Pristine TiO2 Research Articles

2D/1D BiOBr/TiO2 flexible nanofibrous film heterojunction photocatalyst for tetracycline degradation

Semiconductor photocatalysis is an ideal and sustainable solution to effectively remove Tetracycline (TC). Herein, a hierarchical flexible nanofibrous film (NF) heterojunction photocatalyst of BiOBr/TiO2 was fabricated via a combination of electrospinning and solvothermal method, obtaining the two-dimensional (2D) BiOBr nanosheets uniformly anchored on the surface of one-dimensional (1D) TiO2 nanofiber, and the amount of BiOBr significantly influences the physicochemical properties of the heterojunction photocatalyst, the optimal sample of BT-2 manifests large pore size and high surface area, prominent visible light response ability and narrow band gap as well as outstanding charge separation efficiency, thus achieves significantly enhanced photocatalysis activity for TC degradation, which is about twice higher than that of the pristine TiO2 NF. More importantly, the BT-2 sample also displays high reusability and stability over a 10-cycle period and can be easy to recover. Meanwhile, the radical scavenging experiments and electron spin resonance characterization reveal that ·O2– and h+ occupy an irreplaceable role in degrading TC. Moreover, regarding the analysis of intermediates and density functional theory calculations, the TC photodegradation mechanism and pathways are proposed. Our finding offers a prospective solution for designing BiOBr/TiO2 heterojunction recyclable photocatalysts for efficient TC photodegradation.

Effect of ethylene glycol chelated on ultrathin TiO2(B) nanosheets on the photocatalytic selective benzyl alcohol oxidation

The two-dimensional (2D) photocatalysts have been paid intensive attention in catalysis due to their excellent activity, which was greatly improved by the higher exposure of active sites and a facile reaction platform, and the separation efficiency of charge carriers. Herein, TiO2(B) nanosheets, which were synthesized via solvothermal method in ethylene glycol, could photocatalytically oxidize benzyl alcohol to benzaldehyde with high selectivity. The study revealed that the material's photocatalytic performance is highly influenced by the surface-chelated ethylene glycol. The pristine TiO2(B) was effective in selectively photocatalytic oxidizing benzyl alcohol, achieving a 94.5 % conversion, while the conversion decreased to 55 % after the elimination of the surface ethylene glycol. The presence of ethylene glycol on the surface of TiO2(B) nanosheets benefits the transfer of photogenerated charge carriers and improves charge separation efficiency. It is favorable for the selective formation of singlet oxygen (1O2) species, which results in enhanced photocatalytic activity and selectivity. We believe that our findings can shed light on the importance of the surface species and properties of photocatalysts in photocatalysis, and pave an avenue for the design and preparation of high-efficiency photocatalysts with unique surface properties.

Photocatalytic production of ethylene and propionic acid from plastic waste by titania-supported atomically dispersed Pd species

Current chemical recycling of bulk synthetic plastic, polyethylene (PE), operates at high temperature/pressure and yields a complex mixture of products. PE conversion under mild conditions and with good selectivity toward value-added chemicals remains a practical challenge. Here, we demonstrate an atomic engineering strategy to modify a TiO 2 photocatalyst with reversible Pd species for the selective conversion of PE to ethylene (C 2 H 4 ) and propionic acid via dicarboxylic acid intermediates under moderate conditions. TiO 2 -supported atomically dispersed Pd species exhibits C 2 H 4 evolution of 531.2 μmol g cat −1 hour −1 , 408 times that of pristine TiO 2 . The liquid product is a valuable chemical propanoic acid with 98.8% selectivity. Plastic conversion with a C 2 hydrocarbon yield of 0.9% and a propionic acid yield of 6.3% was achieved in oxidation coupled with 3 hours of photoreaction. In situ spectroscopic studies confirm a dual role of atomic Pd species: an electron acceptor to boost charge separation/transfer for efficient photoredox, and a mediator to stabilize reaction intermediates for selective decarboxylation.

Physicochemical and Electrochemical Properties of Materials Based on Titanium Suboxides

The influence of the synthesis conditions on the surface morphology, phase composition, and electrocatalytic activity of materials in oxygen and hydrogen evolution reactions was investigated. For instance, the slopes in the potential vs the logarithm of the current density dependencies during oxygen evolution were 221 and 109 mV/dec for TiO2 nanotubes and platinum-coated layers, respectively. In the latter case, small deviations may be attributed to the structural heterogeneity of the material or the developed surface of the coating. As for pristine TiO2 nanotubes, an atypical Tafel slope was observed, almost twice the theoretical value, indicating the presence of a semiconductor component in the electrode capacitance. Studies showed that the materials are n-type semiconductors. The cathodic polarization stage leads to the formation of titanium suboxides in the nanotube recovery phase, contributing to an increase in the material electrical conductivity. This also allows for the creation of a porous developed surface matrix for the electrodeposition of catalytic metal layers. Tafel slopes were calculated for the investigated materials in the hydrogen evolution reaction. For TiO2 nanotubes, a slope of 175 mV/dec was observed. The material surface was partially blocked by hydroxides, resulting in a low num-ber of active centers for the hydrogen evolution, and the polarization curve had a steep slope. In the case of TiO2 nanotubes coated with a platinum layer, a high number of cationic vacancies in the matrix and a deficit of oxygen ions facilitated the mobility of platinum atoms, leading to the emergence of a large number of active centers for the hydrogen evolution. As a result, the Tafel slope of the polarization curve was found to be 30 mV/dec.

Effect of chromium doping on the band gap tuning of titanium dioxide thin films for solar cell applications

A simple and inexpensive spray pyrolysis deposition (SPD) approach was used to produce TiO2 and Cr (2–8) at.%-doped TiO2 thin films. To explore the morphological features of the films, FE-SEM micrographs were used and found that 6 and 8 at.% TiO2:Cr films had fibrous patterns with diameters of 0.45 and 0.78 μm, respectively, while the remainder of the films were agglomerated particles. From X-ray diffraction investigation, it was found that the TiO2 thin films had an anatase crystal phase (tetragonal) up to 6 at.% Cr doping, while an anatase-rutile mixed crystalline phase was identified for 8 at.% Cr doping. The crystallite size of the pristine TiO2 film was 35 nm, while for TiO2:Cr films, it ranges from 35 to 46 nm. The Fizeau fringes technique was employed to measure the thickness of the TiO2 film and 165 nm was found for pristine TiO2 and 164–180 nm for TiO2:Cr films. UV–visible spectroscopy was used to study optical properties such as absorbance, refractive index, optical band gap, dielectric constant, and optical conductivity. As the Cr concentration increases, the optical band gap decreases from 3.40 eV to 2.70 eV. Using the four-point probe method, it was found that the resistivity changes with temperature and is also affected by the Cr content.

Defective heterojunctions in CO2 photoreduction: Enabling ultrafast interfacial charge transfer and selective methanation

This study achieved the goal of enhancing photocatalytic methane production and selectivity by constructing a S-scheme heterojunction of TiO2/g-C3N4 followed by conducting a mild-temperature hydrogen reduction to remove hydroxyl groups from the catalyst surface, thereby generating rich vacancies-related active sites. The rate of CO2 photoreduction to CH4 under pure water from the H2-Ti-CN sample is around 27.4 μmol g−1 h−1 with 93.6% selectivity, which is 39.1-fold and 5.59-fold that of pristine g-C3N4 and TiO2, respectively. In addition, the DFT calculation indicates that the vacancies created via hydrogen reduction-mediated heterojunctions effectively tune the energy barrier, resulting in a decrease in the production of the two-electron product CO and concurrently improves the selectivity of the eight-electron reaction. The significantly enhanced photocatalytic performance is ascribed to defects fostering ultrafast charge carrier transfer channels and facilitating the transfer of light-excited charges to the surface, thereby enhancing its high redox capabilities in catalytic reactions.

The effect of in-situ Pr6O11 phase formation on photocatalytic Performance: Mono azo dye degradation

The structural properties of TiO2, which finds wide application due to its excellent properties, can be improved especially by doping with transition metals to treat wastewater containing dyestuffs in a cheap, sustainable and environmentally responsible way. The positive impact of in situ Pr6O11 phase formation on the catalytic characteristics of the praseodymium ion doped (Pr-TiO2) photo catalyst produced by the acid sol gel method is highlighted in this study. Pr ion doping concentration of 1 wt% and calcination temperature of 400° C were selected. The properties of a Pr6O11/TiO2 composite structure (Pr-TiO2) synthesized utilizing XRD, XPS, and FTIR methods are discussed. Furthermore, the surface area of the pristine TiO2 photocatalyst was 19.22 (m2.g−1) and rose to 101.51 (m2.g−1) in the Pr-TiO2 catalyst, according to BET surface area measurements. The adsorption properties and photocatalytic activity of the catalyst were determined by the examination of the mono azo dyestuff Basic Blue 41 (BB41) degradation in a batch reactor using suspended system photocatalysis (ASF). No oxidation agents were used in this system. Azo dyestuff removal efficiency was measured by total organic carbon (TOC) and the color pollution change of wastewater was measured by UV–vis spectrophotometer.

Simultaneous chelated heavy metals removal and sludge recovery through titanium coagulation: From waste to resource

Green methods for chelated heavy metals treatment and recovery are essential for coordinated development of resources and environment. Herein, a simple and competent method, titanium salt (TiCl4) coagulation was developed to remove and recycle chelated heavy metals. Our results revealed that this method proved to be effective for metals-citrate [Cu(II), Ni(II), Zn(II) and Cr(VI)], achieving removal efficiencies of 95 %, 92 %, 99 %, and 99 % within 30 min, surpassing direct alkaline precipitation and well-used Fe(III) coagulation. Whereafter, the copper-containing sludge was successfully transformed into copper-doped titanium dioxide (TiO2) photocatalysts by facile calcination. Through comprehensively investigating physicochemical properties by a suite of characterization techniques, we confirmed that doping of Cu induced bandgap narrowing, high specific surface area as well as the formation of oxygen vacancy. Accordingly, the recycling photocatalysts showed remarkable enhanced photocatalytic performance than the pristine TiO2, achieving improvement in the degradation efficiency of 82 %, 61 % and 67 % for carbamazepine(CBZ), bisphenol A (BPA) and methyl orange (MO). In addition, both radical (OH and O2−) and non-radical (1O2 and h+) pathways synergistically contributed to the removal of organic pollutants during photocatalysis. Ultimately, based on economic feasibility assessment and life cycle assessment (LCA), the copper-containing titanium coagulation sludge reuse for photocatalyst could bring lower carbon emissions, reduced environmental risks and higher economic benefits. The elucidation of this study provides new insights into the removal and recycle of chelated heavy metals from wastewater by using an environment-friendly and cost-effective method.

Enhancement TiO2 photocatalytic hydrogen production via using ABO3 to construct heterojunction

The lower photogenerated carrier separation efficiency seriously hinders the photocatalytic performance of TiO2. In order to solve this problem, we utilized SrTiO3 particles with low cost, good response to visible light, tunable band structure, and type II heterojunction with TiO2 to improve the photogenerated carrier separation efficiency of TiO2 in this study. The TiO2/SrTiO3 heterojunctions have a larger specific surface area than pristine TiO2, pristine SrTiO3. The results confirmed that the formation of heterostructures reduce the interfacial resistance of charge transfer; the transient and effectively improve the electron-hole pair separation efficiency. The hydrogen production efficiency of TiO2/SrTiO3 heterojunction composite is 807.7 μmolg−1h−1, which is 26 times higher than pure TiO2 nanotubes. This work provides a new way to prepare efficient and low-cost photocatalysts using ABO3.

Surface Hydrogen Bond-Induced Oxygen Vacancies of TiO2 for Two-Electron Molecular Oxygen Activation and Efficient NO Oxidation.

Defect engineering can provide a feasible approach to achieving ambient molecular oxygen activation. However, conventional surface defects (e.g., oxygen vacancies, OVs), featured with the coordinatively unsaturated metal sites, often favor the reduction of O2 to •O2- rather than O22- via two-electron transfer, hindering the efficient pollutant removal with high electron utilization. Herein, we demonstrate that this bottleneck can be well discharged by modulating the electronic structure of OVs via phosphorization. As a proof of concept, TiO2 nanoparticles are adopted as a model material for NaH2PO2 (HP) modification, in which HP induces the formation of OVs via weakening the Ti-O bonds through the hydrogen bond interactions. Additionally, the formed Ti-O-P covalent bond refines the electronic structure of OVs, which enables rapid electron transfer for two-electron molecular oxygen activation. As exemplified by NO oxidation, HP-modified TiO2 with abundant OVs achieved complete NO removal with high selectivity for benign nitrate, superior to that of pristine TiO2. This study highlights a promising approach to regulate the O2 activation via an electronic structure modulation and provides fresh insights into the rational design of a photocatalyst for environmental remediation.

Red Phosphorus Grafted High‐Index (116) Faceted Anatase TiO2 for Z‐Scheme Photocatalytic Pure Water Splitting

AbstractRed phosphorus (RP) is an emerging visible‐light‐responsive photocatalyst, yet the rapid charge recombination has limited photocatalytic hydrogen production activity. In this work, a Z‐scheme heterostructure with RP nanolayer coated on high‐index (116) faceted anatase TiO2 nanoparticles (TiO2@RP) is designed and fabricated via chemical vapor deposition. Compared with pristine TiO2 and RP, the optimized TiO2@RP Z‐scheme heterostructure exhibits a significantly boosted photocatalytic activity for pure water splitting, with hydrogen evolution rate reaching 12.9 µmol·h−1, under simulated solar light irradiation. The strong interfacial interaction and staggered band alignment between (116) faceted TiO2 and RP result in the formation of built‐in electric field, which can drive the directional charge migration from the conduction band (CB) of TiO2 to the valance band (VB) of RP under light irradiation, with photoelectrons and holes of high redox ability maintained at the CB of RP and the VB of TiO2, respectively. This well‐designed heterostructure greatly promotes photogenerated charge separation and migration via a direct Z‐scheme charge transfer pathway.

Photocatalytic Degradation of Emerging Contaminants with N-Doped TiO2 Using Simulated Sunlight in Real Water Matrices

In the present work, the photodegradation performances of N-doped TiO2 photocatalysts with enhanced absorption of visible light were exploited for the abatement of some representative contaminants of emerging concern (CECs). Pristine TiO2 and N-TiO2 were synthesized using hydrothermal (HT) and sol–gel (SG) routes, they were characterized using XRD and UV-Vis spectroscopy, and their band gaps were determined via analysis in diffuse reflectance. Their photodegradation efficiency was tested on a mixture of recalcitrant organic pollutants, namely, benzotriazole, diclofenac, sulfamethoxazole, and bisphenol A, using a solar simulator lamp with two different cut-off filters (λ > 340 nm and λ > 400 nm). The evaluation of the photocatalytic performances was initially carried out in spiked ultrapure water and subsequently in aqueous matrices of increasing complexity such as Po River water and water coming from an aquaculture plant. The exclusive utilization of visible light (λ > 400 nm) highlighted the advantage of introducing the dopant into the TiO2 photocatalyst since this modification allows for the material to be responsive to visible light, which is not sufficient in the case of pristine TiO2 and the higher efficiency of materials obtained via the sol–gel route. Thanks to the doping, improved performance was obtained in both ultrapure water and real water matrices, indicating the potential of the doped material for future applications in the field.

Enhanced Visible Light-Driven Photocatalytic Water-Splitting Reaction of Titanate Nanotubes Sensitised with Ru(II) Bipyridyl Complex.

The ion exchange of Na+ cations was used to photosensitise titanates nanotubes (Ti-NTs) with tris(2,2'-bipyridine)ruthenium(II) cations (Ru(bpy)32+); this yielded a light-sensitised Ti-NTs composite denoted as (Ru(bpy)3)Ti-NTs, exhibiting the characteristic absorption of Ru(bpy)32+ in visible light. Incident photon-to-current efficiency (IPCE) measurements and the photocatalytic reduction of methyl viologen reaction confirmed that in the photosensitisation of the (Ru(bpy)3)Ti-NTs composite, charge transfer and charge separation occur upon excitation by ultraviolet and visible light irradiation. The photocatalytic potential of titanate nanotubes was tested in the water-splitting reaction and the H2 evolution reaction using a sacrificial agent and showed photocatalytic activity under various light sources, including xenon-mercury lamp, simulated sunlight, and visible light. Notably, in the conditions of the H2 evolution reaction when (Ru(bpy)3)Ti-NTs were submitted to simulated sunlight, they exceeded the photocatalytic activity of pristine Ti-NTs and TiO2 by a factor of 3 and 3.5 times, respectively. Also, (Ru(bpy)3)Ti-NTs achieved the photocatalytic water-splitting reaction under simulated sunlight and visible light, producing, after 4 h, 199 and 282 μmol×H2×gcat-1. These results confirm the effective electron transfer of Ru(bpy)3 to titanate nanotubes. The stability of the photocatalyst was evaluated by a reuse test of four cycles of 24 h reactions without considerable loss of catalytic activity and crystallinity.

A Fresh Perspective on the Impact of ZnTiO3 Coupling on the Microstructure and Photocatalytic Properties of TiO2 Fabricated at Varied Temperatures.

ZnTiO3/TiO2 composite photocatalysts were synthesized via the sol-gel technique, and the impact of varying heat treatment temperatures (470, 570, 670 °C) on their crystalline arrangement, surface morphology, elemental composition, chemical state, specific surface area, optical characteristics, and photocatalytic efficacy was systematically investigated. The outcomes revealed that, as the temperature ascends, pure TiO2 undergoes a transition from anatase to rutile, ultimately forming a hybrid crystal structure at 670 °C. The incorporation of ZnTiO3 engenders a reduction in the TiO2 grain dimensions and retards the anatase-to-rutile phase transition. Consequently, the specimens manifest a composite constitution of anatase and ZnTiO3. In contrast, for pure TiO2, the specimen subjected to 670 °C annealing demonstrates superior photocatalytic performance due to its amalgamated crystal arrangement. The degradation efficacy of methylene blue (MB) aqueous solution attains 91% within a 60-min interval, with a calculated first-order reaction rate constant of 0.039 min-1. Interestingly, the ZnTiO3/TiO2 composite photocatalysts exhibit diminished photocatalytic activity in comparison to pristine TiO2 across all three temperature variations. Elucidation of the photocatalytic mechanism underscores that ZnTiO3 coupling augments the generation of photogenerated charge carriers. Nonetheless, concurrently, it undermines the crystalline integrity of the composite, yielding an excess of amorphous constituents that impede the mobility of photoinduced carriers. This dual effect also fosters escalated recombination of photogenerated charges, culminating in diminished quantum efficiency and reduced photocatalytic performance.

Visible light active Ti3+ self-doped mesoporous TiO2 photocatalyst with efficient photocatalytic performance for the degradation of chlorpyrifos

ABSTRACT In the present research, Ti3+ self-doped TiO2 photocatalyst (Ti3+-TiO2) was fabricated through a facial in-situ NaBH4 reduction approach. The as-prepared Ti3+-TiO2 were characterised using FESEM-EDS, TEM, HRTEM, XRD, UV-DRS, PL, EIS, and BET methods. The photocatalytic performance of the Ti3+-TiO2 was assessed through the degradation of chlorpyrifos (CPY) as an organophosphorus pesticide under visible LED light irradiation. The Ti3+-TiO2 exhibited excellent photocatalytic degradation efficiency at initial CIP concentration = 1 mg L−1, pH = 7, catalyst dosage = 0.2 g L−1, and reaction time of 50 min with 97%, which is 4.62 times higher than that of pristine TiO2. The extraordinarily boosted photocatalytic activity of Ti3+-TiO2 can be attributed to mesoporous nanostructure, oxygen vacancy, and Ti3+ self-doping, which facilitates visible light harvesting and accelerates charge carrier separation and transport. In addition, Ti3+-TiO2 shows outstanding mineralisation capability and recycling performance in degrading CPY. Coexisting water anions (NO3 −, Cl−, SO4 2-, HCO3 −) and HA inhibited the degradation of CPY. Their inhibition effects of selected anions followed the order of HCO3 − > SO4 2-> NO3 − > Cl−. Besides, a possible reaction mechanism of the photocatalytic process was recommended based on evidence from the radical scavenging test and photoelectrochemical measurements. The energy consumption value in this study was much less than that reported in other studies. Collectively, the findings show that Ti3+-TiO2 photocatalyst has tremendous potential in solar photocatalytic degradation of refractory organic pollutants.

N-TiO2/FeMIL-88B- A Promising Photocatalyst for Photoconversion of CO2 into Methanol

The present objective of this work is to find photoactive materials capable of facilitating visible light-driven redox reactions between CO2 and H2O. Our research is primarily focused on the incorporation of nitrogen (N) into the crystal lattice of titanium dioxide (TiO2) and its deposition onto Fe-MIL-88B to improve light absorption properties, minimize recombination of photo-generated electron-hole pairs, and increase CO2 adsorption capacity. The N-TiO2/Fe-MIL-88B composite was successfully prepared and characterized using SEM, XRD, and EDX techniques. The introduction of N-TiO2 into Fe-MIL-88B does not damage the crystal structure of Fe-MIL-88B. Anatase is the only crystalline phase observed from the XRD diffraction pattern. SEM images show that N-TiO2 is well dispersed on the Fe-MIL-88B surface. The results of quantum simulations indicate that TiO2 strongly interacts with Fe-MIL-88B. The binding energy is determined to be -78.2 kcal/mol. The calculated UV-Vis results revealed that the light absorption edge of the TiO2/Fe-MIL-88B was red-shifted in comparison with that of the pure TiO2 (from ca. 500 nm to 550 nm). The red-shifted light absorption of TiO2/FeMIL-88B suggests that the band gap of TiO2/Fe-MIL-88B is narrower compared to that of the pristine TiO2, indicating the better light utilization ability of the TiO2/Fe-MIL-88B. Results from high-performance liquid chromatography show that N-TiO2 has the capability to convert CO2, but at a significantly low rate. The methanol formation is distinctly observed only over the N-TiO2/Fe-MIL-88B catalyst. The CO2 conversion efficiency, estimated using gas chromatography, is calculated to be 11.94%.

Surface diffusion induced degradation enhancement and zero-order kinetics in edge-connected MoS2/Au/TiO2 Z-scheme photocatalytic system

Heterostructured photocatalysts have demonstrated great potential in the photodegradation of organic pollutants, while the surfaces & interfaces of their multiple structural components play critical roles in determining their photocatalytic mechanisms and kinetics. Here, we fabricate an edge-connected MoS2/Au/TiO2 photocatalytic system via a selective photodeposition method and utilize a surface-diffusion mechanism to maximize the synergistic effects among the components. The resultant photocatalytic system behaves as a Z-scheme with well spatially separated redox reaction sites. The optimal catalyst 10 % MS/Au/T exhibited a pseudo 1st-order rate constant of 0.0145 min−1 within 120 min, which is seven times more than that of pristine TiO2. The edge-deposited MoS2 in the nanocomposite serves as a reservoir to adsorb and then transport the pollutant molecules rapidly to TiO2 surface for oxidation. Such a pre-concentration effect, as well as the Z-scheme charge transfer mechanism, has enhanced the overall degradation efficiency, and induced the occurrence of zero-order degradation kinetics. The charge transfer behaviors, the diffusion-enhancement mechanism, zero-order kinetics, and the order transition are then thoroughly studied against the MoS2 mass loading. 10 % MS/Au/T showed the highest values of zero and first-order constants, which were 0.073 ppm/min and 0.011 min−1, respectively. A diffusion-enhanced model is developed and validated to explain the experimental observations. This work provides meaningful insights into degradation enhancement and kinetic analysis for heterostructured photocatalytic systems.

Facile synthesis of reduced graphene oxide and graphitic carbon nitride modified titanium dioxide nanospheres for photoanode of dye-sensitized solar cell

Titanium dioxide/reduced graphene oxide nanocomposites (TiO2/rGO NCs) have been broadly utilized as photoanode materials for dye-sensitized solar cell (DSSC). Nevertheless, photoelectric conversion efficiency (PCE) of DSSC is diminished due to recombination of charges takes place between photoanode and electrolyte interface. Herein, we have prepared a triplet structure nanocomposite composed of TiO2 nanospheres, rGO and graphitic carbon nitride (TiO2 NS/rGO/g-C3N4 NC) for photoanode of DSSC. The ternary TiO2 NS/rGO/g-C3N4 NC photoanode has enhanced dye absorption considerably and as a consequence, improved light harvesting efficiency. Besides, the introduction of rGO and g-C3N4 on the TiO2 NS has effectually speeded up the transport of electrons and minimized the recombination of photogenerated charges. Consequently, the DSSC integrated with ternary TiO2 NS/rGO/g-C3N4 NC photoanode has exhibited ∼41 % increment in the PCE of 5.77 % when compared to PCE of the pristine TiO2 NS photoanode (4.10 %). This finding has proposed a simplistic approach to advance photovoltaic performance of the DSSC.

Photodegradation of Methyl violet using Ag modified TiO2 nanotubes by UV and UV/ H2O2

Titanium dioxide (TiO2) is a semiconductor material that is frequently utilized in photodegradation applications. Its application in photodegradation is constrained by its broad band gap of 3.2 eV and increased rate of photoelectron recombination. However, by doping TiO2 with metallic nanoparticles, the band gap can be modified and photodegradation can be improved. The present study explores the fabrication of Ag-modified TiO2 nanotube photocatalysts by electrochemical anodization followed by hydrothermal method. The structural, morphological, compositional, optical, and thermal properties of prepared photocatalysts were characterized by X-ray analysis, Field emission scanning electron microscopy, N2 adsorption desorption analysis, X-ray photoelectron spectroscopy, Energy dispersive X-ray spectroscopy, UV–Vis diffuse reflectance analysis and Thermogravimetric-differential thermal analysis. The prepared photocatalyst was utilized to investigate the degradation of methyl violet in the presence of UVA and UVC radiation. The effects of UVA and UVC illumination on the degradation process, the effect of Ag loading in the TiO2 nanotube arrays and the role of H2O2 in the degradation of pollutant were studied. The degradation efficiency of methyl violet in the presence of UVC light was three times that of UVA light. For pristine TiO2 photocatalyst, the maximum degradation of 70% was obtained under UVC illumination in 8 h. When H2O2 was added, complete degradation was observed within 3 h. Reusability studies have shown that photocatalysts are stable and can be used for the degradation of methyl violet.

Degradation of multiple xanthates using highly efficient visible light-responsive BiOBr-TiO2 composite photocatalysts

BiOBr-TiO2 (BT) composite photocatalysts were synthesized by using a two-step method including hydrothermal synthesis and water-bath precipitation. The microstructural characterization analysis proved that high-crystallinity and high-purity binary BT materials were achieved without by-products. TiO2 nanoparticles with a diameter of approximately 15 nm were decorated on multi-layered BiOBr nanosheets. The results showed that BT had highly-improved adsorption capacity and photocatalytic efficiency in comparison to pristine BiOBr and TiO2. The reaction rate constant of the optimal BT-2 composite photocatalysts for the degradation of 20 mg/L sodium ethyl-xanthate could reach 0.06496 min−1, which was 2.7 and 40.3 times than pure BiOBr and TiO2, respectively. The free radical scavenger test demonstrated that photogenerated holes were the main active species in the photocatalytic degradation reaction process. A possible degradation pathway for SEX molecules was provided through the interaction of visible light and BT-2 photocatalyst. The as-prepared BT materials can be used as efficient photocatalysts to completely degrade various types of xanthates under visible light.