Defective TiO2 with oxygen vacancies: synthesis, properties and photocatalytic applications

Synergistic formation of sulfate and ammonium resulting from reaction between SO2 and NH3 on typical mineral dust

A synergistic effect between SO₂ and NH₃ on typical mineral dust.

Single oxygen vacancies of (TiO2)35 as a prototype reduced nanoparticle: implication for photocatalytic activity

The properties of single oxygen vacancies of (TiO₂)₃₅, a prototype of an anatase nanoparticle, were investigated by DFT calculations.

High-performance lithium storage of Ti3+-doped anatase TiO2@C composite spheres

Ti³⁺-Doped anatase TiO₂@C composite spheres as the anode materials for lithium ion batteries.

Optimized design of multi-shell ZnO/TiO2/ZnSe nanowires decorated with Ag nanoparticles for photocatalytic applications

The photocatalytic activity of ZnO/TiO₂/Ag/ZnSe nanowires was significantly enhanced under light irradiation compared with that of ZnO/TiO₂/ZnSe/Ag nanowires.

Surface defect engineering: gigantic enhancement in the optical and gas detection ability of metal oxide sensor

By using surface defect engineering, the gigantic enhancement in UV and gas detection abilities of nanosensors can be achieved.

Simple synthesis of lithium-doped sulfated titania nanoparticles and their high visible light photocatalytic activity under negative bias electrostatic field

Li-doped TiO₂/SO₄²⁻ nanoparticles were successfully synthesized via a simple calcinination process in a vacuum environment using Ti(SO₄)₂ and LiBr as precursors, and were characterised by TEM, XRD, IR, DLS, XPS and UV-vis (DRS).

A versatile sol–gel coating for mixed oxides on nanoporous gold and their application in the water gas shift reaction

Ceria–titania mixed oxides on a structured nanoporous gold support result in highly active and durable catalysts for the water-gas shift reaction.

Rutile titanium dioxide prepared by hydrogen reduction of Degussa P25 for highly efficient photocatalytic hydrogen evolution

The quantum efficiency of reduced TiO₂ was 46% under 390 nm irradiation, which was much higher than that of Degussa P25.

Oxygen vacancy induced Bi2WO6 for the realization of photocatalytic CO2 reduction over the full solar spectrum: from the UV to the NIR region

Bi₂WO₆ with oxygen vacancies was demonstrated as an efficient photocatalyst for CO₂ reduction into energy-rich CH₄ over the UV-Vis-NIR full spectrum.

A synergetic effect of surface plasmon and ammoniation on enhancing photocatalytic activity of ZnO nanorods

A synergetic effect of surface plasmon (SP) and ammoniation on the enhancements of both ultraviolet and visible photocatalytic activities of ZnO nanorods is reported.

An oxygen-vacancy rich 3D novel hierarchical MoS2/BiOI/AgI ternary nanocomposite: enhanced photocatalytic activity through photogenerated electron shuttling in a Z-scheme manner

Herein, we propose the photocatalytic mechanism, involving a Z-scheme and oxygen vacancy states, for the MoS₂/BiOI/AgI nanocomposite.

The promotional effect of surface defects on the catalytic performance of supported nickel-based catalysts

Supported nickel-based catalysts derived from layered double hydroxides exhibited superior catalytic hydrogenation performance due to the promotional effect of surface defects.

Enabling higher photoelectrochemical efficiency of TiO2via controlled formation of a disordered shell: an alternative to the hydrogenation process

A simple one-step and low-temperature process was developed to form an amorphous overlayer on the crystalline TiO₂film by atomic layer deposition.

Three-dimensional ruthenium-doped TiO2 sea urchins for enhanced visible-light-responsive H2 production

Ru-doped rutile TiO₂ composed of radially aligned nanorods exhibits good H₂ production from water under visible light irradiation.

Designed Synthesis of In₂O₃ Beads@TiO₂-In₂O₃ Composite Nanofibers for High Performance NO₂ Sensor at Room Temperature

Porous single crystal In2O3 beads@TiO2-In2O3 composite nanofibers (TINFs) have been prepared via a facile electrospinning method. The beads were formed because of the existence of hemimicelles in pecursor solution. The formation of hemimicelles was attributed to the synergy of tetrabutyl titanate (TBT) and polyvinylpyrrolidone (PVP). Abundant In(3+) ions were drawn toward the ketonic oxygen of PVP resulting in In(3+) ions aggregation. Compared with pristine In2O3 nanofibers (INFs), the as-prepared TINFs exhibited excellent properties for sensing NO2 gas at room temperature (25 °C). The enhanced sensing property was due to much absorbed oxygen and Schottky junctions between the porous single crystal In2O3 beads and the Au electrode of the sensor. The strategy for combining the unique In2O3 beads@TiO2-In2O3 nanofibers structure which possessed superior conductivity and sufficient electrons with the addition of TiO2 offered an innovation to enhance the gas sensing performance.

Hydrogenated TiO2 nanobelts as highly efficient photocatalytic organic dye degradation and hydrogen evolution photocatalyst

TiO2 nanobelts have gained increasing interest because of its outstanding properties and promising applications in a wide range of fields. Here we report the facile synthesis of hydrogenated TiO2 (H-TiO2) nanobelts, which exhibit excellent UV and visible photocatalytic decomposing of methyl orange (MO) and water splitting for hydrogen production. The improved photocatalytic property can be attributed to the Ti(3+) ions and oxygen vacancies in TiO2 nanobelts created by hydrogenation. Ti(3+) ions and oxygen vacancies can enhance visible light absorption, promote charge carrier trapping, and hinder the photogenerated electron-hole recombination. This work offers a simple strategy for the fabrication of a wide solar spectrum of active photocatalysts, which possesses significant potential for more efficient photodegradation, photocatalytic water splitting, and enhanced solar cells using sunlight as light source.

Defective ZnFe₂O₄ nanorods with oxygen vacancy for photoelectrochemical water splitting

A one-dimensional zinc ferrite (ZnFe2O4) nanorod photoanode was prepared by a simple solution method on the F-doped tin oxide glass substrate. Thermal treatment under a hydrogen or vacuum atmosphere improved the photoelectrochemical water oxidation activity up to 20 times. The various physical characterization techniques used revealed that oxygen vacancies were created by the treatments in the near surface region, which increased the donor density and passivated the surface states. Hydrogen treatment was more effective and it was important to find optimum treatment conditions to take advantage of the positive role of oxygen vacancy as a source of electron donors and avoid its negative effect as electron trap sites.

Enabling high solubility of ZnO in TiO₂ by nanolamination of atomic layer deposition

Zn-doped TiO2 nanotubes were fabricated by nanolaminated packing of alternating layers of TiO2 and ZnO by atomic layer deposition (ALD) using a polycarbonate (PC) membrane as a template. With 400 cycles of ALD, the nanotubes with a thickness of 28 nm and an outer diameter of 220 nm were obtained after removing the PC membrane by annealing at 450 °C. The doping concentration of ZnO in TiO2 depends on the precursor cycle ratio of ZnO to TiO2. With the precursor cycle ratio of ZnO : TiO2 at 0.04, a uniform bulk solubility of ∼8 at% is obtained, and the surface concentration of Zn is even higher, ∼16 at%. From the depth profiles measured by secondary ion mass spectrometry, Zn is uniformly distributed across the thickness, which is further confirmed by analyses of X-ray photoelectron spectroscopy, X-ray diffraction, and Raman spectroscopy. Additionally, from the transmission electron microscopic observation, the highly doped anatase TiO2 exhibits some regions of severe deformation that results in localized solid-state amorphization.

A visualized probe method for localization of surface oxygen vacancy on TiO2: Au in situ reduction

Surface oxygen vacancy has been investigated extensively due to its great influence on photocatalysis in recent years. Among these investigations, the location of surface defects is found to be a key factor during the photocatalytic procedure. Especially when a crystal facet is involved, the synergistic action between these two factors may greatly increase the photocatalytic efficiency. Location of defects would greatly help in understanding the mechanism of this coupling action. Without an available technique, however, it is very difficult to gain the position information directly. In this paper, we provide a low-cost and visualized method to solve this problem via in situ reduction of Au. TiO2 with surface oxygen vacancy on a specific area is synthesized via a photochemical reaction. Then the Au ion was reduced at the place where oxygen vacancy exists on the TiO2 surface. Hence, the localization of surface vacancy will be determined by examining the location of Au particles. Moreover, application of this method can be extended to other surface defects such as oxygen vacancy on oxide semiconductors, Ti(3+) in TiO2, Zn vacancy on ZnO, etc. This technique is helpful for understanding how surface defects affect the properties of semiconductors.

A Biomineralization Strategy for "Net"-Like Interconnected TiO2 Nanoparticles Conformably Covering Reduced Graphene Oxide with Reversible Interfacial Lithium Storage

A green and simple biomineralization-inspired method to create "net"-like interconnected TiO₂ nanoparticles conformably covering reduced graphene oxide (RGO) with high loading density is reported. This method uses polyamine as both the biomineralization agent and linker to manipulate the nucleation, growth, and crystallization of TiO₂ nanoparticles on the surface of graphene oxide. The obtained TiO₂/RGO composites demonstrate sub-10-nm TiO₂ nanoparticles with (001) facets, ultrathin thickness (10-12 nm), and a high surface area of 172 m² g^-1. When used as anode material for lithium ion batteries, the material displayed excellent rate capability and long cycle life; a capacity of 155 mAh g^-1 is obtained after 50 cycles at the rate of 5C (1C = 168 mA g^-1) and a specific capacity of 115 mAh g^-1 is retained after 2000 cycles at the rate of 25C, which is much higher than that of mechanically mixed TiO₂/graphene composites. Detailed discharge curve analysis reveals that the high rate and cycle performance are partly a result of the reversible interfacial lithium storage of materials, which might be attributed to the pores in the TiO₂ nets on the RGO and may provide a sufficient number of interfaces for accepting both electrons and lithium ions.

Structure and Formation Mechanism of Black TiO2 Nanoparticles

The remarkable properties of black TiO2 are due to its disordered surface shell surrounding a crystalline core. However, the chemical composition and the atomic and electronic structure of the disordered shell and its relationship to the core remain poorly understood. Using advanced transmission electron microscopy methods, we show that the outermost layer of black TiO2 nanoparticles consists of a disordered Ti2O3 shell. The measurements show a transition region that connects the disordered Ti2O3 shell to the perfect rutile core consisting first of four to five monolayers of defective rutile, containing clearly visible Ti interstitial atoms, followed by an ordered reconstruction layer of Ti interstitial atoms. Our data suggest that this reconstructed layer presents a template on which the disordered Ti2O3 layers form by interstitial diffusion of Ti ions. In contrast to recent reports that attribute TiO2 band-gap narrowing to the synergistic action of oxygen vacancies and surface disorder of nonspecific origin, our results point to Ti2O3, which is a narrow-band-gap semiconductor. As a stoichiometric compound of the lower oxidation state Ti(3+) it is expected to be a more robust atomic structure than oxygen-deficient TiO2 for preserving and stabilizing Ti(3+) surface species that are the key to the enhanced photocatalytic activity of black TiO2.

Defective titanium dioxide single crystals exposed by high-energy {001} facets for efficient oxygen reduction

The cathodic material plays an essential role in oxygen reduction reaction for energy conversion and storage systems. Titanium dioxide, as a semiconductor material, is usually not recognized as an efficient oxygen reduction electrocatalyst owning to its low conductivity and poor reactivity. Here we demonstrate that nano-structured titanium dioxide, self-doped by oxygen vacancies and selectively exposed with the high-energy {001} facets, exhibits a surprisingly competitive oxygen reduction activity, excellent durability and superior tolerance to methanol. Combining the electrochemical tests with density-functional calculations, we elucidate the defect-centred oxygen reduction reaction mechanism for the superiority of the reductive {001}-TiO_2−x nanocrystals. Our findings may provide an opportunity to develop a simple, efficient, cost-effective and promising catalyst for oxygen reduction reaction in energy conversion and storage technologies.

Titanium dioxide is not generally considered to be an effective oxygen reduction catalyst. Here, the authors show that nanostructured titanium dioxide, self-doped with oxygen vacancies and with exposed high-energy {001} facets, exhibits competitive oxygen reduction catalytic activity and durability.

Highly photocatalytic TiO2 interconnected porous powder fabricated by sponge-templated atomic layer deposition

A titanium dioxide (TiO2) interconnected porous structure has been fabricated by means of atomic layer deposition of TiO2 onto a reticular sponge template. The obtained freestanding TiO2 with large surface area can be easily taken out of the water to solve a complex separation procedure. A compact and conformal nanocoating was evidenced by morphologic characterization. A phase transition, as well as production of oxygen vacancies with increasing annealing temperature, was detected by x-ray diffraction and x-ray photoelectron spectroscopy, respectively. The photocatalytic experimental results demonstrated that the powder with appropriate annealing treatment possessed excellent photocatalytic ability due to the co-action of high surface area, oxygen vacancies and the optimal crystal structure.

Sonophotodeposition of bimetallic photocatalysts Pd-Au/TiO2 : application to selective oxidation of methanol to methyl formate

The aim of this work is to develop bimetallic Pd-Au/TiO2 P90 systems, which are highly active and selective for the photocatalytic oxidation of methanol to form methyl formate. Modification of commercial TiO2 P90 with Pd-Au nanoparticles was successfully achieved for the first time by means of a sonophotodeposition (SPD) method. The prepared materials were characterized by TEM, UV/Vis spectroscopy, X-ray photoelectron spectroscopy, and powder XRD. The Pd-Au bimetallic nanoparticles supported on titania exhibited remarkably enhanced catalytic activity in selective methanol oxidation to form methyl formate due to the synergism of Au and Pd particles, as well as the strong interaction between TiO2 and Pd-Au. SPD is a green methodology that can be used to prepare well-defined bimetallic surfaces on semiconductor supports with great promise for catalytic applications, in which selectivity can be tuned through adjustment of the surface composition.

One-dimensional hybrid nanostructures for heterogeneous photocatalysis and photoelectrocatalysis

Semiconductor-based photocatalysis and photoelectrocatalysis have received considerable attention as alternative approaches for solar energy harvesting and storage. The photocatalytic or photoelectrocatalytic performance of a semiconductor is closely related to the design of the semiconductor at the nanoscale. Among various nanostructures, one-dimensional (1D) nanostructured photocatalysts and photoelectrodes have attracted increasing interest owing to their unique optical, structural, and electronic advantages. In this article, a comprehensive review of the current research efforts towards the development of 1D semiconductor nanomaterials for heterogeneous photocatalysis and photoelectrocatalysis is provided and, in particular, a discussion of how to overcome the challenges for achieving full potential of 1D nanostructures is presented. It is anticipated that this review will afford enriched information on the rational exploration of the structural and electronic properties of 1D semiconductor nanostructures for achieving more efficient 1D nanostructure-based photocatalysts and photoelectrodes for high-efficiency solar energy conversion.

Leucas aspera mediated multifunctional CeO2 nanoparticles: Structural, photoluminescent, photocatalytic and antibacterial properties

Spherical shaped cerium dioxide (CeO2) nanoparticles (NPs) were synthesized via bio mediated route using Leucas aspera (LA) leaf extract. The NPs were characterized by PXRD, SEM, UV-Visible techniques. Photoluminescence (PL), photocatalysis and antibacterial properties of NPs were studied. PXRD patterns and Rietveld analysis confirm cubic fluorite structure with space group Fm-3m. SEM results evident that morphology of the NPs was greatly influenced by the concentration of LA leaf extract in the reaction mixture. The band gap energy of the NPs was found to be in the range of 2.98-3.4 eV. The photocatalytic activity of NPs was evaluated by decolorization of Rhodamine-B (RhB) under UVA and Sun light irradiation. CeO2 NPs show intense blue emission with CIE coordinates (0.14, 0.22) and average color coordinated temperature value ∼148,953 K. Therefore the present NPs quite useful for cool LEDs. The superior photocatalytic activity was observed for CeO2 NPs with 20 ml LA under both UVA and Sunlight irradiation. The enhanced photocatalytic activity and photoluminescent properties were attributed to defect induced band gap engineered CeO2 NPs. Further, CeO2 with 20 ml LA exhibit significant antibacterial activity against Escherichia coli (EC) and Staphylococcus aureus (SA). These findings show great promise of CeO2 NPs as multifunctional material for various applications.

Ionic liquid self-combustion synthesis of BiOBr/Bi24O31Br10 heterojunctions with exceptional visible-light photocatalytic performances

Heterostructured BiOBr/Bi24O31Br10 nanocomposites with surface oxygen vacancies are constructed by a facile in situ route of one-step self-combustion of ionic liquids. The compositions can be easily controlled by simply adjusting the fuel ratio of urea and 2-bromoethylamine hydrobromide (BTH). BTH serves not only as a fuel, but also as a complexing agent for ionic liquids and a reactant to supply the Br element. The heterojunctions show remarkable adsorptive ability for both the cationic dye of rhodamine B (RhB) and the anionic dye of methylene orange (MO) at high concentrations, which is attributed to the abundant surface oxygen vacancies. The sample containing 75.2% BiOBr and 24.8% Bi24O31Br10 exhibits the highest photocatalytic activity. Its reaction rate constant is 4.0 and 9.0 times that of pure BiOBr in degrading 50 mg L(-1) of RhB and 30 mg L(-1) of MO under visible-light (λ > 400 nm) irradiation, respectively, which is attributed to the narrow band gap and highly efficient transfer efficiency of charge carriers. Different photocatalytic reaction processes and mechanisms over pure BiOBr and heterojunctions are proposed.

Synthesis and Characterization of CeO2 Nanoparticles via Solution Combustion Method for Photocatalytic and Antibacterial Activity Studies

CeO₂ nanoparticles have been proven to be competent photocatalysts for environmental applications because of their strong redox ability, nontoxicity, long-term stability, and low cost. We have synthesized CeO₂ nanoparticles via solution combustion method using ceric ammonium nitrate as an oxidizer and ethylenediaminetetraacetic acid (EDTA) as fuel at 450 °C. These nanoparticles exhibit good photocatalytic degradation and antibacterial activity. The obtained product was characterized by various techniques. X-ray diffraction data confirms a cerianite structure: a cubic phase CeO₂ having crystallite size of 35 nm. The infrared spectrum shows a strong band below 700 cm⁻¹ due to the Ce−O−Ce stretching vibrations. The UV/Vis spectrum shows maximum absorption at 302 nm. The photoluminescence spectrum shows characteristic peaks of CeO₂ nanoparticles. Scanning electron microscopy (SEM) images clearly show the presence of a porous network with a lot of voids. From transmission electron microscopy (TEM) images, it is clear that the particles are almost spherical, and the average size of the nanoparticles is found to be 42 nm. CeO₂ nanoparticles exhibit photocatalytic activity against trypan blue at pH 10 in UV light, and the reaction follows pseudo first-order kinetics. Finally, CeO₂ nanoparticles also reduce Cr^VI to Cr^III and show antibacterial activity against Pseudomonas aeruginosa.

Gold nanoparticles-sensitized wide and narrow band gap TiO2 for visible light applications: a comparative study

Photocatalytic degradation of dyes and organic compounds by Au/P-TiO₂ and Au/M-TiO₂ nanocomposites under visible light irradiation.

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.

Vacuum heat treated titanate nanotubes for visible-light photocatalysis

Visible light-active TiO₂(B)/anatase heterojunction nanotubes are prepared, which show better visible light photocatalytic activity than commercial Degussa P25.

Mechanism of hydrogen treatment in KTiOPO4 crystals at high temperature: experimental and first-principles studies

The mechanism of coloration and oxygen vacancy formation in KTP crystals treated by hydrogen annealing was systematically investigated.

Structural heterogeneity and dynamics of dyes on TiO2: implications for charge transfer across organic–inorganic interfaces

Structural heterogeneity, solvation, and thermal fluctuations all contribute to multiple dye–semiconductor charge injection rates.