) and (001)-/(101)-faceted anatase nanocrystals is reported.     

Synthesis and photocatalytic properties of three dimensional laminated structure anatase TiO2/nano-Fe0 with exposed (001) facets

Three dimensional laminated structure anatase TiO₂/nano-Fe⁰ with exposed (001) facets used as photocatalysts were synthesized by a two-step solvothermal route and a liquid phase reduction deposition method. The resulting samples were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, ultraviolet-visible diffuse reflectance spectroscopy, scanning electron microscopy, transmission electron microscopy and selected-area electron diffraction. Characterization and experimental results indicated that the three dimensional laminated structure of anatase TiO₂ was assembled by two dimensional TiO₂-sheets with a thickness of approximately 30 nm. The three dimensional laminated structure anatase TiO₂/nano-Fe⁰ photocatalysts with improved visible-light responsive capability, high charge-hole mobility, and low electron–hole recombination exhibited higher photocatalytic performance in the photocatalytic degradation of methylene blue. The composite of nano-Fe⁰ and TiO₂ could effectively promote the generation of hydroxyl radicals (˙OH) with a synergistic effect and Photo-Fenton theory. This study provided new insights into the fabrication and practical application of high-performance photocatalysts in degrading organic pollutants.

Three dimensional laminated structure anatase TiO₂/nano-Fe⁰ with exposed (001) facets were successfully synthesized, which exhibited higher photocatalytic performance in the photocatalytic degradation of methylene blue.     

Hierarchically ordered macro–mesoporous anatase TiO2 prepared by pearl oyster shell and triblock copolymer dual templates for high photocatalytic activity

Hierarchically ordered macro–mesoporous anatase TiO₂ is prepared by combining the supramolecular-templating self-assembly of amphiphilic triblock copolymer P123 with a natural pearl oyster shell in a hard-templating process by a facile sol–gel reaction. The obtained materials are characterized by Raman spectroscopy, X-ray diffraction, N₂ adsorption–desorption analysis, scanning electron microscopy, and transmission electron microscopy. The results demonstrate that all TiO₂ materials obtained after calcination at various temperatures are in the anatase phase, and interestingly the resultant ordered structure of both macropores and mesopores are well-preserved after calcination at 350 °C or 450 °C, with the walls of macropores composed of ordered mesopores. However, upon calcination at 550 °C or 650 °C, while the ordered macroporous structures remain well-preserved, the mesoporous structures collapse. The photocatalytic activities of the resulting TiO₂ materials are also evaluated by photodegradation of rhodamine B under UV light irradiation. The prepared TiO₂ calcined at 450 °C shows the highest photocatalytic activity.

Hierarchically ordered macro–mesoporous anatase TiO₂ with photocatalytic activity was prepared using triblock copolymer P123 and natural pearl oyster shell as dual templates.     

Effect of polyethylene glycol on crystal growth and photocatalytic activity of anatase TiO2 single crystals

In order to evaluate the effect of polyethylene glycol (PEG) on the growth of TiO₂ crystals, anatase TiO₂ crystals with different morphologies and structures were synthesized by controlling the content and type of PEG in a solvothermal system. Then, their morphology and structure were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Characterization results show that hydrofluoric acid can promote the formation of high activity (001) facets. Experiments on the effect of PEG on crystal growth show that the low molecular weight PEG (PEG400) can accelerate crystal differentiation and relieve the agglomeration of crystals in the presence of hydrofluoric acid. Besides, according to the experimental results, we found that PEG400 can reduce the agglomeration size and number of TiO₂ polycrystalline particles. Research on the photocatalytic activity proposed that the independence of single crystal and the integrity of (001) facets are the critical factors in advanced oxidation reaction. The resultant anatase TiO₂ single crystals could produce more hydroxyl radicals (˙OH) in the photocatalytic system, which exhibited remarkable photocatalytic performance for the degradation of Acid Red B.

Anatase TiO₂ crystals with different structures were synthesized. Experiments on the effect of polyethylene glycol show that the low molecular weight PEG (PEG400) can accelerate crystal differentiation and relieve the agglomeration of crystals.     

Influence of substrate on the structure of predominantly anatase TiO2 films grown by reactive sputtering

TiO₂ films are grown on LaAlO₃ (001), Si (100) and SiO₂ substrates by reactive radio frequency sputtering. X-ray diffraction (XRD) pole figures revealed important characteristics about the texture and phase distribution on those films. Combined with spectroscopic ellipsometry, the pole figures allowed the analysis of the growth characteristics over the whole volume of the layers. Details in the microstructure of the films were probed using transmission electron spectroscopy. Anatase is the dominating phase in the films grown on all substrates. On TiO₂/LaAlO₃ fims, the mosaicity is very low, so that the pole figure closely resembles that of anatase monocrystals. Detailed inspection of XRD pole figures reveals a small amount of rutile in the TiO₂/LaAlO₃ films. For the growth of TiO₂ onto SiO₂, rutile and brookite phases are also detected. Transmission electron microscopy and XRD results show the formation of anatase {112} twins in films grown on the different substrates, suggesting that the anatase {112} twin mediates the growth of rutile and brookite phases. Optical results are in agreement with the XRD observations: the optical properties of TiO₂/LaAlO₃ films are similar to the ordinary values of bulk anatase crystals, indicating the orientation of the film in the [001] direction, whereas results for TiO₂/SiO₂ are compatible with lower crystalline ordering.

Revealing the crystalline structure of predominantly grown anatase TiO₂ films.     

Electrospun titania fiber mats spin coated with thin polymer films as nanofibrous scaffolds for enhanced cell proliferation

The incorporation of inorganic materials into electrospun nanofibres has recently gained considerable attention for the development of extracellular matrix‐like scaffolds with improved mechanical properties and enhanced biological functions for tissue engineering applications. In this study, polymer‐inorganic composite fibres consisting of poly(2‐ethyl‐2‐oxazoline) (PEOXA) and tetrabutyl titanate as the titanium precursor were successfully fabricated through a combined sol–gel/electrospinning approach. PEOXA/Ti(OR)_n composite fibres were obtained with varying amounts of polymer and titanium precursors. Calcinations of the composite fibres were performed at varying temperatures to produce TiO₂ fibres (TiO₂‐T‐60) with anatase, anatase/rutile mixed phase, and rutile crystal structures. Thin polymer films (i.e., poly(2‐ethyl‐2‐oxazoline) (PEOXA), polycaprolactone (PCL), and poly(methyl methacrylate) (PMMA)) were subsequently deposited onto TiO₂‐T‐60 fibre mats by spin coating to facilitate handling of the electrospun substrates after calcination, which are rather brittle and disintegrate easily, and to probe cell‐materials interactions. The cellular behaviour of mouse L929 fibroblasts after culture periods of 1–5 days was compared on the following fibre scaffolds: PEOXA/Ti(OR)_n, TiO₂‐T‐60 (T = 600, 650, and 700 °C), TiO₂‐T‐60 spin‐coated with thin PCL film (PCL/TiO₂‐T‐60), and pure PCL. The results obtained from in vitro cell culture studies for the lactate dehydrogenase release assay and confocal microscopic visualization pointed out the synergistic interplay between the TiO₂ crystal structure and spin‐coated PCL film in facilitating cell interactions with the scaffold surface. The L929 cells were observed to adhere and proliferate better on the surface of TiO₂‐700‐60 having the rutile structure than on the surfaces of TiO₂‐600‐60 and TiO₂‐650‐60 fibre scaffolds with anatase and anatase/rutile mixed phase structures, respectively.     

Controlling the growth of nanosized titania via polymer gelation for photocatalytic applications

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides). The effect of the gelling agent, such as carboxymethylcellulose (CMC) or alginate (Alg), and the drying routes (conventional drying at room temperature, or freeze-drying) on the properties and photocatalytic performances of nanostructured TiO₂ was examined. The crystallographic structures, and textural and morphological characteristics were investigated by thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy with energy dispersive spectrometry (ESEM-FEG-EDS), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectroscopy (DRS) and N₂ adsorption/desorption isotherms. The as-synthesized samples were fully crystallized and appeared to be highly phase-pure anatase or mixed titania polymorphs, and have a quasi-spherical shape with a particle size ranging from 10.34 to 18.07 nm. Phase-pure anatase was obtained by using alginate as the gelling agent, whereas CMC''s gelation promotes mixed structures. The presence of rutile phase results in a lower bandgap value of 3.04 eV corresponding to 408 nm. Thus, the material absorption wavelength shifts slightly from the UV (190–380 nm) to visible region (380–750 nm). The drying process also affects TiO₂ properties. The lyophilization route improves the oxide''s specific surface area, and also its photocatalytic properties verified during Orange G dye photodegradation study.

Nanocrystalline titania was synthesized by a simple, innovative and eco-friendly gelation method by using biopolymers (polysaccharides).     

The effect of graphitized carbon on the adsorption and photocatalytic degradation of methylene blue over TiO2/C composites

The TiO₂/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO₄)₂ and flour. All TiO₂/C composites displayed mesoporous structures with high BET surface areas (117–138 m² g⁻¹) and small crystal sizes of TiO₂ (8–27 nm). The contents of graphitic carbon and rutile TiO₂ increased, while the surface area and TiO₂ crystal size decreased for the TiO₂/C composite on increasing the calcination temperature from 650 to 800 °C; when calcinated at 800 °C, the anatase TiO₂ completely changed into rutile TiO₂ in the TiO₂/C composite. The TiO₂/C composite calcinated at higher temperatures exhibited better adsorptive and photocatalytic degradation performance in the removal of methylene blue (MB). For the entire rutile TiO₂/C-800 composite, the adsorption process of MB can be well described by the pseudo-second-order kinetic model and is governed by chemical adsorption with the maximum adsorption capacity value equal to about 15 mg g⁻¹. Under continuous illumination with a 254 nm UV lamp (15 W) for 3 h, the percentage of MB (14 mg l⁻¹) photocatalytic degradation on 50 mg of TiO₂/C-800 was 25.1% higher than that of the maximum adsorption removal. These results suggest that the graphitized carbon has a significant effect on the adsorptivity and photocatalytic activity of the TiO₂/C composite.

The TiO₂/C composites with approximately 40 wt% of carbon were prepared by calcination of precursors, formed from a one-pot liquid phase reaction between Ti(SO₄)₂ and flour.     

Significant improvement in TiO2 photocatalytic activity through controllable ZrO2 deposition

ZrO₂ was deposited on anatase TiO₂ nanoparticles using 5–80 cycles of atomic layer deposition (ALD). The photocatalytic activity of all samples was evaluated based on the degradation of methylene blue (MB) solution under UV light. The TiO₂ sample with 45 cycles of ZrO₂ deposition (45c-Zr/TiO₂, 1.1 wt% ZrO₂) was proved to be the most efficient catalyst with a degradation kinetic constant 10 times larger than that of the pure TiO₂ sample. All samples were characterized using inductively coupled plasma atomic emission spectroscopy (ICP-AES), nitrogen adsorption–desorption, X-ray diffraction (XRD), transmission electron microscopy (TEM), UV-vis diffuse reflectance spectra analysis (UV-DRS), Raman and photoluminescence (PL) techniques. The high photocatalytic activity of 45c-Zr/TiO₂ can be attributed to stronger adsorption in the ultraviolet region and a reduction in the recombination rate of electron/hole pairs.

The photocatalytic activity of ZrO₂ deposited anatase TiO₂ nanoparticles was evaluated based on the degradation of methylene blue solution under UV light.     

Crystalline phase regulation of anatase–rutile TiO2 for the enhancement of photocatalytic activity

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source. The influences of H₂O₂ volume on anatase and rutile contents and photocatalytic activity of biphasic TiO₂ were investigated and the photocatalytic mechanism was explored. X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-vis diffuse reflectance spectroscopy (UV-vis DRS) and specific surface area (BET) were employed to characterize crystal structure, physical morphology, absorbable light, chemical composition, specific surface area and pore size distribution. The photocatalytic degradation efficiency towards a methylene blue (MB) solution under xenon light was tested, and the photocatalytic stability of the sample was investigated by photocatalytic cycle experiments. The prepared biphasic TiO₂ was nanorod-shaped and had a large specific surface area. The results showed the anatase TiO₂ content increased and the photocatalytic efficiency was enhanced as the H₂O₂ volume solution increased. Among the catalysts, the biphasic TiO₂ prepared with 30 mL of H₂O₂ had the best photocatalytic effect and could entirely degrade the MB solution after 30 minutes under irradiation. After three repeated degradations, the photocatalytic degradation rate was still estimated to be as high as 95%. It is expected that the work will provide new insights into fabricating heterophase junctions of TiO₂ for environmental remediation.

Biphasic TiO₂ with adjustable crystalline phases was prepared by the hydrothermal-calcination method assisted by nitric acid (HNO₃) and hydrogen peroxide (H₂O₂), using potassium titanate oxalate (K₂TiO(C₂O₄)₂) as the titanium source.     

Structural and magnetic study of undoped and cobalt doped TiO2 nanoparticles

The present study investigates the influence of cobalt doping on the structural and magnetic properties of TiO₂ nanoparticles prepared by a simple wet chemical method. The single phase anatase structure of Co-doped TiO₂ nanoparticles was confirmed by X-ray powder diffraction. A morphological study using scanning electron microscopy and transmission electron microscopy indicates the formation of TiO₂ nanoparticles of sizes 6–10 nm. The high resolution TEM image shows clear lattice fringes indicating the highly crystalline nature of the nanoparticles which was further analysed by selected area electron diffraction pattern which indicates a polycrystalline nature of anatase TiO₂. The shifting and broadening of the most intense E_g (1) mode in micro-Raman study of Co-doped TiO₂ nanoparticles and XPS spectra indicate the incorporation of Co in TiO₂. Magnetic measurement shows ferromagnetic behavior at room temperature in undoped TiO₂ which has originated due to the presence of oxygen vacancies which are intrinsic in nature. But the M–H curve of Co-doped TiO₂ shows the coexistence of ferromagnetic and paramagnetic phases with enhanced magnetization. The enhancement in magnetization has arisen due to Co doping and the paramagnetism may be due to the presence of some undetected clusters of oxides of cobalt.

The present study investigates the influence of cobalt doping on the structural and magnetic properties of TiO₂ nanoparticles prepared by a simple wet chemical method.     

Whether planar or corrugated graphitic carbon nitride combined with titanium dioxide exhibits better photocatalytic performance?

The density functional theory method was performed to study the electronic structures of planar (pGN), corrugated (cGN) graphitic carbon nitride and their interactions with titanium dioxide cluster (TiO₂)₇. The transfer of photoinduced electrons was analyzed and electronic excitations were calculated. The obtained results show that cGN is thermodynamically more stable than pGN. cGN chemically interacts with titanium dioxide clusters, while the interaction between pGN and the cluster is assigned to physical nature. The combination of cGN and pGN with (TiO₂)₇ reduces the energy of the first excited states compared to that of the pure substances. The photocatalytic activities were estimated based on hypotheses on the location of the reduction and oxidation sites, the distance between the photoinduced holes and electrons and the electron density of molecular orbitals involved in the excitation. cGN/TiO₂ is predicted to have a higher photocatalytic activity than pGN/TiO₂.

The density functional theory method was performed to study the electronic structures of planar (pGN), corrugated (cGN) graphitic carbon nitride and their interactions with titanium dioxide cluster (TiO₂)₇.     

Enhanced absorption of TiO2 nanotubes by N-doping and CdS quantum dots sensitization: insight into the structure

Anodization of titanium film sputtered on fluorine doped tin oxide (FTO) glass was performed to obtain highly ordered ∼2 μm long and ∼60 nm wide TiO₂ nanotubes. The titania films were annealed in ammonia atmosphere to enable the doping with N. The annealing did not affect the nanotubular morphology and the porosity remained open which is a very important requirement for further deposition of CdS quantum dots. The analysis done by transmission electron microscopy (TEM) has shown that the N-doped nanotubes have a smaller interplanar distance as compared to the undoped ones, whose interplanar distance corresponded to anatase phase. This difference was attributed to the N doping and the Sn migration from the substrate, as demonstrated by energy dispersive spectroscopy (EDS) combined with electron energy loss spectroscopy (EELS). The near edge X-ray absorption fine structure (NEXAFS) analysis clearly demonstrated that also the doped TiO₂ film has anatase phase. Regarding the chemical composition of the studied samples, the X-ray photoelectron spectroscopy (XPS) and synchrotron radiation photoelectron spectroscopy (SRPES) analyses have shown that N is incorporated both interstitially and substitutionally in the TiO₂ lattice, with a decreased contribution of the interstitial after ionic sputtering. The shift of the valence band maximum (VBM) position for the doped TiO₂vs. the undoped TiO₂ proved the narrowing of the band gap. The CdS/TiO₂ films show bigger VBM shifting that can be attributed to CdS deposit. Comparing the absorption spectra of the bare undoped and doped TiO₂ samples, it was noticed that the doping causes a red shift from 397 to 465 nm. Furthermore, the CdS deposition additionally enhances the absorption in the visible range (575 nm for undoped TiO₂/CdS and 560 nm for doped TiO₂/CdS films).

A simple two-step procedure to shift the absorption of TiO₂ nanotubes to the visible range.     

Impact of atomic layer deposited TiO2 on the photocatalytic efficiency of TiO2/w-VA-CNT nanocomposite materials

Titanium oxide (TiO₂) has been widely investigated as a photocatalytic material, and the fact that its performance depends on its crystalline structure motivates further research on the relationship between preparation methods and material properties. In this work, TiO₂ thin films were grown on non-functionalized wave-like patterned vertically aligned carbon nanotubes (w-VA-CNTs) via the atomic layer deposition (ALD) technique. Grazing incidence X-ray diffraction (GIXRD) analysis revealed that the structure of the TiO₂/VA-CNT nanocomposites varied from amorphous to a crystalline phase with increasing deposition temperature, suggesting a “critical deposition temperature” for the anatase crystalline phase formation. On the other hand, scanning transmission electron microscopy (STEM) studies revealed that the non-functionalized carbon nanotubes were conformally and homogeneously coated with TiO₂, forming a nanocomposite while preserving the morphology of the nanotubes. X-ray photoelectron spectroscopy (XPS) provided information about the surface chemistry and stoichiometry of TiO₂. The photodegradation experiments under ultraviolet (UV) light on a model pollutant (Rhodamine B, RhB) revealed that the nanocomposite comprised of anatase crystalline TiO₂ grown at 200 °C (11.2 nm thickness) presented the highest degradation efficiency viz 55% with an illumination time of 240 min. Furthermore, its recyclability was also demonstrated for multiple cycles, showing good recovery and potential for practical applications.

Amorphous or anatase crystalline TiO₂/VA-CNT nanocomposites were grown controlling the synthesis temperature. Photocatalytic degradation of RhB of 55% was achieved after 240 min. The immobilized material remains active after 4 cycles of use.     

Synthesis of 3D flower-like structured Gd/TiO2@rGO nanocomposites via a hydrothermal method with enhanced visible-light photocatalytic activity

In this study, novel Gd/TiO₂@rGO (GTR) nanocomposites with high photocatalytic performance were fabricated via a one-pot solvothermal approach. During the preparation step, graphene oxide (GO) was reduced to reduced graphene oxide (rGO), and subsequently, on the surfaces of which anatase TiO₂ doped with Gd metal was grown in situ with a 3D petal-like structure. Gd doping into the classical TiO₂@rGO system efficiently expands the absorption range of light, improves the separation of photogenerated electrons, and increases the photocatalytic reaction sites. The specific surface areas, morphological structures, and valence and conduction bands of the obtained GTR nanocomposites were analyzed and correlated with their enhanced photocatalytic performances for the degradation of an aqueous RhB solution. The experimental results indicated that the best performance was achieved with the 3% GTR composite, which exhibited the highest photoelectrocatalytic activity because of two aspects: the rapid separation of electrons and holes, and improvement in adsorption capacity. As compared with pure TiO₂, the GTR composites demonstrated enhanced photoactivity due to synergetic effects between the effective photo-induced electron transfer from TiO₂ to the surface of the rGO acceptor through interfacial interactions and the variation of structure and electrons under the adoption of Gd.

One-pot green synthesis of 3D flower-like structured Gd/TiO₂@rGO nanocomposites via a hydrothermal method with high photocatalytic activity.     

Effect of triblock copolymers on crystal growth and the photocatalytic activity of anatase TiO2 single crystals

In order to evaluate the effect of a triblock copolymer on the growth of TiO₂ crystals, anatase TiO₂ crystals with different morphologies and structures were synthesized by controlling the content and type of triblock copolymer in the solvothermal route. The resulting samples were characterized by XRD, XPS, SEM, TEM and EDX. The characterization results show that hydrofluoric acid can promote the formation of highly active (001) facets by the formation of a Ti–F bond. The triblock copolymers (P123 and F127) refine the surface structure of polycrystalline spherical TiO₂ and make the crystal surface homogeneous and smooth. Moreover, P123 causes the agglomeration effect and hinders the recrystallization process of anatase TiO₂ single crystals, and this will lead to corrosion of the crystal facets. Meanwhile, F127 destroys crystal formation and hinders crystal growth due to its special micelle structure. In addition, research on the photocatalytic activity proposed that the integrity of the (001) and (101) facets was a critical factor in the photocatalytic reaction. The resultant anatase TiO₂ single crystals could produce more hydroxyl radicals (˙OH) in the photocatalytic system, which exhibited remarkable photocatalytic performance for the degradation of three types of dye.

The effects of triblock copolymers (P123 and F127) on the growth of TiO₂ crystals were studied. Anatase TiO₂ crystals with different morphologies and structures were synthesized by controlling the content and type of triblock copolymer in a solvothermal method.     

CNT–TiO2 core–shell structure: synthesis and photoelectrochemical characterization

Porous composite coatings, made of a carbon nanotube (CNT)–TiO₂ core–shell structure, were synthesized by the hybrid CVD-ALD process. The resulting TiO₂ shell features an anatase crystalline structure that covers uniformly the surface of the CNTs. These composite coatings were investigated as photoanodes for the photo-electrochemical (PEC) water splitting reaction. The CNT–TiO₂ core–shell configuration outperforms the bare TiO₂ films obtained using the same process regardless of the deposited anatase thickness. The improvement factor, exceeding 400% in photocurrent featuring a core–shell structure, was attributed to the enhancement of the interface area with the electrolyte and the electrons fast withdrawal. The estimation of the photo-electrochemically effective surface area reveals that the strong absorption properties of CNT severely limit the light penetration depth in the CNT–TiO₂ system.

CNT–TiO₂ core–shell nanostructured coatings were made using a hybrid CVD/ALD process. The evaluation of these films as photoanodes for the photoelectrochemical water splitting reaction reveals a clear benefit from the involvement of CNTs.     

Stabilized fabrication of anatase-TiO2/FeS2 (pyrite) semiconductor composite nanocrystals for enhanced solar light-mediated photocatalytic degradation of methylene blue

A novel visible light active TiO₂/FeS₂ semiconductor photocatalyst was synthesized by a simple wet chemical process. X-ray diffraction (XRD) was used to analyze the anatase TiO₂ and pyrite structures in FeS₂/TiO₂ nanocrystals. Scanning electron microscopy (SEM) confirmed the spherical morphology of composite nanocrystals. X-ray photoelectron spectroscopy (XPS) identified the Fe²⁺, S¹⁻, Ti⁴⁺, and O²⁻ oxidation states of relevant species. Energy dispersive X-ray (EDX) analysis was performed for compositional analysis. The measured band gap of the TiO₂/FeS₂ nanocomposite system was 2.67 eV, which is smaller than un-doped TiO₂ (3.10 eV) and larger than FeS₂ (1.94 eV). The photocatalytic activity of TiO₂/FeS₂ was significantly higher than pure FeS₂ for degrading methylene blue (MB) under solar light irradiation due to the increase in visible light absorption, reduction in band gap energy, and better election–hole pair separation. The photocatalytic degradation of MB was investigated under the influence of solution pH, dye concentrations, and varied catalyst dosage. The optimum degradation (100%) of MB was observed in 180 min and the photocatalysis of MB reduced as the dye concentrations in the solution increased from 15 to 75 mg L⁻¹. These results prove that the TiO₂/FeS₂ nanocomposite has the stability, recycling, and adaptability for its practical application as a visible light photocatalyst for wastewater treatment. TiO₂/FeS₂ showed increased degradation of the organic pollutant; which is confirmed by the increased rate of chemical reaction following pseudo first-order reaction kinetics with the highest rate constant value of 0.0408 m⁻¹ having highest R² value of 0.9981.

A novel visible light active TiO₂/FeS₂ semiconductor photocatalyst was synthesized by a simple wet chemical process.     

Real roles of perylene diimides for improving photocatalytic activity

Three novel visible-light-driven composite photocatalysts: five-membered O-heterocyclic annulated perylene diimide doped TiO₂ (PDI-1/TiO₂), 1-phenol-N,N′-dicyclohexyl perylene-3,4,9,10-tetracarboxylic diimide doped TiO₂ (PDI-2/TiO₂), and N,N′-dicyclohexyl perylene diimide doped TiO₂ (PDI-3/TiO₂), were synthesized using a hydrothermal synthesis method. The effects of introducing PDIs with different structures into TiO₂ were evaluated by assaying the photodegradation rate of Methylene Blue (MB). The photoactivities of the PDI-1/TiO₂ and PDI-2/TiO₂ catalysts were better than that of PDI-3/TiO₂. This is because the large surface area of PDI-1 nanorods and PDI-2 nanobelts extended the 1D charge carrier channel, which facilitated electron transfer to the TiO₂ surface and improved the photocatalytic activity of the composites. The PDI-1/TiO₂ composite showed the highest photoactivity, and the activity remained at 86.4% after four reuse cycles. The extended π–π stacking of self-assembled PDI-1 and the strong interactions between self-assembled PDI-1 and TiO₂ played significant roles in accelerating charge transfer and decreasing recombination of photogenerated electron–hole pairs. The steric hindrance of the phenoxy substituent at the bay position of PDI-2 prevented the PDI-2 nucleus from contacting TiO₂ and weakened the interaction between PDI-2 and TiO₂, which further resulted in the low photoactivity of PDI-2/TiO₂. This work provides a practical way to improve the performances of traditional organic and inorganic composite photocatalysts.

Three novel visible-light-driven composite photocatalysts were synthesized by hydrothermal method. The effects of introducing PDIs with different structures into TiO₂ were evaluated by assaying the photodegradation rate of methylene blue.