Co-doped Anatase TiO2 Research Articles

Soft synthesis of Bi Doped and Bi–N co-doped TiO2 nanocomposites: A comprehensive mechanistic approach towards visible light induced ultra-fast photocatalytic degradation of fabric dye pollutant

The present work reports on the soft precipitation synthesis of Bi doped and Bi–N co-doped anatase TiO2 nanoparticles that exhibit superior photocatalytic activity under visible light illumination. The photo-oxidative properties of the doped and co-doped TiO2 nanoparticles have been evaluated with Acid Red 85—a fabric azo dye. The influence of physio-chemical parameters such as, solution pH, dopant stoichiometry, dye concentration, catalyst quantity, electron acceptors, illumination time and light intensity, has been investigated to study the extent of dye photocatalytic degradation. The modified TiO2 particles are found to exhibit faster degradation time (≤0.33h for Bi–TiO2 and ≤0.16h for Bi–N–TiO2), using 20g/L of the photocatalyst materials. The photocatalysts are characterized using, XRD, SEM, TEM, EDAX, SAED, XPS, UV–vis-DRS, PLS, TGA, and BET analysis. The band gap measurements for the TiO2, Bi–TiO2 and Bi–N–TiO2 particles reveal values of 3.15, 3.01 and 2.88eV, respectively. The synergetic combination of Bi and N co-doping plays a significant role in the narrowing the band gap energy of the photocatalysts, thereby resulting in superior visible light photocatalytic activity.

Characterization and photocatalytic performance of La and C co-doped anatase TiO2 for photocatalytic reduction of Cr(VI)

Abstract The La and C co-doped anatase TiO 2 nano-materials were synthesized by a hydrothermal method. The structures of La and C co-doped TiO 2 were characterized by XRD, FT-IR, XPS, DRS, SEM and nitrogen adsorption–desorption isotherms. The results indicated that pH values have a greater effect on the crystalline phase, crystal size and crystallinity degree of TiO 2 . The La and C co-doping could inhibit the phase transformation and crystallite growth of TiO 2 . The photocatalytic activities of La and C co-doped TiO 2 for photocatalytic reduction of Cr(VI) under visible light irradiation using different La contents were also studied. The La and C co-doped TiO 2 nano-materials with La:Ti weight ratio of 0.3 exhibits the highest photocatalytic activity for Cr(VI) photocatalytic reduction under visible light irradiation, which can be attributed to the synergic effect of the higher BET surface area, surface hydroxyl content and optimum La contents.

Electronic structure of (Cu+N) co-doped anatase TiO<sub>2</sub> at the surfaces of (001) and (101): A first-principle study

采用基于密度泛函理论的第一性原理方法研究了3d过渡元素Cu掺杂及(Cu+N)共掺杂于锐钛矿相TiO 2 (001)面和(101)面的电子性质, 给出了不同掺杂形式形成能、能带结构、态密度及电荷分布的变化, 得出了(Cu+N)共掺杂时最稳定的结构. 通过计算Cu表层吸附、表层和次表层替位掺杂以及晶体间隙掺杂的形成能, 发现Cu掺杂更易发生在TiO 2 (001)面的空穴位, 此时N偏向于在水平方向上的O位发生替位掺杂. 计算结果表明(Cu+N)共掺杂后Cu-3d与O-2p, N-2p及Ti-3d轨道上的电子发生p-d杂化效应, 引发O-2p, N-2p态发生劈裂使得价带范围扩大, Ti-3d态下移且发生劈裂形成新的导带底, 并且禁带中产生了新的电子态, 禁带宽度减小, 同时(Cu+N)施主受主杂质对的出现可以有效防止电子空穴对的复合, 提高了TiO 2 的光催化活性.

Fe, S co-doped anatase TiO2nanotubes as anodes with improved electrochemical performance for lithium ion batteries

Fe, S co-doped TiO2nanotubes are synthesized by a sol–gel and subsequent chemical process, exhibiting improved electrochemical performance for LIBs.

Ce/S共掺杂锐钛矿型TiO2的第一性原理研究

Ce/S共掺杂锐钛矿型TiO₂的第一性原理研究

Electronic and Magnetic Properties Studies on Mn and Oxygen Vacancies Codoped Anatase TiO2

The electronic and magnetic properties of Mn and oxygen vacancies codoped anatase TiO2were investigated. The calculated results showed that the TiO2codoped with Mn and oxygen vacancies have a magnetic moment value of 3.415 μBper Ti31MnO63supercell. Furthermore, Ti31MnO63gets the lowest energy with a geometrical optimization where the Mn ions locate at the nearest-neighbor sites of the oxygen vacancy. And experimental results indicated the magnetism is associated with the defects of Mn ions and oxygen vacancies induced by the Mn doping, which is consistent with the calculation results.

Band gap and morphology engineering of TiO2 by silica and fluorine co-doping for efficient ultraviolet and visible photocatalysis

Silicon and fluorine co-doped anatase TiO2 (Si–F–TiO2) photocatalysts with enhanced photocatalytic activity were successfully prepared via a facile two-step synthetic method by using SiO2 powders and (NH4)2TiF6 as the precursors.

Ti<sub>1-2x</sub>Al<sub>x</sub>Nb<sub>x</sub>O<sub>2</sub>陶瓷介电性质的研究

本文通过传统的固相烧结法制备了一系列(Al+NB)共掺杂锐钛矿TiO2陶瓷，浓度分别为0.5%, 1%, 2% 和5%，摸索出了拥有优异介电性能的掺杂TiO2陶瓷最佳制备条件：掺杂量x = 0.02时，在1500℃温度下空气气氛中烧结10 h。通过对样品的微观结构、元素以及价态分析、介电温度谱等方面的研究，实验发现Ti1-2xAlxNbxO2陶瓷由锐钛矿型结构转变为金红石相结构；具有很高的致密性；陶瓷的介电性能有很好的频率稳定性以及温度稳定性；表面势垒层电容效应与晶界效应引起的界面极化效应均不是引起巨介电的主要原因，优异介电性能的主要因素来自于电子钉扎缺陷偶极子效应。 In this work, the (Al + Nb) co-doped anatase TiO2 ceramics were prepared by conventional solid phase sintering, and the concentrations were 0.5%, 1%, 2% and 5%, respectively. The optimized annealing conditions for (Al + Nb) co-doped TiO2 ceramics were 1500˚C for 10 h under air atmosphere and the concentration was 2%. According to the sample’s analysis of the microstructure, element, valence, different temperature of dielectric properties, we find that the structure of ceramics transforms from anatase phase structure into rutile phase structure, and all the ceramics have very high density. Their dielectric properties have a very good frequency and temperature stability. The primary origin of the observed colossal dielectric permittivities apparent in our ceramics is not fundamentally related to surface barrier layer capacitor (SBLC) effect and grain boundary effect. Electron-pinned defect-dipoles effect is responsible for the excellent CP properties observed in (Al + Nb) co-doped TiO2.

Tailoring the electronic and optical properties of anatase TiO2 by (S, Nb) co-doping from a DFT plus U calculation

Abstract The geometrical structure, defect formation, electronic and optical properties of S-doped, Nb-doped, and (S, Nb)-codoped anatase TiO 2 were successfully calculated by the first-principles plane-wave ultrasoft pseudopotential method based on the density functional theory with plus U method. Firstly, the geometrical structure demonstrates that the (S, Nb) co-doping can effectively induce lattice distortion and reduce the recombination of electron–hole pairs. Note that the (S, Nb)-codoped system further reduces the band gap compared with pure and mono-doped TiO 2 due to the mixture of S 2p and Nb 4d states appears in the gap, which results in an obvious red-shift in the optical absorption spectra and improves the photocatalytic activity. Moreover, the (S, Nb) co-doping should be grown under Ti-rich conditions while S or Nb mono-doping is expected to be easier under O-rich conditions. The above results would be beneficial to further developing for titanium dioxide photocatalyst.

First-principles study of atomic structure and electronic properties of Si and F doped anatase TiO2

Abstract Chemical doping represents one of the most effective ways in engineering electronic structures of anatase TiO2 for practical applications. Here, we investigate formation energies, geometrical structures, and electronic properties of Si-, F-doped and Si/F co-doped anatase TiO2 by using spin-polarized density functional theory calculation. We find that the co-doped TiO2 is thermodynamically more favorable than the Si- and F-doped TiO2- Structural analysis shows that atomic impurity varies crystal constants slightly. Moreover, all the three doped systems show a pronounced narrowing of band gap by 0.33 eV for the F-doped TiO2, 0.17 eV for the Si-doped TiO2, and 0.28 eV for the Si/F-co-doped TiO2, which could account for the experimentally observed redshift of optical absorption edge. Our calculations suggest that the Si/F-co-doping represents an effective way in tailoring electronic structure and optical properties of anatase TiO2.

Visible-light photocatalytic properties of Mo–C codoped anatase TiO2 films prepared by magnetron sputtering

A range of different contents of Mo–C codoped TiO2 films were sputtered by using home-made Mo–C codoped TiO2 targets, which were sintered by mixing the Mo2C and TiO2 powder with different mole ratio. We found that the Mo and C ions were successfully incorporated into the lattice of TiO2 films. As a result, the band gap of TiO2 was reduced and the visible-light photocatalytic property was enhanced. The photocatalytic performance of Mo–C codoped TiO2 films was strictly relevant with the band gap and there was a best codoping concentration of 0.01% for the TiO2 film, which processed the smallest band gap and the best photocatalytic property. If the codoping concentration increased, the photocatalytic performance decreased dramatically. Our results suggest that sputtering technique is a convenient method to prepare Mo–C codoped TiO2 films with tunable doping content and high photocatalytic performance.

Electronic structure of Gd/N co-doped anatase TiO2 by first-principles calculations

The lattice parameters, energy band structures, density of states, and optical absorption spectra of Gd-doped, N-doped, and Gd/N co-doped anatase TiO2 were calculated by the first-principles based on the density functional theory. The calculated results indicate that the three kinds of doping all induce lattice distortion for TiO2, but the structures still keep unchanged. Gd doping introduces an empty energy band in the forbidden band of TiO2, and N doping introduces an impurity energy level above the maximum valence band. Gd/N co-doping forms an impurity energy level and a full-filled energy band in the forbidden band of TiO2, where the impurity energy level lies above the full-filled energy band. The experimental results for the photocatalytic activity enhancement of TiO2 by the Gd/N co-doping can be explained perfectly from the calculation results.

Impact of Oxygen Vacancy on Band Structure Engineering of n-p Codoped Anatase TiO2

Doping with various impurities is an effective approach to improve the photoelectrochemical properties of TiO2. Here, we explore the effect of oxygen vacancy on geometric and electronic properties of compensated (i.e. V-N and Cr-C) and non-compensated (i.e. V-C and Cr-N) codoped anatase TiO2 by performing extensive density functional theory calculations. Theoretical results show that oxygen vacancy prefers to the neighboring site of metal dopant (i.e. V or Cr atom). After introduction of oxygen vacancy, the unoccupied impurity bands located within band gap of these codoped TiO2 will be filled with electrons, and the position of conduction band offset does not change obviously, which result in the reduction of photoinduced carrier recombination and the good performance for hydrogen production via water splitting. Moreover, we find that oxygen vacancy is easily introduced in V-N codoped TiO2 under O-poor condition. These theoretical insights are helpful for designing codoped TiO2 with high photoelectrochemical performance.

Properties and photochemistry of valence-induced-Ti(3+) enriched (Nb,N)-codoped anatase TiO2 semiconductors.

Nb and N codoped TiO2s are outstandingly versatile semiconductor oxides. Their high conductivity makes them valid alternatives to commercially available, but very expensive, conductive oxides. They show increased photonic efficiencies compared to the cases of solely Nb or N doped TiO2, when used as visible light sensitised photocatalysts. Furthermore, they are excellent materials for O2 sensors at very low temperature. Despite these remarkable properties, a clear picture of the electronic and optical mechanisms induced by the simultaneous presence of the dopants has just begun to be understood. Using a combination of electron paramagnetic resonance (EPR) spectroscopy, electrochemical impedance spectroscopy (EIS) and optical spectroscopy, we present here novel fundamental insights into the mechanisms responsible for the enhanced conductivity and visible light photochemistry.

First-principles study of N/Cu co-doped anatase TiO2

Using the first-principles plane-wave ultra-soft pseudo-potential method based on the density functional theory, the structures, electronic-structures and optical properties of pure anatase TiO2, N (Cu) doped TiO2, and N/Cu co-doped TiO2 crystal are studied by the local-spin density approximation plus Hubbard U method. It is shown that the lattice constants become larger because of the lattice distortion caused by doping. Impurity levels in the band gap of TiO2 are introduced by N and Cu doping, and the forbidden band width is correspondingly changed. For N doped TiO2, the reduction of the band gap is weak, while the N/Cu co-doped TiO2 band gap decreases remarkably. It leads to a red shift of visible absorption spectrum and enhances optical catalysis. The effect is useful for the practical application of photo-catalytic.

Theoretical and experimental studies on N, Fe, La co-doped anatase TiO2 band adjustment

Based on the plane wave method (PWPP) of densiy functional theory (DFT) we model the N, Fe, La three elements co-doped anatase TiO2 crystal structure and calculate its band structure and density of states with Material Studio. By the sol-gel method, the intrinsic anatase TiO2 and the anatase TiO2 with N, Fe, La three elements co-doping are prepared and investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Results indicate that the changes of the N, Fe, La co-doped TiO2 lattice volume and its bond length will result in a decline of the crystal symmetry and the effective separation of the electron-hole pair. Impurity level appearing at the bottom of the conduction band and at the top of valence band leads to the decrease of the TiO2 forbidden band width(1.78 eV to 1.35 eV, reduced by 25%), the red shift of light absorption edge, the increase of density of states as well as, the improve ment of electron transition probability and the photocatalytic efficiency of TiO2. Ion doping makes the particles in doped TiO2 become smaller, i.e. the size of particles in TiO2>N/Fe_TiO2>N/Fe/La_TiO2, the emission peak of the N/Fe/La: TiO2 is 425 nm and its energy gap is smaller than that of the intrinsic TiO2. The measured N/Fe/La: TiO2 photocatalytic ability is stronger than the N/Fe: TiO2, the origin can be due to the increasing number of the electronic states and the impurity energy levels.

N and Ti3+ co-doped 3D anatase TiO2 superstructures composed of ultrathin nanosheets with enhanced visible light photocatalytic activity

A novel 3D-hierarchical anatase co-doped with N and Ti3+ was synthesized via a facile template-free solvothermal method for improved vis-photocatalytic activity.

A facile solution approach to W,N co-doped TiO2 nanobelt thin films with high photocatalytic activity

W,N co-doped anatase TiO2 nanobelt films were synthesized by direct oxidation of metallic Ti substrates with H2O2 solutions containing H2WO4 and C3H6N6 at 80 °C, followed by a subsequent calcination. The photocatalytic activity of the W,N co-doped anatase TiO2 nanobelt films was nearly three times that of undoped alkali-hydrothermal synthesized anatase TiO2 nanobelt films, under UV and visible light illumination.

First-principles study on the synergistic effects of codoped anatase TiO2 photocatalysts codoped with N/V or C/Cr

An effective compensated codoping approach is described to modify the photoelectrochemical properties of anatase TiO2 by doping with nonmetals (N or C) and transition metals (V or Cr) impurities. Here, compensated codoped TiO2 systems are constructed with different dopant species and sources, and then their dopant formation energies and electronic structures are performed to study the stability and visible-light photoactivity by first-principles plane-wave ultrasoft pseudopotential calculations, respectively. The calculated results demonstrate that the codoping with transition metals facilitates the enhancement of the concentration of p-type dopants (N and C) in a host lattice. Especially, compensated codoping not only reduces the energy gap, to enhance the optical absorption, and eliminate the local trapping, to improve carrier mobility and conversion efficiency, but it also keeps the oxidation-reduction potential of the conduction band edge. These results are conducive to the understanding of the synergistic mechanism of the photocatalytic activity of TiO2 that is enhanced by codoping.

Bamboo leaf-assisted formation of carbon/nitrogen co-doped anatase TiO2 modified with silver and graphitic carbon nitride: novel and green synthesis and cooperative photocatalytic activity.

We report a novel synthesis approach employing bamboo leaves as sources of both the C/N dopant and reductant to the formation of C/N co-doped TiO2 modified with Ag and g-C3N4 (Ag/CN-TiO2@g-C3N4). In this case, the ternary composite has a hierarchical structure and a large surface area, which increases the contact area of reactants. Degradation of rhodamine B (RhB) and hydrogen generation were carried out to evaluate the photocatalytic activity of as-prepared samples under visible light irradiation. It is found that with respect to single and binary catalysts, the Ag/CN-TiO2@g-C3N4 ternary composite shows the highest photocatalytic activity (degradation of RhB, H2 evolution from water splitting) as a result of the fast generation, separation and transportation of the photogenerated carriers, which was evidenced by photoluminescence measurements and free radical/hole scavenging experiments. At last, a possible photocatalytic mechanism under visible light irradiation was proposed. The novel and green synergistic approach presented here could provide a facile yet effective method for designing other visible light active non-metal co-doped TiO2 based photocatalysts with enhanced activity and high chemical stability.