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•TiO2/TiO2–GO thin films were deposited using spray pyrolysis and sol–gel spraying.•The surface roughness significantly influences the photocatalytic efficiency.•Composite’s ...VIS-activation is more significant at a higher GO content (1.4 vs. 0.25%).•The composites were stable during photocatalysis, with no film wash-out.
This paper reports on a novel path to deposit VIS-active composite photocatalytic thin films based on titanium dioxide (TiO2) and graphene oxide (GO) by coupling two up-scalable techniques: spray pyrolysis deposition (SPD) and sol–gel spraying (SG). The first step involves the SPD deposition of aTiO2layer on the FTO substrate, followed by the deposition of a TiO2-GO composite layer from adispersion and the influence of the GO content on the stability, morphology and crystallinity of the two-layered thin film was outlined. The thin films were tested in standard photo-degradation processes, using the methylene blue (MB) dye andimidacloprid (IMD) to outline the effect of a possible dye-sensitization, under simulated solar radiation, UV (~5%) + VIS (~95%), at low irradiance values. Comparative experiments using only UV radiation proved the extension of the activation domain towards VIS as result of the GO insertion in the composite thin films. The thin films proprieties were investigated correlated with the MB and IMD photo-degradation;the results show that the photocatalytic efficiencies were mainly influenced by the composites roughness (specific surface) and crystallinity. The stability of the thin films in the aqueous pollutant environment was good as the experimental results showed no wash-out effect.
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•The composite photocatalyst B-TiO2-xGO was prepared by sol–gel and calcination methods.•2D honeycomb GO improve the separation of the photogenerated charge carriers and absorption of ...H2O2.•Photo-activity of B-TiO2-3GOwas 1.5-fold for NO removal than bare B-TiO2.•The synergy between oxygen vacancies and graphene oxide was explored and demonstrated in detail.
It is important to find an effective way to enhance the photocatalytic NO removal efficiency of black-TiO2. In this work, we used a simple hydrothermal method to synthesize the black TiO2-GO composite. One of the black TiO2-GO composites, B-TiO2-3GO (black TiO2-GO composites with graphene content of 3 wt%), exhibits remarkably high activity toward the photocatalytic removal of NO, with a NO conversion rate of 50.4% which is greater than that of pure black TiO2 (33.9%). The experimental results revealed that the TiO2-GO nanocomposite photocatalyst has the high absorption ability from large surface area and well mobility of charge carriers, which can enhance its photocatalytic activity. What’s more, the UV–vis (DRS)spectra, XPS and NO-TPD-MS indicated that the synergy between H2O2, oxygen vacancies and GO. Finally, a possible photocatalytic NO removal mechanism over the B-TiO2-GO composite is also presented based on the results of the band structures, the free radical capture experiments and electron spin resonance (ESR) tests. This work would provide a strategy to design HNO3/H2O2-resistant deNOx photocatalyst in the pollutant purification field.
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•Six GO-TiO2 composites were synthesized and characterized.•The GO content affects the degradation kinetics.•Photocatalytic treatment in a leachate reduces the photodegradation ...rate.•Forty-six intermediates were detected during treatment.•Different transformation routes can be followed in different matrices.•The cyclopropyl ring remains in most cases the main site of reaction.
The photocatalytic treatment of the antiviral drug abacavir has been studied using graphene oxide (GO)-titania (TiO2) nanocomposites as catalysts under simulated solar irradiation. A mild ultrasonically assisted synthetic route was followed for the preparation of the GO-TiO2 composites. Their characterization and determination of their physicochemical properties was conducted employing Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), BET analysis and X-ray Diffraction (XRD). Six different nanocomposites were tested towards their photocatalytic efficiency containing a varying amount of GO ranging from 1 % to 20 %. The degradation kinetics followed the first-order kinetic law. The synthesized composite with 2 % GO appeared to be the most effective achieving complete disappearance of the target compound within 20 min. The photocatalytic degradation of the target compound proceeded in slower rates when using a landfill leachate as a water matrix due to its increased complexity. The identification of the transformation products (TPs) revealed the formation of forty-six intermediates arising from different transformation routes. The cyclopropyl ring appears to be the main site of reaction although hydroxylation, dehydrogenation, deamination/hydroxylation and isomerization of the parent compound may be also observed. The evolution profiles of the most abundant TPs in the two matrices (ultrapure water and leachate) revealed that different transformation routes may be more favored in each matrix.
The present study reports a novel, simple, economic and ecofriendly method to synthesize Titanium dioxide (TiO2) nanoparticles using green alga Chlorella pyrenoidosa. Further, these TiO2 ...nanoparticles were deposited on GO sheets to form TiO2-GO nanocomposite. The crystalline information, morphological and optical properties of the synthesized TiO2-GO nanocomposite were studied using X-ray Diffraction (XRD), Scanning Electron Microscopy- Energy Dispersive X-ray Spectroscopy (SEM-EDX) and UV–Vis absorption spectroscopy. Crystal Violet (CV) dye was used as a model contaminant. The photocatalytic activity of TiO2 nanoparticles and the TiO2-GO nanocomposite were evaluated by the degradation of CV dye in aqueous medium under visible light. The result showed that the TiO2-GO nanocomposite exhibited higher photocatalytic efficiency compared to pristine TiO2 nanoparticles with three cycles reusability. The improved activity of the TiO2-GO nanocomposite might be attributed to enhanced charge separation, efficient charge transportation, extended light absorption range and increased adsorption of dye. This nanocomposite has a great potential in removing environmental contaminants and applicable in water purification.
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•TiO2 nanoparticles were synthesized using green algae.•Anatase TiO2 nanoparticles were deposited on GO sheets by hydrothermal approach.•Photocatalytic activity of TiO2 and TiO2-GO photocatalyst was evaluated on crystal violet dye under visible light.•TiO2-GO showed higher photocatalytic activity compared to TiO2 nanoparticles.
Simple sol-gel method and microwave method were used to prepare two-dimensional Pd1Snx/TiO2-GO catalyst with high catalytic activity and strong resistance to CO poisoning. The morphology and ...structure of Pd1Snx/TiO2-GO catalyst were characterized by TEM, XRD and XPS. It was shown that the spindle TiO2 are uniformly fixed on the GO sheets and can still maintain the morphology after Pd and Sn nanoparticles loading. At the same time, Pd and Sn NPs were both uniformly anchored on the surface of the composite carrier according to EDS element mapping. The two-dimensional composite support TiO2-GO formed by the spindle-shaped TiO2 grown uniformly in-situ on GO helps to achieve uniform anchoring of metal nanoparticles. By introducing the second metal Sn, the electronic structure of Pd can be modified to provide more oxygen-containing groups, which leads to a more complete ethanol oxidation process. Through electrochemical tests, it can be found that Pd1Snx/TiO2-GO had excellent catalytic activity, anti-poisoning ability and long-term stability for ethanol electrooxidation in alkaline environment. The residual current density of Pd1Sn0.40/TiO2-GO is 7 times than that of PdSn/C (JM). Especially, the residual current density of Pd1Sn0.40/TiO2-GO catalyst only decreased by 16.7% after continuously scanned by cyclic voltammetry for 8 times.
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•Two-dimensional support enhanced the anti-poison ability to CO of Pd1Snx/TiO2-GO.•The interface effect of Pd and TiO2 enhanced resistance to CO poisoning of catalyst.•TiO2-GO composite support resulted in excellent stability of Pd1Snx/TiO2-GO.•The residual current density of Pd1Sn0.40/TiO2-GO is 7 times that of PdSn/C (JM).
•TiO2NTs-GO/NH2/Ag nanocomposite was prepared by a facile method.•The nanocomposite owns large surface area of 137 m2/g and high dye sorption ability.•New nanocomposite based photoanode shows ...photoconversion efficiency of 8.18%.•Amine functionalization and Ag NPs incorporation synergistically reduce RCT.•Ag0 and –NH2 incorporation in TiO2 NTs-GO effectively increase the e- transport.
In dye-sensitized solar cell (DSSC), the semiconductor photoanode plays a vital role in gathering photo-excited electrons from the sensitizer. Generally, the photoconversion efficiency of photoanode is hampered by electron-hole recombination. To circumvent this, modification of TiO2 nanotubes with amine functionalized graphene oxide (GO) has been attempted.
Nanocomposites consisting of ethylenediamine functionalized graphene oxide (GO/NH2) and titania nanotubes (TiO2 NTs) are prepared by hydrothermal method and are incorporated with 3 wt% of Ag nanoparticles. The nanocomposites are studied using diffuse reflectance spectroscopy, Raman spectroscopy, XRD, TEM and XPS techniques.
The GO surface acquire defect structure and disorder after amine functionalization which occurs via reactive oxygen groups to form C−N bond. The nano-silver incorporated amine functionalized GO modified TiO2 nanotubes (TiO2 NTs-GO/NH2/Ag) exhibit high dye adsorption capacity and leads to more light gathering. The DSSC fabricated with TiO2 NTs-GO/NH2/Ag photoanode exhibits very good photo-conversion efficiency (8.18%). Significant light-to-electrical energy conversion efficiency of the TiO2 NTs-GO/NH2/Ag photoanode DSSC is due to the efficient charge transport at the interfaces, high dye loading and broad absorption by the sensitizer adsorbed TiO2 NTs-GO/NH2/Ag thin-film.
Possible mechanism of electron transport in TiO2 NTs-GO/NH2/Ag photoanode. Display omitted
•Nano TiO2-graphene oxide (TiO2-GO) photocatalysts were developed.•TiO2-GO catalysed photodegradation of Polystyrene (PS) was studied under UV light.•PS-TiO2-GO composites underwent accelerate ...photo-oxidative degradation.•Formation of charge centers were observed in UV irradiated PS composites.•Photodegradation lead to deterioration in mechanical and thermal properties of PS.
Nano TiO2-graphene oxide (TiO2-GO) composites with varying weight percentages of GO were successfully developed by ultrasonication assisted hydrothermal approach and characterised. HRTEM analysis revealed that the GO sheets associated with TiO2 have broken down into nano dimensions. Photodegradation of polystyrene (PS), PS-TiO2 and PS-TiO2-GO composites were studied under UV irradiation of wavelength 253 nm. Nano TiO2-GO loaded solid phase polystyrene (PS) underwent an accelerated photodegradation compared to Pristine PS and PS-TiO2 composite as evident from various monitoring techniques. Gel permeation chromatography (GPC) revealed that the degradation proceeded through random chain scissions decreasing the average molecular weights. PS and PS composites followed the mechanism of photo oxidative degradation as evident from FTIR. Maximum degradation percentage was observed in PS-TiO2-30%GO compared to the other specimens under study. Mechanical properties including tensile and flexural strengths which were found to be higher for the PS composites compared to pristine PS, decreased appreciably upon UV irradiation due to deterioration of polymer chain. Dielectric strength of the PS composites also decreased as a consequence of photodegradation revealing the formation of charge centers within the polymer chain. Dielectric permittivity of the polymer specimens under study increased upon UV irradiation suggesting the formation of more polar centers. The improved thermal stability of PS composites compared to pristine PS decreased due to photodegradation of the polymer chain. The glass transition temperature (Tg) and decomposition temperature lowered as a consequence of chain scission of polymer specimens caused by photodegradation. Photocatalytic activity of nano TiO2 was enhanced upon its surface modification using GO for the photodegradation of PS under UV radiation.
A ternary nanocomposite material based on TiO 2 , graphene oxide and core-shell nanostructures of Ag/TiO2 composition was obtained by a two-step hydrothermal method. The formation of a dual TiO2-GO ...nanocomposite was confirmed by Raman spectroscopy data, where the nanocomposite spec- tra contain peaks characteristic of both TiO 2 and graphene oxide. Studies of electrophysical character- istics have shown that the addition of plasmon nanoparticles leads to an improvement in the charge-transfer characteristics of the synthesized material. This is due to the fact that the charge transfer resistance of a ternary nanocomposite material TiO2-GO-Ag is noticeably lower than for pure TiO 2 ( 13 times) and TiO2-GO nanocomposite ( 3 times). In addition, the prescence of Ag/TiO2 core-shell nanostructures in the TiO2-GO nanocomposite material leads to an increase in the efficiency of conversion of incident light into photocurrent, which will be resulted in the growth of photocatalytic activity of synthesized materials.
•TiO2-GO thin films were deposited onto glass substrates by spin coating technique at various coating speeds.•All deposited films showed an amorphous homogeneous, and smooth structure with very small ...surface roughness.•These films showed thinner layers and lower bandgap energies with higher spin coating speeds.•The transmittance level of the films was decreased at high spin coating speeds.•TiO2-GO thin films may be good candidates for transparent oxide conductive electrodes useful in solar cells.
Nanostructured titanium dioxide–graphene oxide (TiO2-GO) thin films have been successfully synthesized and deposited on glass substrates using spin coating technique. TiO2-GO nanocomposites were prepared using Titanium Tetra Isopropoxide (TIP) and Graphene Oxide (GO) nanosheets. The influences of spin coating deposition speed on the structural, morphological, and optical features of the resulting TiO2-GO samples have been investigated. X-ray diffraction (XRD) patterns showed an amorphous structure of all deposited films. Scanning electron microscopy (SEM) images demonstrated that these films are homogeneous and all free from cracking over the entire surface of the sample, regardless of the number of rotations used. Atomic force microscopy (AFM) topography images reveal that all samples are smooth with very small surface roughness. Optical data obtained from UV–Vis spectrophotometer measurement together with theoretical modeling using Tauc–Lorentz (TL) oscillator model showed that all films display high transmittance level around 85% from the visible to the near-infrared region. It is also shown that an increase in spin coating speed results in a decrease in the film thickness and the optical band gap. The observed optical features reveal that TiO2-GO thin films are promising candidate that can be used as transparent conducting oxide electrode in solar cells.
•Phthalates concentrations of DEP, DBP, BBP and DEHP in the mixed industrial effluent of CETP exceeding by 10 folds than the literature values.•The removal efficiency of CETP based on pure biological ...treatment, was 77.9%, 32.8%, 97.5% and 41.8% for DEP, DBP, BBP, and DEHP respectively.•During photolysis and photo-catalysis of DEHP by UV and UV-TiO2-GO, maximum removal of DEHP was achieved at pH 6.•Various oxidative and ring opening by products by the oxidation and de-esterification by O2− and Hydroxyl radicals (OH−.) were detected by GC–MS in photocatalytic reaction.
The occurrence and effectiveness of common effluent treatment plants (CETPs) for the removal of phthalates, as well as the fate of DEHP, are demonstrated in this study using a nano TiO2-Graphene-based photo-catalyst and photolytic system. Full-scale CETPs were selected at SIDCUL, Haridwar, and Unnao, Uttar Pradesh, along with installing a lab-scale photocatalytic reactor. Solid phase extraction (SPE) and gas chromatography-mass spectrometry (GCMS) was used to extract and quantify four phthalates, namely DEP, DBP, BBP, and DEHP, and byproducts.
The average concentration of DEP, DBP, BBP, and DEHP in the mixed industrial effluent of CETP Haridwar exceeded by around ten folds than the literature value. Still, it was removed significantly by 77.9%, 32.8%, 97.5%, and 41.8%, respectively.
The average influent concentration was eventually lower than the treated effluent at CETP Unnao, and phthalates were not removed during the process. During process optimization, the distinct ability of each method to remove DEHP during photolysis and photo-catalysis was discovered. The UV-TiO2-GO had removal effectiveness of 98% in 30 min at pH-6. However, at a dose of 500 mg, UV and UV-TiO2-GO had removal efficacy of 73% and 86%, respectively, for 180 min. After de-esterification, the UV system only cleaved the aliphatic chain, leaving the aromatic ring intact and producing a variety of byproducts. The superoxide ions (O2°−) and hydroxyl radicals produced in the photocatalytic process attacked not only the aliphatic chain but also the benzene ring.
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