TiO2 Lattice Research Articles

Effect of Si on the Oxidation Behaviors of Ti3 Al1-x Six C2 at 1000 °C.

In this work, Ti3 Al1-x Six C2 (x=0, 0.2, 0.4, and 0.6) with Al/Si solid solution structure are synthesized, and the effects of Si on their oxidation behaviors at 1000 °C are evaluated. The addition of Si not only contributes to the formation of Ti5 Si3 impurity but also affects the composition of the oxide scale. Particularly, the incorporation of Si in the TiO2 lattice is demonstrated, which alters the formation energy of the (110) plane in TiO2 , thus leading to the preferential growth of Si-doped TiO2 to dendritic congeries. Moreover, the Si addition is believed to affect mass transportation during the oxidation process, which accelerates the formation of a continuous Al2 O3 layer in the oxide scale. With an optimized Si content, the oxidation of Ti3 Al1-x Six C2 is restrained. However, with excess Si content, the continuity of the resulting Al2 O3 layer is destroyed, thus the oxidation rate rises again.

Improved photoactivity of TiO2 photoanode of dye-sensitized solar cells by sulfur doping

The photoactivity of the photoanode determines the power conversion efficiency of dye-sensitized solar cells (DSSC). TiO2 has come up as a potential photoanode in DSSC but it has several drawbacks, including large trap density due to lattice defect that influences carrier transport, interfacial charge transfer, and carrier transport. Here we present an effective approach to improve the TiO2 photoanode photoelectrical properties by chalcogenide ion doping, i.e. sulfur (S), that compensates the oxygen vacancy in the TiO2 lattice, enhancing the photoactivity at the visible region, reducing trap density and increasing the photovoltaic process in DSSC device. S doping in the TiO2 lattice was achieved by thiourea treatment. Our result shows that the S doping improves the interfacial charge transfer and reduced the trap density, improving the carrier lifetime and power conversion efficiency. The champion device, S-doped TiO2 with 0.3 M thiourea treatment, produces the DSSC with power conversion efficiency as high as 4.56%, which is two times higher than the DSSC using pristine TiO2. The S doping should find a potential approach for enhancing the photoactivity of the TiO2 photoanode of the DSSC device.

Thin film transistor based on epitaxial Ta doped titanium dioxide film

Ta doped titanium dioxide (TiO2:Ta) films were deposited by a metalorganic chemical vapor deposition (MOCVD) system. X-ray diffraction (XRD) measurement revealed the TiO2:Ta films with low Ta contents (≤4.0 at.%) to be epitaxial films of anatase phase. X-ray photoelectron spectroscopy (XPS) measurement showed that Ta element only existed as Ta5+ in TiO2 lattice without other valence states. The electrical characteristics of the films could be modified through Ta doping. The minimum resistivity was obtained at Ta content of 2.0%. As Ta content increased, the carrier concentration increased from 4.9 × 1017 to 1.3 × 1019cm−3 while the Hall mobility decreased from 20.4 to 3.07 cm2V−1s−1. The deposited TiO2:Ta films all presented high visible transparency over 93.0%. A thin-film transistor based on 1.0% Ta-doped TiO2 film was fabricated, which exhibited high performances with a ION/IOFF ratio of 7.5 × 107, a subthreshold swing of 0.55 V/decade, and a saturation mobility of 3.4 cm2V−1s−1.

Ion beam irradiation: Novel approach for preparation of Ag coated N doped nanocrystalline anatase TiO2 films

Herein, a novel approach of ion beam irradiation (nitrogen beam dose ∼ 1013 ions/cm2, 40 keV for 30 min in ultra-high vacuum conditions) is explored for the preparation of nanocrystalline anatase TiO2 modified with nitrogen (N) and silver (Ag). The prepared materials characterized using XRD, Raman, UV–Visible spectroscopy, EIS and wettability techniques. The structural-optical studies revealed the interstitial and/or substitutional doping of N in O-Ti-O matrix supported by Williamson-Hall lattice strain values and dispersion of Ago particles at the TiO2 surface. Raman spectra confirmed the crystallization of anatase TiO2 wherein red shifting-broadening of Raman active modes are due to the phonon confinement and structural defects due to favored substitutional N3– doping in TiO2 lattice. The higher values of Z′, Z″, and RCT in Nyquist plots and the blue shift of ωmax in Bode plots for irradiated films further supported the substitutional doping of N rather than the interstitial one.

Reduction of Pertechnetate by Chemical and Photochemical Approaches and Incorporation of Tc(IV) into Titanium Dioxide

AbstractTechnetium‐99 is a prevalent fission product from nuclear waste. The long half‐life (211,000 yr) and environmental mobility of pertechnetate (TcO4−) render Tc particularly challenging to isolate and stabilize. Here we present two approaches for development of potential wasteforms using titanium dioxide, TiO2. Approach 1 is a low temperature chemical synthesis of TiO2 doped with Tc(IV) from TcO4− intended to mimic the Tc waste stream from the UREX family of separations and removes 98.5 % of the Tc, mainly present as edge‐shared Tc(IV) pairs. Approach 2 utilizes TiO2 to photocatalytically reduce TcO4− to Tc(IV) stabilized on the surface of or within the TiO2 lattice. The %Tc removed from solution and adsorbed to TiO2 is pH dependent, with the maximum Tc(IV) adsorbed at pH 3–4 as either TcO2 or edge‐sharing Tc(IV) octahedra. The Tc(IV)‐TiO2 composites materials formed by both approaches are suitable for consolidation into a dense wasteform by Hot Isostatic Pressing (HIPing).

Mechanosynthesis of Mesoporous Bi-Doped TiO2: The Effect of Bismuth Doping and Ball Milling on the Crystal Structure, Optical Properties, and Photocatalytic Activity

In this work, we reported obtaining mesoporous Bi-doped TiO2 by mechanosynthesis and bismuth loading of 0%, 1%, 3%, 5%, and 10% (milled TiO2, TiO2 Bi 1%, TiO2 Bi 3% TiO2 Bi 5%, and TiO2 Bi 10%, respectively). The effect of bismuth doping and ball milling on the crystal structure, optical properties, and photocatalytic performance of Bi-doped TiO2 mesoporous samples under UV, visible, and sun irradiation was investigated. According to the results of the Rietveld refinement, the estimated chemical formulas for the TiO2 Bi 1%, TiO2 Bi 3%, TiO2 Bi 5%, and TiO2 Bi10% samples were Ti0.99Bi0.01O2, Ti0.97Bi0.03O2, Ti0.96Bi0.04O2, and Ti0.91Bi0.09O2 respectively. The incorporation of Bi into the TiO2 lattice causes the crystallite size to decrease and, consequently, the absorption spectrum of TiO2 to extend into the visible region of the electromagnetic spectrum, resulting in a lower band gap (Eg) value. Bi-doped TiO2 mesoporous samples had Eg values of 2.90 eV, 2.83 eV, 2.77 eV, and 2.70 eV for the TiO2 Bi 1%, TiO2 Bi 3%, TiO2 Bi 5%, and TiO2 Bi 10% samples, respectively. Photocatalytic removal of methylene blue (MB) data fit well for second-order kinetics. Photocatalytic activity increase followed the order of TiO2 Bi 5% > TiO2 Bi 10% > TiO2 Bi 3% > TiO2 Bi 1% > pristine TiO2. The TiO2 Bi 5% sample exhibited excellent photocatalytic performance for MB photodegradation under natural sunlight (89.2%).

Green synthesis of Mn-doped TiO2 nanoparticles and investigating the influence of dopant concentration on the photocatalytic activity

• An environmentally friendly method for preparing photocatalysts to treat organic dyes. • A green synthesis approach is adopted to prepare Mn-doped TiO 2 nanoparticles. • Methylene blue is degraded most efficiently using a 0.05% Mn-TiO 2 catalyst. • 0.1 g L -1 of catalyst is found to remove 86% of Methylene blue after 35 minutes. • The regeneration of the Mn 4+ /Mn 2+ cycle is crucial for photocatalytic activity. A tea plant extract is used in the presence of titanium and manganese sources to synthesize three different concentrations of Mn x Ti 1-x O 2 (x=0.03, 0.05, and 0.1). By substituting Ti atoms for Mn, the lattice of TiO 2 is successfully incorporated with Mn. The degradation of Methylene Blue (MB) in the presence of visible light is used to test the photocatalytic activity of the synthesized samples. Among the Mn-doped TiO 2 samples, the highest degradation ratio is observed for samples with a dopant concentration of 0.05 at%. A dose of 0.1 g L -1 and 5 mM of Mn-TiO 2 is found to remove 86% of MB after 35 minutes of reaction. Mn x Ti 1-x O 2 is critically important for speeding up the MB degradation because of electron transfer between Mn and TiO 2 , and for the regeneration of the Mn 4+ /Mn 2+ cycle on its surface. Optical irradiation of the photocatalytic system under visible light led to higher visible photocatalytic activity than pure TiO 2 . We propose a novel and environmentally friendly method for preparing photocatalysts to treat organic dyes.

Optical, structural, morphological and chemical properties of doped TiO2 nanoparticles with FeCl3

To achieve high photocatalytic activity, TiO2 nanoparticles nanoparticles require an excitation source in ultraviolet radiation. Incorporating chemical elements into the TiO2 lattice can tune its band gap, resulting in an edge-shifted red absorption to reduce energies, improving photocatalytic performance in the visible region of the electromagnetic spectrum. In this research, TiO2 semiconductor nanoparticles were subjected to a doping process using iron chloride (FeCl3) powder to activate photocatalysis under visible light and consequently improve pollutant capture. To study the effectiveness of the doping process, the main ratios (1:1), (1:1.622) and (1:3) of TiO2:FeCl3 were evaluated using Diffuse Reflectance Spectroscopy (DRS), X-ray diffraction (XRD), Fourier-Transform Infrared Spectroscopy (FTIR) and Scanning Electron Microscopy (SEM). The main results of this research show that doping TiO2 with FeCl3 shifted the absorption edge to longer wavelength values, changing the optical properties of the material and decreasing the band gap (Eg) of TiO2 compared to the undoped TiO2 (reference). There are no relevant differences between the XRD pattern of the samples with TiO2-FeCl3 and TiO2 nanoparticles (reference). The fraction of the anatase phase in doped TiO2 nanoparticles has the same magnitude as the reference TiO2. Regarding FTIR, the Fe-doping process alters the TiO2 reference spectrum, increasing the intensity of hydroxyl bonds and peaks particularly, indicating the Ti-O-Fe bond vibration.

High relative permittivity and excellent dye photo-elimination: Pure and (Zr4+, Y3+, Sb5+) multi-doped anatase TiO2 structure

Herein, multifunctional characteristics including solar photocatalytic, dielectric constant and ac electrical conductivity have been studied for pure and Zr4+, Y3+ and Sb5+ multidoped TiO2 n-type semiconductor. Pure, Zr doped, (Zr, Y) codoped and (Zr, Y, Sb) tridoped TiO2 with chemical compositions of TiO2, Ti0.98Zr0.02O2, Ti0.96Zr0.02Y0.02O2 and Ti0.94Zr0.02Y0.02Sb0.02O2 were prepared via a low cost coprecipitation technique. All compositions reveal a pure single phase of anatase TiO2 structure with different unit cell volume due to the differences in ionic radii between parent cation (Ti4+ = 0.605 Å) and dopants ions (Zr4+ = 0.72 Å), (Y3+ = 0.9 Å) and (Sb5+ = 0.6 Å). Morphological changes for TiO2 particles were seen due to incorporation of Zr4+, Y3+ or Sb5+ cations into TiO2 lattice. Optically, Zr4+, Y3+ and Sb5+ ions cause a red shift for the absorption edge and reduce the width of the bang gap energy of TiO2 as well as enhance its refractive index value. High dielectric constant of 2214 (42 Hz) was detected for Ti0.94Zr0.02Y0.02Sb0.02O2 composition. Ti0.94Zr0.02Y0.02Sb0.02O2 sample reveals the highest ac electrical conductivity (σac) values compared to undoped TiO2, Ti0.98Zr0.02O2 and Ti0.96Zr0.02Y0.02O2 samples. High efficiency (∼100%) and fast (20–40 min) solar photodegradation characteristics for 10 ppm Congo red (CR) was realized via TiO2 and Ti0.96Zr0.02Y0.02O2 catalysts. For 40 ppm CR, pure TiO2 exhibits a high photocatalytic activity of 80% after 120 min of sunlight irradiation. Interestingly, this study also illustrates that the starting materials (titanium butoxide-butanol solvent) used in the synthesis process play a significant role in the phase structure as well as the ultimate photocatalytic properties of TiO2 based compositions.

Effect of Vacuum-Sealed Annealing and Ice-Water Quenching on the Structure and Photocatalytic Acetone Oxidations of Nano-TiO2 Materials.

In the current research, P25 TiO2 materials sealed in quartz vacuum tubes were subject to annealing and ice-water post-quenching, with the effects on TiO2 structures, morphology, and photocatalytic activity being studied. It is shown that the vacuum-sealed annealing can lead to a decrease in the crystallinity and temperature of anatase-to-rutile phase transition. A disorder layer is formed over TiO2 nanoparticles, and the TiO2 lattices are distorted between the disorder layer and crystalline core. The ice-water post-quenching almost has no effect on the crystalline structure and morphology of TiO2. It can be seen that the vacuum-sealed annealing can generate more defects, and the electrons are mainly localized at lattice Ti sites, as well as the percentage of bulk oxygen defects is also increased. Although further ice-water post-quenching can introduce more defects in TiO2, it does not affect the electron localization and defect distribution. The vacuum-sealed annealing process can increase the photocatalytic acetone oxidations of the anatase phase TiO2 to some extent, possibly because of the defect generation and Ti3+ site formation; the further ice-water quenching leads to a decrease in the photocatalytic activity because more defects are introduced.

Selective hydroxylation of benzene to phenol via C[sbnd]H activation over mesoporous Fe2O3-TiO2 using H2O2

The omnipresence of CH bonds in organic molecules enamors chemists for the functionalization of CH bonds towards value-added molecular scaffolds. Mesoporous Fe2O3-TiO2 mix-oxide catalyst has been successfully synthesized via a triblock-copolymer (P123) mediated sol-gel method and catalytically tested in selective hydroxylation of benzene. The as-synthesized catalysts were comprehensively characterized by powder XRD, Raman spectroscopy, FT-IR, N2-physisorption, FESEM, HRTEM, XPS, and NH3-TPD techniques. The physicochemical characterizations evidence that Fe(III) ions incorporate into the pure anatase TiO2 lattice framework and the crystallite size decreases as iron concentration increases. The XPS analyses confirm the Fe3+ state (BE 710.3 eV) in Fe-O-Ti with a peak at 712.1 eV for Fe3+ of Fe2O3. The NH3-TPD results show that the 5 wt% Fe-TiO2 has a higher total acidity of 105 µmol/g. Interestingly, a further increase in iron amount decreases the total acidity. Herein, we observe that the surface acidity directs the selectivity towards phenol. The effect of different reaction parameters was carefully investigated. Under the optimized conditions, 5% Fe-TiO2 with notified strong acid sites gives a higher phenol yield of 31.2% with > 99% selectivity; moreover, the catalyst is reusable at least four times.

The Role of Nitrogen-Doped TiO2 Supported by Platinum Catalyst Synthesized via Various Mode Preparations for Photocatalytic Enhancement.

The limitations of TiO2 as a photocatalyst such as the larger bandgap energy, which only activates under the UV region, give a lower photocatalytic activity. This study reports the role of the N and Pt co-dopant on the modification of the TiO2 photocatalyst for photocatalytic degradation of methylene blue dye under different mode preparations, i.e., sequential and vice-versa modes. The sequential mode preparation of the N and Pt co-dopant TiO2 photocatalyst consisted of the initial preparation of the N-doped TiO2 (N-TiO2) under the calcination method, which was then further doped with platinum (Pt) through the photodeposition process labeled as NPseq-TiO2, while the vice-versa mode was labeled as PNrev-TiO2. About 1.58 wt.% of N element was found in the NPseq-TiO2 photocatalyst, while there was no presence of N element detected in PNrev-TiO2, confirmed through an elemental analyzer (CHNS-O) and (EDX) analysis. The optimum weight percentage of Pt for both modes was detected at about ±2.0 wt.%, which was confirmed by inductively coupled plasma-emission spectroscopy (ICP-OES). The photoactivity under methylene blue (MB) dye degradation of the NPseq-TiO2 photocatalyst was 2 and 1.5 times faster compared to the unmodified TiO2 and PNrev-TiO2, where the photodegradation rates were, ca., 0.065 min-1 and 0.078 min-1, respectively. This was due to the N elements being incorporated with the TiO2 lattice, which was proven by UV-Vis/DRS where the bandgap energy of NPseq-TiO2 was reduced from 3.2 eV to 2.9 eV. In addition, the N generated a stronger PL signal due to the formation of oxygen vacancies defects on the surface of the NPseq-TiO2 photocatalyst. The higher specific surface area as well as higher pore volume for the NPseq-TiO2 photocatalyst enhanced its photocatalytic activity. Moreover, the NPseq-TiO2 showed the lowest COD value, and it was completely mineralized after 7 h of light irradiation. The preparation order did not affect the Pt dopant but did for the N element. Therefore, it is significant to investigate different mode preparations of the N and Pt co-dopant for the modification of TiO2 to produce a good-quality photocatalyst for photocatalytic study under the photodegradation of MB dye.

Porous sulfur-doped titanium dioxide for improving photocatalytic VOC removal and biological disinfection under low intensity fluorescent light

In this research work, we have utilized the probe sonication assisted sol-gel method to prepare highly active porous sulfur doped TiO2 (PST). The cationic sulfur (S6+) doped into the TiO2 lattice created a new intermediate level (S2p) between the valence band (VB) and conduction band (CB). The doping of sulfur on TiO2 led to additional absorption features in the visible region. The spherical-shaped porous PST nanoparticles were confirmed from SEM which influence the active sites for the photocatalytic performance. Instantaneous decomposition of pollutant p-xylene, a carcinogenic volatile organic compound, was accomplished using the stable PST photocatalyst working under low intensity fluorescent visible light. PST characterized by a pure anatase crystal structure, a high specific surface area of 76m2/g (1.52 times greater than commercial P25) and a pore size of 17 nm favored a substantially increased adsorption of VOC molecule on the catalyst surface and enhanced the photocatalytic activity with respect to p-xylene decomposition. Disinfecting effect of PST photocatalyst against E.coli was also investigated. Therefore, the high efficient PST functions as a multipurpose photocatalyst and could be used in air purification treatment due to its high recyclability.

Ytterbium doping reduces the dark current of UV photoelectric detector based on TiO2

Improved performance of TiO2-based UV photodetectors needs functional improvements in materials. Doping can modulate the electron and hole concentration and band structure of materials. This work shows that doping Yb into TiO2 improves the performance of TiO2-based UV photodetectors. It is found experimentally that doping Yb can cause Yb ions to replace Ti ions in lattice of TiO2, which is conducive to adjusting the physical and chemical properties from the perspective of energy band engineering. The dark current of the detector was less than 1 nA at bias of 5 V. Under UV radiation, the device achieved a maximum switching rate of 3.64 ⅹ 103 when the doping concentration of Yb was 5%, and the recovery time dropped from 1.4 s to 0.65 s.

Microstructure, optical and magnetic properties of TiO2/CuO nanocomposites synthesized by a two-step method

TiO2/CuO composites in different ratios were prepared via a two-step method. X-ray diffraction and transmission electron microscopy results indicated that part of Cu2+ substituted Ti4+ in the TiO2 lattice in the composite, leading to Cu2+-substituted sites in the TiO2 lattice as well as Cu2+ species located in the CuO lattice. Scanning electron microscopy revealed a morphology change in the sample from a three-dimensional structure to a two-dimensional structure while forming an interface between TiO2 and CuO. X-ray photoelectron spectroscopy and Raman spectra showed that there are oxygen vacancies (VO) and Ti3+ in the lattice. UV–vis absorption spectra exhibited a widening of the absorption range and a decrease in the bandgap with increasing amount of CuO in the TiO2/CuO composites. Additionally, the composites exhibited room-temperature ferromagnetism (RTFM), as can be explained by the indirect double-exchange model, which is related to VO and the exchange interaction between the 3d orbitals of Ti3+ and Ti4+ at the interface.

Dual Activation of Molecular Oxygen and Surface Lattice Oxygen in Single Atom Cu1 /TiO2 Catalyst for CO Oxidation.

The in-depth mechanism on the simultaneous activation of O2 and surface lattice O2- on one active metallic site has not been elucidated yet. Herein, we report a strategy for the construction of abundant oxygen activation sites by rational design of Cu1 /TiO2 single atom catalysts (SACs). The charge transfer between isolated Cu and TiO2 support generates abundant CuI and 2-coordinated Olat sites in Cu1 -O-Ti hybridization structure, which facilitates the chemisorption and activation of O2 molecules. Simultaneously, the Cu1 -O-Ti induced TiO2 lattice distortion activate the adjacent surface lattice O2- , achieving the dual activation of O2 and surface lattice O2- . The Cu1 -O-Ti active site switches the CO oxidation mechanism from Eley-Rideal (80 °C) to Mars-van Krevelen route (200 °C) with the increase of reaction temperature. The dual activation of O2 and surface lattice O2- can by modulating the electron properties of SACs can boost the heterogeneous catalytic oxidation activity.

Dual Activation of Molecular Oxygen and Surface Lattice Oxygen in Single Atom Cu1/TiO2 Catalyst for CO Oxidation

AbstractThe in‐depth mechanism on the simultaneous activation of O2 and surface lattice O2− on one active metallic site has not been elucidated yet. Herein, we report a strategy for the construction of abundant oxygen activation sites by rational design of Cu1/TiO2 single atom catalysts (SACs). The charge transfer between isolated Cu and TiO2 support generates abundant CuI and 2‐coordinated Olat sites in Cu1−O−Ti hybridization structure, which facilitates the chemisorption and activation of O2 molecules. Simultaneously, the Cu1−O−Ti induced TiO2 lattice distortion activate the adjacent surface lattice O2−, achieving the dual activation of O2 and surface lattice O2−. The Cu1−O−Ti active site switches the CO oxidation mechanism from Eley‐Rideal (80 °C) to Mars–van Krevelen route (200 °C) with the increase of reaction temperature. The dual activation of O2 and surface lattice O2− can by modulating the electron properties of SACs can boost the heterogeneous catalytic oxidation activity.

The synergic removal mechanism for photothermocatalytic toluene over single-atom Pt/TiO2 catalysts via flame spray pyrolysis

Photothermocatalytic oxidation is an environmentally-friendly, low-temperature, and high-efficient method to remove the air pollutant. Yet, the lack of active, inexpensive, and superior stability catalysts has greatly limited its extensive utilization. In this work, the effect of single-atom Pt loading on TiO2 support has been theoretically and experimentally studied to improve photothermocatalytic performance for the toluene combustion through flame spray pyrolysis (FSP). Pt loading can play two crucial roles into TiO2 optimization: (1) The low-valence Pt cation incorporated into TiO2 lattice is dramatically responsible for the anatase-rutile transformation (ART) and formation of sufficient oxygen vacancies; (2) Introducing the defect energy level and Pt-3d orbitals remarkably promote the charge separation efficiency of single-atom catalysts. Moreover, the existence of single-atom Pt nanoparticles can signally boost the activity of surface adsorbed and lattice oxygen, as well as substantially reduce the oxygen vacancy formation energy. Thus, the toluene removal under light irradiation reaches 90% conversion below 160 °C and is maximally 18 °C lower than that under only thermocatalytic oxidation. It is attributed to larger specific surface area (SSA), outstanding low-temperature reducibility, extremely dispersed hybrid PtOx, more surface active oxygen, and higher mobility of bulk oxygen. Interestingly, when the oxygen-fuel equivalent ratio φ distinctly increases by shifting precursor solvent from xylene to ethanol, the photothermocatalytic property of toluene can be remarkably enhanced on single-atom Pt catalysts. It is due to the higher Pt dispersion resulting from more intense burning and drastic turbulent mixing, as well as the superior ratio of the metallic Pt active sites originating from higher flame temperature. Eventually, the rate-determining step of C7H8 combustion on Pt/TiO2 and Cu/TiO2 slab are all the CC bond fracture of maleic anhydride to form acetic anhydride species, with the energy barriers of 112.03 and 188.74 kJ/mol, respectively.

Development of immobilised sunlight active W-Mo/Mo-V/V-W co-doped TiO2 photocatalyst by plasma electrolytic oxidation

W-Mo/Mo-V/V-W co-doped TiO2 photocatalyst for the effective degradation of MB (methylene blue) dye under sunlight irradiation was successfully prepared by one-step Plasma Electrolytic Oxidation (PEO) process. The XRD, XPS, and EDS results revealed that W/Mo/V were co-doped in the TiO2 lattice. The highest redshift in the light absorption edge is recorded for the sample MV (Mo-V co-doped TiO2) with a bandgap of 2.51 eV, whereas the bandgaps for WM (W-Mo co-doped TiO2) and VW (V-W co-doped TiO2) are recorded as 2.96 eV and 2.58 eV, respectively. The co-doped photocatalysts show a typical PEO structure with a high degree of porosity favouring the dye adsorption ability. EIS, LSV, and PL analysis confirmed that the co-doped coatings pose a high degree of charge separation, suppressed charge carriers' recombination, and increased the ability to produce photocurrent. Under direct sunlight irradiation, the sample MV showed the highest photocatalytic efficiency, confirmed by MB dye degradation, then the other co-doped and undoped TiO2. This can be attributed to the synergetic effects of intense visible light absorption in the solar spectrum and the reduced charge carriers' recombination rate by acting as the trapping sites for photogenerated electrons and holes. Finally, this immobilised co-doped photocatalyst developed by the PEO process is a promising system in the quest to establish a renewable energy-assisted strategy for textile wastewater treatment application. • Developed direct sunlight active W-Mo/Mo-V/V-W co-doped TiO 2 on Cp-Ti by PEO. • Mo-V co-doped TiO 2 (Eg of 2.41 eV) shows the highest redshift in light absorption. • Immobilised Mo-V co-doped TiO 2 shows the highest dye degradation and mineralisation. • Low Eg and e + /h − recombination rate is due to the synergetic effect of V and Mo.

Examination of the doping effects of samarium (Sm3+) and zirconium (Zr4+) on the photocatalytic activity of TiO2 nanofibers

Pure and samarium (Sm3+) - or zirconium (Zr4+)-doped TiO2 nanofibers were synthesized by electrospinning method followed by calcination at 500 °C for 1 h. As-spun fibers were smooth, straight and continuous, whilst EDS analysis confirmed the fiber composition and incorporation of dopants in the fibers. Doping with Sm3+ and Zr4+ greatly inhibited the phase transformation of anatase to rutile, by surrounding of Sm3+ ions through formation of Ti-O-Sm bonds and by replacement of Ti4+ ions with larger Zr4+ ions. This was confirmed by HRTEM and SAED analysis. The size of nanofibers was determined to be 133 nm, 175 nm and 155 nm for pure, (0.5%)Sm3+:TiO2 and (1%)Zr4+:TiO2, respectively. After calcination, TiO2 crystal lattice with interplanar spacing of 0.353 nm of (101) crystal plane was not significantly disturbed by Sm doping whilst crystal lattice spacing of 0.357 nm of (101) planes of anatase phase in case TiO2:1.0%Zr4+, significantly differs from the value of pure TiO2 (0.352 nm), thus implying that Zr was doped into substitutional sites of the TiO2 lattice. The indirect band gaps were calculated to be in the range 3.07–3.24 eV. TiO2:0.5%Sm3+ and TiO2:1.0%Zr4+ exhibited higher specific surface area, of 47.1 and 59.4 m2/g, respectively, than pure TiO2 fibers (19.7 m2/g). Effects of Sm3+ and Zr4+ dopant content on the photodegradation efficiency of methylene blue (MB) were studied. TiO2:0.5%Sm3+ and TiO2:1.0%Zr4+ nanofibers have shown the highest photocatalytic activity of 97% and 98% with constant rates 0.01768 min−1 and 0.01939 min−1, respectively, within180 min irradiation under visible light.