Optimizing the Photocatalytic Properties of Hydrothermal TiO2by the Control of Phase Composition and Particle Morphology. A Systematic Approach

Exploring Structural and Optical Properties of Iodine-Doped TiO2 Nanoparticles in Rhodamine-B Dye Degradation: Experimental and Theoretical Investigation

Energy conversion and pollutant degradation are critical for advancing sustainable technologies, yet they often encounter challenges related to charge recombination and efficiency limitations. This study explores iodine-doped TiO2 nanoparticles as a potential solution for enhancing both energy conversion and pollutant degradation. The nanoparticles were synthesized via the sol-gel method with varying iodine precursor concentrations (0.025 to 0.1 M) and were characterized for their structural, compositional, and optical properties, particularly in relation to their photocatalytic performance in Rhodamine-B dye degradation. X-ray diffraction confirmed a tetragonal anatase crystal structure, with the average crystallite size decreasing from 10.06 nm to 8.82 nm with increase in iodine concentration. Selected area electron diffraction patterns verified the polycrystalline nature of the nanoparticles. Dynamic light scattering analysis showed hydrodynamic radii ranging from 95 to 125 nm. Fourier-transform infrared spectroscopy identified metal-oxygen vibrations at 441 cm⁻1, and electron microscopy confirmed the spherical morphology of the nanoparticles. Elemental analysis detected the presence of Ti, O, and I in the samples. Diffuse reflectance spectroscopy indicated the optical absorption edges for the doped samples in the visible region from which the corresponding band gap values were deduced. Photoluminescence spectroscopy revealed that the sample with 0.1 M iodine exhibit the lowest emission intensity, suggesting reduced charge recombination. Notably, 0.1 M iodine doped TiO2 samples demonstrated the highest photocatalytic efficiency, achieving 82.36% degradation of Rhodamine-B dye within 140 minutes under visible light. Additionally, ab-initio density functional theory calculations were performed to investigate the structural, optical, and adsorption properties of TiO2, iodine-doped TiO2, Rhodamine-B, and their composites, providing further insight into the enhanced photocatalytic activity observed in the experiments.

Modification engineering of TiO2-based nanoheterojunction photocatalysts

Titanium dioxide (TiO2)-based photocatalysts have gained increasing attention for their versatile applications in organic degradation, hydrogen production, air purification, and CO2 reduction. Various TiO2-based heterojunction structures, including type I, type II, Schottky junction, Z-scheme, and S-scheme, have been extensively studied. The current research frontier is centered on the engineering modifications of TiO2-based nanoheterojunction photocatalysts, such as defect engineering, morphological engineering, crystal phase/facet engineering, and multijunction engineering. These modifications enhance carrier transport, separation, and light absorption, thereby improving the photocatalytic performance. Remarkably, this aspect has been less addressed in existing reviews. This review aims to fill this gap by focusing on the engineering modifications of TiO2-based nanoheterojunction photocatalysts. We delve into specific topics like oxygen vacancies, n-p homojunctions, and double defects. The review also systematically discusses the applications of multidimensional heterojunctions and examines carrier transport pathways in heterophase/facet junctions and their interactions with heterojunctions. A comprehensive summary of multijunction systems, including multi-Schottky junctions, semiconductor-based heterojunction-attached Schottky junctions, and multisemiconductor-based heterojunctions, is presented. Lastly, we outline future perspectives in this promising research field. This paper will assist researchers in constructing more efficient TiO2-based nanoheterojunction photocatalysts.

Multimodal energy harvesting and catalysis of piezoelectric nanosheets for efficient and round-the-clock wastewater treatment

Solar-driven pollutants degradation is an important way for green wastewater treatment, but it is still limited by the intermittent solar flux. Here, we have prepared piezoelectric Bi4Ti3O12 (BTO) nanosheets with abundant physical properties, which can convert extensive solar energy, mechanical energy and temperature variation energy into electrical and chemical energy. It can be used for round-the-clock wastewater treatment by harvesting multi-modal energy. More importantly, the degradation rate of piezoelectric nanosheets can reach 153.4 × 10-3 min-1, and nanosheets can degrade many organic pollutants. In addition, we fabricate porous foam catalysts based on BTO-polydimethylsiloxane (PDMS) composite to prevent secondary contamination. Our results suggest that BTO nanosheets with photoelectric, piezoelectric and pyroelectric catalysis offer a potential approach for round-the-clock wastewater degradation by harvesting solar energy, ambient mechanical energy, and cyclic thermal energy.

A Comparative Study in the Design of TiO2 Assisted Photocatalytic Coatings Monitored by Controlling Hydrophilic Behavior and Rhodamine B Degradation

This work presents a comparative study related to the photocatalytic efficiency associated with wettability measurements and organic dye degradation, as well as other relevant properties (i.e., corrosion resistance, roughness, wettability, and adhesion to a substrate). The photocatalytic precursors are titanium dioxide nanoparticles (TiO₂ NPs) which are dispersed onto a polymeric electrospun fiber matrix by using three different deposition techniques such as electrospraying, spraying, and dip-coating, respectively. In this work, the host electrospun matrix is composed of poly(acrylic acid) fibers crosslinked with cyclodextrin (β-CD), which shows a good chemical affinity and stability with the other deposition techniques which are responsible for incorporating the TiO₂ NPs. In order to evaluate the efficacy of each coating, the resultant photocatalytic activity has been monitored by two different tests. Firstly, the reduction in the water contact angle is appreciated, and secondly, the degradation of an organic dye (Rhodamine B) is observed under UV irradiation. In addition, the final roughness, adherence, and pitting corrosion potential have also been controlled in order to determine which solution provides the best combination of properties. Finally, the experimental results clearly indicate that the presence of TiO₂ NPs deposited by the three techniques is enough to induce a super hydrophilic behavior after UV irradiation. However, there are notable differences in photocatalytic efficiency on the Rhodamine B as a function of the selected deposition technique.

Hepatic proteomic assessment of oral ingestion of titanium dioxide nano fiber (TDNF) in Sprague Dawley rats

Titanium dioxide nanofibers (TDNF) have been widely employed in pigments, sunscreens, paints, ointments, toothpaste and photocatalytic splitting of water. However, their potential toxicity has not been thoroughly examined. The goal of the present study is to examine hepatic effects associated with the ingestion of TDNF. TDNF was fabricated via electrospinning method and characterized. Six to seven weeks old male Sprague Dawley rats ingested (oral gavage) a total of 0 ppm, 40, 60 ppm TDNF for two weeks. After sacrifice, the liver was assessed for cellular effects using proteomic approach. The fibers diameter ranged from 0.18 - 0.29 μm, forming clusters and majority of the fibers were in the rutile phase. Proteomics assessment revealed more that more than 400 hundred proteins in the liver may be affected. These proteins are involved in such processes as catalysis of fatty acids by CoA, homocysteine metabolism, beta oxidation and the condensation of carbamoyl phosphate in the urea cycle among others. Further analysis of the protein associations showed that 325 biological processes, 140 molecular functions and 70 cellular components appear to be affected from the ingestion of TNDF. Quantitative analysis of specific mRNA transcripts indicated CMBL, GSTM1 and SDS were differentially expressed.

Lead-Free Bi0.5Na0.5TiO3 Ferroelectric Nanomaterials for Pyro-Catalytic Dye Pollutant Removal under Cold-Hot Alternation

In this work, explicitly pyro-catalytic performance is observed in sol-gel-synthesized ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials, and its application for dye wastewater purification is also actualized under temperature fluctuations varying from 23 °C to 63 °C. The decomposition ratios of the pyro-catalytic Bi_0.5Na_0.5TiO₃ nanomaterials on Rhodamine B, methyl blue and methyl orange can reach 96.75%, 98.35% and 19.97%, respectively. In the pyro-catalytic process, the probed active species such as hydroxyl radicals, superoxide radicals and holes play an extremely important role in decomposing dye molecules. The ferroelectric Bi_0.5Na_0.5TiO₃ lead-free nanomaterials will have an excellent prospect for dye wastewater purification due to its explicit pyro-catalysis.

Defect-assisted photocatalytic activity of glass-embedded gallium oxide nanocrystals

The use of glassceramics in photocatalysis is an attractive option for the realization of smart optical fibers and self-cleaning windows. Here we present the photocatalytic activity of germanosilicate glasses embedding Ga₂O₃ nanocrystals prepared by batch melting and glass heat treatment. The powdered material is used for UV-assisted degradation of rhodamine in water. The kinetics show changes after repeated experiments. In the first cycle, the apparent rate is governed by a second-order reaction with a Gaussian-like shape, whereas the second cycle follows a first-order reaction. The modification appears to be correlated with perturbations in the defect population. Photoluminescence has been used to monitor the evolution of such defects. Kinetic data on photoreactions and defect formation have been modelled in a combined frame in which the defect concentration determines the photocatalytic activity. The results prove the photocatalytic ability of the studied glassceramics. Moreover, the general validity of the kinetic model can be of interest for other systems in which the photocatalytic response depends on photoreactive species concentration.

Recent advancements of g-C3N4-based magnetic photocatalysts towards the degradation of organic pollutants: a review

Heterogeneous photocatalysis premised on advanced oxidation processes has witnessed a broad application perspective, including water purification and environmental remediation. In particular, the graphitic carbon nitride (g-C₃N₄), an earth-abundant metal-free conjugated polymer, has acquired extensive application scope and interdisciplinary consideration owing to its outstanding structural and physicochemical properties. However, several issues such as the high recombination rate of the photo-generated electron-hole pairs, smaller specific surface area, and lower electrical conductivity curtail the catalytic efficacy of bulk g-C₃N₄. Another challenging task is separating the catalyst from the reaction medium, limiting their reusability and practical applications. Therefore, several methodologies are adopted strategically to tackle these issues. Attention is being paid, especially to the magnetic nanocomposites (NCs) based catalysts to enhance efficiency and proficient reusability property. This review summarizes the latest progress related to the design and development of magnetic g-C₃N₄-based NCs and their utilization in photocatalytic systems. The usefulness of the semiconductor heterojunctions on the catalytic activity, working mechanism, and degradation of pollutants are discussed in detail. The major challenges and prospects of using magnetic g-C₃N₄-based NCs for photocatalytic applications are highlighted in this report.

Recent developments in photocatalytic degradation of insecticides and pesticides

Widespread use of pesticides in agricultural and domestic sectors and their long half-life have led to their accumulation in the environment beyond permissible limits. Advanced chemical oxidation methods including photocatalytic degradation are being widely investigated for their mineralization. Photocatalytic degradation is the most promising method for degrading pesticides as well as other organic pollutants. Titanium dioxide with or without modification has been widely used as the photocatalyst. Some research groups have also tried other photocatalysts. This review presents a critical summary of the research results reported during the past two decades as well as the scope for future research in this area.

New insights for titanium(iv) speciation in acidic media based on UV-visible and 31P NMR spectroscopies and molecular modeling

Titanium chemistry in aqueous acidic media has been extensively investigated over the last decades. Hydrolyzed species such as Ti(OH)³⁺, TiO²⁺, Ti(OH)₂²⁺ or Ti(OH)₃⁺ have been identified and their equilibria have been studied in nitric and perchloric acid. A predominance of the divalent cations was found for low pH (i.e., pH <2). Nonetheless, recent literature reports the existence of small titanium oxo-clusters in aqueous acidic media for large titanium(iv) concentration (typically., >0.1 mol L⁻¹), as stable precursors for the formation of condensed titanium dioxide. The present paper reconsiders firstly previous knowledge about the speciation of titanium(iv) in non-complexing acidic media by giving evidence for the presence of polynuclear hydrolyzed species, even at very low Ti(iv) concentration (i.e., typically <0.1 mmol L⁻¹). UV-visible absorbance spectra recorded for diluted nitric acid solutions (a model of non-complexing acidic medium) containing titanium(iv) were compared to time-dependent density functional theory (TD-DFT) predicted excitation energies. Experimental and predicted maximal absorbance wavelengths showed significantly improved matches when polynuclear species were considered in TD-DFT calculation. Then, 0.1–12.7 mol L⁻¹ phosphoric acid solutions containing titanium(iv) were studied by means of spectroscopic techniques (UV-visible, NMR) in order to identify qualitatively the presence of titanium(iv) complexes and to link this speciation to the acid concentration. Two different titanium(iv) orthophosphate complexes, potentially polynuclear, were detected, and the presence of free titanium(iv) is also expected for low phosphoric acid concentration (i.e., <0.1 mol L⁻¹). A general complexation scheme for a large range of H₃PO₄ concentration was thus formulated.

A spectroscopic study of titanium(iv) speciation in diluted nitric acid (model of non-complexing medium) and 0.1–12.7 mol L⁻¹ phosphoric acid aqueous solutions. Evidence for the presence of polynuclear species is supported by molecular modeling.

In situ chloride-mediated synthesis of TiO2 thin film photoanode with enhanced photoelectrochemical activity for carbamazepine oxidation coupled with simultaneous cathodic H2 production and CO2 conversion to fuels

This study investigated the simultaneous photoelectrochemical (PEC) degradation of carbamazepine (CBZ), reduction of CO₂ and production of H₂ using a TiO₂ thin film as photoanode and Ag plate as cathode. The photoanode was fabricated using sequential hydrothermal and calcination processes. The use of chloride during the hydrothermal process enhanced formation of oxygen vacancies and defects on the TiO₂ surface. Calcination not only further strengthened those features but also enhanced the crystallinity and anatase/rutile ratio, endowing the TiO₂ photoanode with superior PEC capacity. Characterization of physicochemical and PEC properties revealed that photogenerated electrons-holes were rapidly generated and efficiently separated on the TiO₂ surface during the PEC process. Hydroxyl radicals were the main active species responsible for anodic oxidation of carbamazepine, while hydrogen radicals and carbon dioxide radical anions mediated CO₂ reduction and H₂ production in the cathodic process. This work confirms the suitability of the prepared TiO₂ photoanode for PEC degradation of organic pollutants coupled with CO₂ reduction and H₂ production.

Improved direct synthesis of TiO2 catalyst using sonication and its application for the desulfurization of thiophene

TiO₂ catalyst was synthesized in the presence of ultrasound (ultrasonic horn at 20 kHz frequency and 70% duty cycle) at different power (80 W to 120 W) and durations as well as surfactant concentration with an objective of establishing best conditions for achieving lowest particle size of the photocatalyst. Detailed characterization in terms of crystal phase, crystallinity, functional groups and morphology of the photocatalyst has been performed using SEM, XRD and FTIR analysis. It was demonstrated that sonication significantly reduced the particle size with high degree of sphericity and homogeneity as compared to conventionally synthesized TiO₂ with similar crystallinity in both cases. The catalytic performance was subsequently evaluated for the deep desulfurization of thiophene. Different desulfurization approaches including individual US (ultrasonic horn at 20 kHz frequency, 110 W power and 70% duty cycle) and UV irradiations, US/UV, US/UV/H₂O₂, US/UV/TiO₂ and US/UV/H₂O₂/TiO₂ were applied to evaluate the catalytic activity. The best approach was demonstrated as US/UV/H₂O₂/TiO₂ and also activity of catalyst synthesized using ultrasound was much better compared to conventionally synthesized catalyst. The studies related to different model solvents demonstrated lowest reactivity for toluene whereas n-hexane and n-octane resulted in complete desulfurization in 60 min and 50 min treatment respectively. The desulfurization followed pseudo first order reaction kinetics irrespective of the solvent used. Overall the work clearly demonstrated the efficacy of ultrasound in improving the catalyst synthesis as well as desulfurization of thiophene.

Visible-Light-Responsive Oxyhalide PbBiO2Cl Photoelectrode: On-Site Flux Synthesis on a Fluorine-Doped Tin Oxide Electrode

The performance of photoelectrodes is hugely affected by the preparation method. Although a flux synthesis is useful to endow semiconductor particles with the desired properties such as high crystallinity, there are only a few reports on its application to photoelectrode fabrication, probably because relatively high temperatures are necessary. In the present study, we introduce a new concept for on-site flux synthesis of semiconductor crystals on a commonly used fluorine-doped tin oxide (FTO) substrate; a seed layer is predeposited and then treated with an appropriate flux containing other required elements at a right temperature lower than the limit temperature of FTO but sufficiently high to transform the seed layer to the target material with the aid of flux. Here, an oxyhalide PbBiO₂Cl, one of the promising semiconductors for achieving visible-light water splitting, is selected as a target material. Combination of a BiOCl seed layer and the NaCl-PbCl₂ flux containing other precursors enables the seed layer to transform into PbBiO₂Cl crystals even at 450 °C. The thickness of the PbBiO₂Cl layer can be controlled by changing the thickness of the BiOCl seed layer for efficient photon-to-current conversion. Owing to a good contact at the semiconductor-substrate interfaces as well as the high quality of PbBiO₂Cl crystals, the flux-synthesized PbBiO₂Cl photoelectrode shows a significantly improved PEC performance compared with those prepared from the particulate PbBiO₂Cl samples via the conventional squeegee method. In addition, the present PbBiO₂Cl photoelectrodes exhibit both anodic and cathodic photoresponses with substantially high current values depending on the applied potentials; the unusual phenomenon is affected by the conditions in flux-assisted synthesis. The present study provides a new and effective way for fabricating efficient photoelectrodes of various semiconductors on various substrates and a possible option to control their morphologies and p/n types for further improvement in performance.

Photocatalytic degradation of methylene blue under UV and visible light by brookite–rutile bi-crystalline phase of TiO2

Brookite–rutile bi-crystalline phase of TiO₂ were synthesized and applied for the degradation of methylene blue under UV and visible light irradiation by photocatalytic reaction.

Hydrothermal synthesis of novel 1-aminoperylene diimide/TiO2/MoS2 composite with enhanced photocatalytic activity

1-aminoperylene diimide/TiO2/MoS2 composite (NH2-PDI/TiO2/MoS2) with ordered structure was prepared by hydrothermal synthesis method. The composite was characterized by XRD, SEM, FTIR, XPS, BET, DRS, PL, EIS, Raman, photocurrent, and Mott-Schottky plots spectroscopy. The potential positions of the conduction and valence bands, and the band gap energy of the semiconductors were estimated. The composite exhibited higher photocatalytic activity compared with the mono-component systems. The apparent rate constants (k) were determined as 0.00616, 0.00352, 0.00738, 0.00517, 0.00752, and 0.00806 min-1 for TiO2, NH2-PDI, NH2-PDI/TiO2, MoS2, MoS2/TiO2, and NH2-PDI/TiO2/MoS2, respectively. The detection of radical scavengers confirmed that superoxide radicals, photogenerated holes, and photogenerated electrons were the main active substances for MB degradation. Between type II- heterojunction mechanism and Z-scheme mechanism, the latter could explain the enhanced photocatalytic activity of the composite better. The Z-scheme mechanism accumulates more electrons at CB level of NH2-PDI and hence generates more super oxide radicals.

Highly Active Rutile TiO2 Nanocrystalline Photocatalysts

The controllable synthesis of rutile TiO₂ single crystal particles with the preferential orientation of {111} facets still remains a scientific and technological challenge. Here, we developed a facile route for fabrication of rutile TiO₂ nanorod crystals (RTiO₂NRs) having high ratios of oxidative {111} to reductive {110} surfaces. RTiO₂NRs were synthesized using a peroxo-titanium complex (PTC) approach, which was controlled by changing the Ti/H₂O₂ ratio. The thus obtained RTiO₂NRs revealed a high tendency to agglomerate through orientation-dependent attachment along the {110} facets. This resulted in an increased {111}/{110} surface ratio and led to a markedly improved photocatalytic activity of RTiO₂NR aggregates. The reported findings illustrate the rich potential of the herein proposed facile and energy-efficient synthesis of nanostructured rutile TiO₂-based photocatalysts.

Metal-enhanced fluorescence detection and degradation of tetracycline by silver nanoparticle-encapsulated halloysite nano-lumen

The ultrasensitive detection and efficient degradation of tetracycline (TC) residues are important for improving food safety and protecting human health. In this paper, a smart silver-enhanced fluorescence platform for the ultrasensitive detection of TC was constructed via a simple and selective modification of the interior and external tubes of natural halloysite nanotubes. The thick pipe wall of this platform provides a natural defense and promotes metal-enhanced fluorescence effects, which subsequently accelerates the detection of TC. Moreover, the nanoplatform of the modified Ag nanoparticles can induce the separation of electrons and holes, thereby enhancing photocatalytic activity in TC degradation. This platform provides new opportunities for studying natural halloysite nanotubes and for simultaneously detecting and photodegrading other deleterious substances.

Photocatalytic activity of NiFe2O4 and Zn0.5Ni0.5Fe2O4 modified by Eu(III) and Tb(III) for decomposition of Malachite Green

The mixed metal oxides NiFe2O4 and Zn0.5Ni0.5Fe2O4 with a spinel-like structure, pure and modified with the lanthanide ions Eu(III) and Tb(III), were prepared by a sol-gel process in which propylene oxide was used as a gelling agent and then tested as photocatalysts. The photocatalytic activity was studied under polychromic visible light irradiation (halogen lamp) for the decomposition of the water pollutant Malachite Green in model solutions which were prepared under laboratory conditions. The modified samples showed a better activity under visible light irradiation than the pure samples. The highest activity under visible light irradiation was observed for Zn0.5Ni0.5Fe2O4 that was modified with 5 wt. % Eu(III) or Tb(III), and which showed the positive effects of the doping ions. Based on the cartographic data for the smooth and equal distribution of Tb(III) on the surface of Zn0.5Ni0.5Fe2O4 particles, the surface processes may have influenced the photocatalytic activity. The energy band gap of the samples was calculated, showing somewhat lower values for the doped samples than the pure ferrites.

Facile Formation of Anatase/Rutile TiO2 Nanocomposites with Enhanced Photocatalytic Activity

Anatase/rutile mixed-phase TiO₂ nanoparticles were synthesized through a simple sol-gel route with further calcination using inexpensive titanium tetrachloride as a titanium source, which effectively reduces the production cost. The structural and optical properties of the prepared materials were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and UV-vis adsorption. The specific surface area was also analyzed by Brunauer-Emmett-Teller (BET) method. The anatase/rutile mixed-phase TiO₂ nanocomposites containing of rod-like, cuboid, and some irregularly shaped anatase nanoparticles (exposed {101} facets) with sizes ranging from tens to more than 100 nanometers, and rod-like rutile nanoparticles (exposed {110} facets) with sizes ranging from tens to more than 100 nanometers. The photocatalytic activities of the obtained anatase/rutile mixed-phase TiO₂ nanoparticles were investigated and compared by evaluating the degradation of hazardous dye methylene blue (MB) under ultraviolet light illumination. Compared to the commercial Degussa P25-TiO₂, the mixed-phase TiO₂ nanocomposites show better photocatalytic activity, which can be attributed to the optimal anatase to rutile ratio and the specific exposed crystal surface on the surface. The anatase/rutile TiO₂ nanocomposites obtained at pH 1.0 (pH1.0-TiO₂) show the best photocatalytic activity, which can be attributed to the optimal heterojunction structure, the smaller average particle size, and the presence of a specific exposed crystal surface. The enhanced photocatalytic activity makes the prepared anatase/rutile TiO₂ photocatalysts a potential candidate in the removal of the organic dyes from colored wastewater.

Recent Progress on Titanium Dioxide Nanomaterials for Photocatalytic Applications

Environmental and energy problems have drawn much attention owing to rapid population growth and accelerated economic development. For instance, photocatalysis, "a green technology", plays an important role in solar-energy conversion owing to its potential to solve energy and environmental problems. Recently, many efforts have been devoted to improving visible-light photocatalytic activity by using titanium dioxide as a photocatalyst as a result of its wide range of applications in the energy and environment fields. However, fast charge recombination and an absorption edge in the UV range limit the photocatalytic efficiency of TiO₂ under visible-light irradiation. Many investigations have been undertaken to overcome the limitations of TiO₂ and, therefore, to enhance its photocatalytic activity under visible light. The present literature review focuses on different strategies used to promote the separation efficiency of electron-hole pairs and to shift the absorption edge of TiO₂ to the visible region. Current synthesis techniques used to elaborate several nanostructures of TiO₂ -based materials, recent progress in enhancing visible photocatalytic activity, and different photocatalysis applications will be discussed. On the basis of the studies reported in the literature, we believe that this review will help in the development of new strategies to improve the visible-light photocatalytic performance of TiO₂ -based materials further.

Fabrication of mixed phase TiO2 heterojunction nanorods and their enhanced photoactivities

Substantial efforts have been made in recent times in solving the major limiting factors affecting the efficiency of a photocatalyst. The fabrication of efficient junction architectures is one of the viable approaches to resolve this setback. We have developed a facile and systematic approach for the synthesis of anatase TiO2 () nanoparticles and 1-D anatase and rutile TiO2 () heterojunction nanorods to enhance the interfacial contact area by adjusting the titanium(iv) butoxide (TBOT) to titanium chloride (TiCl4) volume ratio. Their narrower band gap, increasing surface area and anatase phase composition engineered by adjusting the relative concentrations of titanium butoxide (TBOT) and titanium chloride (TiCl4) (TBOT/TiCl4, 1 : 0, 1 : 0.25, 1 : 1 and 1 : 4 v/v for , , and respectively) are also addressed. The materials showed impressive photocatalytic activity for H2 evolution from water/methanol and the photodegradation of organic pollutants like rhodamine B (RhB) and methylene blue (MB) dyes. showed superior activity (16.4 mmol g(-1) h(-1)) with an apparent quantum efficiency (AQE) of 7.7% together with its long-term stability. This is attributed to the synergistic effect observed in the mixed phase nanorod heterojunction photocatalyst. Methyl viologen (MV(2+)) has been used as a probe to elucidate the photocatalytic activities and highlight the heterojunction driven separation of photo-excited charge carriers for enhanced hydrogen production.

The Effect of Sulphate Anions on the Ultrafine Titania Nucleation

The phenomenological model of sulphate anions effect on the nanodispersed titania synthesis during hydrolysis of titanium tetrachloride was studied. It was proposed that both chelating and bridging bidentate complexes formation between sulphate anions and octahedrally coordinated [Ti(OH)_h(OH₂)_6-h]^(4-h)+ mononers is the determinative factor for anatase phase nucleation.

Solution-phase synthesis of transition metal oxide nanocrystals: Morphologies, formulae, and mechanisms

In this review, we provide a broad overview of solution-phase synthesis of transition metal oxide nanocrystals (NCs), including a substantial catalog of published methods, and a unifying classification and discussion. Prevalent subcategories of solution-phase synthesis are delineated and general features are summarized. The diverse morphologies achievable by solution-phase synthesis are defined and exemplified. This is followed by sequential consideration of the solution-phase synthesis of first-row transition metal oxides. The common oxides of Ti, V, Mn, Fe, Co, Ni, Cu, and Zn are introduced; major crystal lattices are presented and illustrated; representative examples are explained; and numerous synthesis formulae are tabulated. Following this presentation of experimental studies, we present an introduction to theories of NC nucleation and growth. Various models of NC nucleation and growth are addressed, and important concepts determining the growth and structure of colloidal NCs are explained. Overall, this review provides an entry into systematic understanding of solution-phase synthesis of nanocrystals, with a reasonably comprehensive survey of results for the important category of transition metal oxide NCs.

Mixed-phase TiO2 photocatalysis: correlation between phase composition and photodecomposition of water pollutants

In most cases, the combination of both anatase (up to 80%) and rutile (up to 20%) structures in a mixed-phase TiO2 semiconductor results in a better photocatalytic performance compared to the pure phase. The improvement from anatase to rutile is brought about by the enhanced transportation of photogenerated electrons. This consequently results in improved efficiency of the photoelectric and photocurrent conversion. This review highlights the effects of the morphology, particle size, and crystal structure of mixed-phase TiO2 toward the photodegradation of water pollutants. It was demonstrated that the synergistic effect between anatase and rutile TiO2 due to the interfacial electron transfer from rutile to anatase improved the photocurrent as well as the overall conversion efficiency of the anatase photoanodes. The morphologies of mixed-phase TiO2 also contributed to the final photodegradation properties. The charge and electron transfer of mixed-phase TiO2 improved the 1D structure. This consequently enables photodegradation at the visible light range.

Electrosprayed TiO2 nanoporous hemispheres for enhanced electron transport and device performance of formamidinium based perovskite solar cells

Titanium dioxide (TiO₂) nanoporous hemispheres (NHSs) with a radius of ∼200 nm are fabricated by electrospraying a hydrothermally synthesized TiO₂ nanoparticle (NP) suspension solution. The resulting TiO₂ NHSs are highly porous, which are beneficial to the infiltration of perovskites and provide a larger contact area, as building blocks to construct a mesoporous TiO₂ layer for FA_0.81MA_0.15Pb(I_0.836Br_0.15)₃ based perovskite solar cells (PSCs). By varying the TiO₂ NHS collecting period (15 s, 30 s, 60 s and 90 s) during the electrospraying process, the performance of PSCs changes with different TiO₂ NHS distribution densities. The optimized PSC employing TiO₂ NHSs (60 s) exhibits a photovoltaic conversion efficiency (PCE) as high as 19.3% with a J_sc of 23.8 mA cm^-2, a V_oc of 1.14 V and a FF of 0.71. Furthermore, the PSC possesses a reproducible PCE value with little hysteresis in its current density-voltage (J-V) curves. The small perturbation transient photovoltage (TPV) measurement reveals a longer free carrier lifetime within the TiO₂ NHS based PSC than that in the TiO₂ NP based PSC, and the time of flight (TOF) photoconductivity measurement shows that charge mobilities in this system are also enhanced. These characteristics make TiO₂ NHSs a promising electron transport material for efficient photovoltaic devices.

Lewis acidity quantification and catalytic activity of Ti, Zr and Al-supported mesoporous silica

Water-tolerant metal supported Lewis acids were synthesized for the catalytic amidation of electron-poor and bulky amines.

The facile preparation of Ag decorated TiO2/ZnO nanotubes and their potent photocatalytic degradation efficiency

An illustration of the formation mechanism of Ag/TiO₂/ZnO nanotubes.

Electrospun tungsten trioxide nanofibers decorated with palladium oxide nanoparticles exhibiting enhanced photocatalytic activity

Tungsten trioxide (WO₃) based nanofibers have many advantages as photocatalysts due to its band gap which fits with readily accessible light sources.

Bio-mimicking TiO2 architectures for enhanced photocatalytic activity under UV and visible light

A multi-step chemical replication method using natural green leaves as templates can produce a porous, visible-light active TiO₂-based photocatalyst.

Catalytic Reforming of Oxygenates: State of the Art and Future Prospects

This Review describes recent advances in the design, synthesis, reactivity, selectivity, structural, and electronic properties of the catalysts for reforming of a variety of oxygenates (e.g., from simple monoalcohols to higher polyols, then to sugars, phenols, and finally complicated mixtures like bio-oil). A comprehensive exploration of the structure-activity relationship in catalytic reforming of oxygenates is carried out, assisted by state-of-the-art characterization techniques and computational tools. Critical emphasis has been given on the mechanisms of these heterogeneous-catalyzed reactions and especially on the nature of the active catalytic sites and reaction pathways. Similarities and differences (reaction mechanisms, design and synthesis of catalysts, as well as catalytic systems) in the reforming process of these oxygenates will also be discussed. A critical overview is then provided regarding the challenges and opportunities for research in this area with a focus on the roles that systems of heterogeneous catalysis, reaction engineering, and materials science can play in the near future. This Review aims to present insights into the intrinsic mechanism involved in catalytic reforming and provides guidance to the development of novel catalysts and processes for the efficient utilization of oxygenates for energy and environmental purposes.

Ease synthesis of mesoporous WO3-TiO2 nanocomposites with enhanced photocatalytic performance for photodegradation of herbicide imazapyr under visible light and UV illumination

Herein, we report the ease synthesis of mesoporous WO3-TiO2 nanocomposites at different WO3 contents (0-5wt%) together with their photocatalytic performance for the degradation of the imazapyr herbicide under visible light and UV illumination. XRD and Raman spectra indicated that the highly crystalline anatase TiO2 phase and monoclinic and triclinic of WO3 were formed. The mesoporous TiO2 exhibits large pore volumes of 0.267cm(3)g-1 and high surface areas of 180m(2)g(-1) but they become reduced to 0.221cm(3)g(-1) and 113m(2)g(-1), respectively upon WO3 incorporation, with tunable mesopore diameter in the range of 5-6.5nm. TEM images show WO3-TiO2 nanocomposites are quite uniform with 10-15nm of TiO2 and 5-10nm of WO3 sizes. Under UV illumination, the overall photocatalytic efficiency of the 3% WO3-TiO2 nanocomposite is 3.5 and 6.6 times higher than that of mesoporous TiO2 and commercial UV-100 photocatalyst, respectively. The 3% WO3-TiO2 nanocomposite is considered to be the optimum photocatalyst which is able to degrade completely (100% conversion) of imazapyr herbicide along 120min with high photonic efficiency ∼8%. While under visible light illumination, the 0.5% WO3-TiO2 nanocomposite is the optimum photocatalyst which achieves 46% photocatalytic efficiency.

Strong pyro-catalysis of pyroelectric BiFeO3 nanoparticles under a room-temperature cold-hot alternation

A strong pyro-catalytic dye degradation with an ultrahigh degradation efficiency (>99%) in hydrothermally synthesized pyroelectric BiFeO3 nanoparticles was achieved under a room-temperature cold-hot alternating excitation (between 27 °C to 38 °C). The pyro-catalysis originated from a combination of the pyroelectric effect and the electrochemical oxidation-reduction reaction. The intermediate products (hydroxyl radicals and superoxide radicals) of pyro-electro-catalysis were observed. Pyro-catalysis provides a highly efficient and reusable dye wastewater decomposition technology through utilizing environmental day-night temperature variation.

A novel triphenylamine-based dye sensitizer supported on titania nanoparticles and the effect of titania fabrication on its optical properties

A new synthesised triphenylamine-based dye having a branched structure with one OH-ending branch able to interact with the surface hydroxyl moieties of mesoporous TiO

Fabrication of TiO2–graphene composite for the enhanced performance of lithium batteries

The controllable synthesis of TiO₂ nanostructures with a conformal and ultrathin graphitic carbon coating is critically desirable for new anode material development for Li-ion batteries.