TiO2 Network Research Articles

Solar-driven chloride activation via 3D oxygen-vacancy-rich TiO2 network photoanode for ultrafast and durable purification of saline wastewater

Photoelectrochemical chloride activation (PEC-Cl) is a promising and reagent-free strategy to treat saline organic wastewater by activation of chloride (Cl–) using sunlight. However, the low efficiency and Cl– corrosion of photoelectrode, and the limited mass transfer of pollutant hinder its application. Herein we successfully solve these challenges by developing porous oxygen-vacancy-rich TiO2 nanoneedle arrays (TiO2 NNs-r400) photoanode. Under illumination, the photoinduced holes in TiO2 NNs-r400 oxidize Cl– to reactive species (e.g., HOCl, Cl•, Cl2•− and ClO•), resulting in the degradation rate of tetracycline hydrochloride (HTC, 0.861 min−1) by TiO2 NNs-r400/PEC-Cl system is 2–3 orders of magnitude higher than the state-of-the-art. Experiments and computational analysis indicate that oxygen vacancies (Ovs) on TiO2 NNs-r400 promote the photocarriers separation efficiency and more importantly, facilitate Cl– adsorption with intermediary strength and reduce the energy barriers of Cl– oxidation. Furthermore, we design a continuous flow-through PEC reactor for TiO2 NNs-r400/PEC-Cl technology. The process exhibits 100% HTC degradation (TOC = 60.23%) for over 2000 h flow-through operation, which maintains high activity in the treatment marine aquaculture wastewater with nearly zero energy consumption by directly utilize natural sunlight. In the final effluent, the toxicity of almost all degradation intermediates is decreased, and the formation of total organic chlorine is low (17.2 µg L–1). This work provides insights into Cl– activation on Ov-rich photoanode and strategy for practical application of solar energy in efficient, sustainable and eco-friendly wastewater decontamination.

3D network of MnTiO3–TiO2 eutectic composite studied by Raman spectroscopy

A MnTiO3–TiO2 eutectic composite grown by the micro-pulling down method was studied by Raman spectroscopy. The Raman investigation confirmed that this eutectic consists of the three-dimensional network of TiO2 elongated precipitates interconnected by thin TiO2 lamellas embedded in a MnTiO3 matrix. Raman scattering spectra revealed that the TiO2 phase crystallizes in the rutile structure and the MnTiO3 matrix in the ilmenite structure. The thin lamella regions combine both the TiO2 and MnTiO3 phases. Two Raman lines at 116 cm−1 and 136 cm−1 not observed in a perfect ilmenite single crystal but observed for the eutectic MnTiO3 phase can be used to derive information about deviations in the MnTiO3 structure.

The impact of a TiO2/r-GO composite material on the performance of electron transport electrodes of dye sensitized solar cells.

In dye sensitized solar cells, the role of the electron transport layer is crucial because it makes it easier for photo-generated electrons to get from the dye to the external circuit. In DSSCs, the utilization of TiO2 is likely to be given preference in the production of electron transport electrodes due to its notable characteristics such as its expansive surface area, porosity, and capacity to scatter light. Nevertheless, the presence of heterogeneity within the mesoporous structure increases the likelihood of TiO2 aggregation, which subsequently diminishes the beneficial impact of TiO2 on the performance of DSSCs. In this context, reduced graphene oxide (r-GO) is introduced as an additive into the TiO2 network during the preparation of TiO2/reduced graphene oxide (r-GO) composites. The integration of r-GO with TiO2 has been recognized as a promising approach to enhance electron transport and electron lifespan, owing to remarkable qualities exhibited by r-GO. The present investigation involved the synthesis of a composite material including titanium dioxide/reduced graphene oxide (TiO2/r-GO) through the utilization of the co-precipitation technique. Following this, the generated TiO2/r-GO composite material and pure TiO2 were deposited on FTO through electrophoretic deposition to obtain an electron transport electrode of a dye sensitized solar cell. It should be noted that when r-GO was combined with TiO2, the performance of DSSCs improved notably compared to pure TiO2. As a result, the findings of this work have significant implications for the advancement of the TiO2/r-GO composite deposited through electrophoretic deposition. The power conversion efficiency reached 6.64% with the addition of r-GO in the metal oxide electron transport electrode. The obtained findings align with the outcomes of electrochemical impedance investigations in which the electrode constructed with TiO2/r-GO exhibits reduced electron transport resistance (RCt) at the anode/dye/electrolyte interface, as well as lower overall resistance (Rtotal) in comparison to TiO2-based DSSCs. These advancements have the potential to be employed in commercial DSSC manufacturing.

Color adjustable, mechanically robust, flame-retardant and weather-resistant TiO2/MMT/CNF hierarchical nanocomposite coatings toward intelligent fire cyclic warning and protection

Fire safety and protection are very important but still show a critical global challenge. Developing smart fire warning materials with combined passive flame retardancy and active fire alarm response is promising for reducing or avoiding serious fire disasters. Various nano-fillers (e.g., graphene oxide and MXene) based composite coatings have proven to be effective for monitoring critical fire risk of various combustible materials; however, they still show some shortages, for example, high cost, black color, poor weather resistance and complicated fabricating process. Here, we report a green, cost-effective and large-scale strategy for fabricating water-based 3D-titania/2D-montmorillonite/1D-celluose nanofiber (TiO2/MMT/CNF) hierarchical nanocomposite coatings with adjustable color, mechanical robustness, good flame retardancy, long-term weather resistance and sensitive fire cyclic alarming response. The formation of strong chemical bonding and hydrogen bonding interactions among polyethylene glycol molecules and multi-scale nano-fillers together with silane surface modification can produce good mechanical flexibility (folded crane), surface hydrophobicity (water contact angle of 152°) and exceptional flame resistance (good structure integrity after 120 s flame exposure). Notably, the optimized nanocomposite coatings exhibit ultrafast fire alarm response (<3.5 s) and stable fire cyclic alarming capability via the possible band transition of the TiO2 network under flame. Further, such color-adjustable nanocomposite coatings can be easily fabricated for large-scale production, and they show excellent stable flame retardancy and stable fire cyclic warning response even after more than one-year outdoor exposure. This work provides a promising and green fire-warning nanocomposite coatings with combined passive-active functionalities for fire warning and protection.

Nanoheterojunctions MnCo2O4 nanoparticles anchored on mesoporous TiO2 networks for superior photocatalytic ability

Antibiotics have been observed in industrial and domestic wastewater due to the extensive utilization of pharmaceuticals, demonstrating a considerable threat to aquatic ecosystems and human health. In this research, novel MnCo2O4 nanoparticles (NPs) accommodated on porous TiO2 networks were prepared by sol-gel approach for tetracycline (TC) degradation. TEM images revealed that the MnCo2O4 NPs (5–10 nm) was accommodated on mesoporous anatase TiO2 (20–30 nm). The 3% MnCo2O4/TiO2 photocatalyst displayed the maximum photocatalytic ability among the synthesized samples, including commercial P-25 and pristine TiO2, which indicated a high photocatalytic activity of 100% within 60 min of illumination time. The rate constants (k) values revealed that 3%MnCo2O4/TiO2 nanocomposite was 0.0479 min−1, which was about 18.4 and 47.9 folds greater than that of TiO2 NPs and P-25. The increased photocatalytic performance of MnCo2O4/TiO2 was ascribed to extending visible light response and promoting separation rate of electron-hole. Additionally, the unique mesostructured with the high surface area provided an abundant active site and outstandingly reduced MnCo2O4 aggregation. Meanwhile, the synthesized 3%MnCo2O4/TiO2 photocatalyst displayed excellent stability after five cycles. The photocatalytic mechanism over the heterojunction MnCo2O4/TiO2 nanocomposites was addressed in detail. The obtained mesostructure photocatalyst with a large surface area through this reasonable procedure strategy can significantly degrade and mineralize the organic contaminants in industrial and domestic wastewater under visible light.

Synergistic enhanced Zinc-ion battery performance achieving by atomic layer deposition of TiO2 on three-dimensional carbon nanotube network decorated Zn anode

Herein, we report a unique synergistic effect between carbon nanotube (CNT) network and atomic layer deposition (ALD) of TiO2, which not only enhances the ability to capture zinc ions but also suppresses Zn dendrite growth, resulting in uniform deposition of zinc ions during repeated cycles. The CNTs with luxuriant three-dimensional skeleton structure can provide plentiful deposition sites on Zn metal anode, which significantly reduces the nucleation overpotential and improves the reaction kinetics. Meanwhile, the TiO2 can repeatedly guide the uniform deposition of Zn owing to the excellent zincophilic. The deposition mechanism of zinc in the modified anode (TiO2CNT@Zn anode) is fully explained by comparing different carbon materials. The TiO2CNT@Zn anode shows a high Zn plating/stripping reversibility with an ultralow nucleation overpotential and achieves an ultralong lifespan over 2000 h with a voltage hysteresis of 22.5 mV compared to bare zinc (BZ) anode (63.7 mV) at a high current density of 5 mA cm−2. Moreover, the TiO2CNT@Zn anode maintains a highly stable Coulombic efficiency of 98.9% for more than 500 h. Moreover, the Zn-MnO2 battery with the TiO2CNT@Zn anode shows remarkably enhanced cycling stability.

Durable self-cleaning nano-titanium dioxide superhydrophilic coating with anti-fog property

PurposeThis paper aims to design the nano-titanium dioxide (TiO2) coating system which has superhydrophilic property, self-cleaning mechanism and antifog property as well as strong adhesion on glass substrate.Design/methodology/approachTwo hydrophilic materials have been used such as TiO2 nanoparticles as fillers and hydrophilic copolymer, Pluronic F-127 by using simple sol–gel approach. The prepared solution was applied onto glass through dip- and spray-coating techniques and then left for drying at ambient temperature.FindingsThe nano-TiO2 superhydrophilic coating has achieved the water contact angle of 4.9° ± 0.5°. The superhydrophilic coating showed great self-cleaning effect against concentrated syrup and methylene blue where thin layer of water washes the dirt contaminants away. The nano-TiO2 coating exhibits great antifog performance that maintains high transparency of around 89% when the coated glass is placed above hot-fog vapor for 10 min. The fog droplets were condensed into water film which allowed the transmission of light through the glass. The strong adhesion of coated glass shows no total failure at scratch profile when impacted with scratch load of 500, 800 and 1,200 mN.Research limitations/implicationsFindings will be useful in the development of self-cleaning superhydrophilic coating that is applicable on building glass and photovoltaic panel.Practical implicationsThe developed nano-TiO2 coating is developed by the combination of hydrophilic organic copolymer–inorganic TiO2 network to achieve great superhydrophilic property, optimum self-cleaning ability and supreme antifog performance.Social implicationsThe findings will be useful for residents in building glass window where the application will reduce dust accumulation and keep the glass clean for longer period.Originality/valueThe synthesis of nano-TiO2 superhydrophilic coating which can be sprayed on large glass panel and cured at ambient temperature.

Investigation on the effect of neodymium ion doping in TiO2 on the photovoltaic performance of dye-sensitized solar cells

Titanium dioxide (TiO2), neodymium (Nd3+) doped TiO2 with the doping levels of 0.3% and 0.5% were synthesised by hydrothermal method and were characterized by powder X-ray diffraction (XRD), UV–vis diffused reflectance spectroscopy (DRS), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Ultraviolet X-ray photoelectron spectroscopy (UPS) and high resolution transmission electron microscopy (HRTEM). Doping of Nd3+ ions have been created new surface energy states below the conduction band of TiO2 which mediate the photoinjected electrons through TiO2 network to external load without any impediment. The Fermilevel (Ef) of TiO2 was shifted to downward direction upon Nd3+ ion doping confirmed from UPS analysis. An enhanced photoconversion efficiency (PCE) of 10.7% was achieved for the device fabricated using 0.3% Nd3+ ion doped TiO2 which is higher than that of the device with undoped TiO2 (10.1%). The noticeable increment in the PCE was due to the reduced charge recombination, longer electron lifetime and improved charge injection form LUMO of the N719 dye to the CB of TiO2.

Effect of Biogenic Silica Behavior in the Incorporation of Mesoporous Anatase TiO2 for Excellent Photocatalytic Mineralization of Sodium Diclofenac

TiO2/SiO2 composites were synthesized via a simple sol gel method by surface reduction of Ti4+ ions to Ti3+ using titanium isopropoxide as a TiO2 precursor and rice husks (RHA) as a SiO2 source. The silica content and calcination temperature of the materials were evaluated. Thermal, crystallographic and physicochemical aspects suggest that biogenic silica (SiO2) can improve the thermal stability of the anatase phase of TiO2, when the SiO2 content reaches 20%. The N2 adsorption-desorption isotherms showed that the SiO2-modified samples have uniform pore diameters and a large specific surface area. The XPS analysis showed the surface reduction of Ti4+ ions to Ti3+ within the TiO2 network via oxygen vacancies after SiO2 introduction, which is beneficial for the photocatalytic reaction. Photocatalytic degradation of sodium diclofenac (SDFC) shows that TiO2/SiO2 composites have better activity compared to commercial P25. Mesoporous TiO2 composite modified with 20 wt% SiO2 showed better photocatalytic mineralization than P25 (83.7% after 2 h instead of 57.3% for P25). The excellent photocatalytic mineralization of the photocatalysts can be attributed to the high anatase crystallinity exhibited by XRD analysis, high specific surface area, surface hydroxyl groups, and the creation of oxygen vacancy, as well as the presence of Ti3+ ions.

Investigation of Threshold Carrier Densities in the Optically Pumped Amplified Spontaneous Emission of Formamidinium Lead Bromide Perovskite Using Different Excitation Wavelengths

The high crystal quality of formamidium lead bromide perovskite (CH(NH2)2PbBr3 = FAPbBr3) was infiltrated in a mesoporous TiO2 network. Then, high-quality FAPbBr3 films were evaluated as active lasing media, and were irradiated with a picosecond pulsed laser to demonstrate amplified spontaneous emission (ASE), which is a better benchmark of its intrinsic suitability for gain applications. The behavior was investigated using two excitation wavelengths of 440 nm and 500 nm. Due to the wavelength-dependent absorbance spectrum and the presence of a surface adsorption layer that could be reduced using the shorter 440 nm wavelength, the ASE power dependence was strongly reliant on the excitation wavelength. The ASE state was achieved with a threshold energy density of ~200 µJ/cm2 under 440 nm excitation. Excitation at 500 nm, on the other hand, needed a higher threshold energy density of ~255 µJ/cm2. The ASE threshold carrier density, on the other hand, was expected to be ~4.5 × 1018 cm−3 for both excitations. A redshift of the ASE peak was detected as bandgap renormalization (BGR), and a BGR constant of ~5–7 × 10−9 eV cm was obtained.

PbI2-TiO2 Bulk Heterojunctions with Long-Range Ordering for X-ray Detectors.

High-performance X-ray detectors are usually based on single crystals, due to the long-range ordering and hence outstanding electronic properties. On the other hand, bulk heterojunctions (BHJs) that can effectively enhance photogenerated exciton dissociation are widely used for photodetectors. The benefits of both spur investigation into how to combine these two strategies to enhance X-ray detection. Here, TiO2 networks are incorporated into PbI2 crystals to form interpenetrating type II heterojunctions, namely BHJs. These BHJs exhibit long-range ordering in molecular packing similar to that of single crystals. Compared with single crystals, the long-range ordered BHJs facilitate the separation of photogenerated electrons and holes to inhibit recombination, extend the mobility lifetime product by 6.4 times, and consequently improve X-ray sensitivity by 5.8 times. Hence, this work provides a new strategy using gel-grown crystals to fabricate high-performance X-ray detectors as well as a new platform for studying the behavior of X-ray-generated carriers in BHJs with long-range ordering.

A Conductive Network and Dipole Field for Harnessing Photogenerated Charge Kinetics.

Photogenerated charge separation and directional transfer to active sites are pivotal steps in photocatalysis, which limit the efficiency of redox reactions. Here, a conductive network and dipole field are employed to harness photogenerated charge kinetics by using a Ti3 C2 /TiO2 network (TTN). The TTN exhibits a prolonged charge-carrier lifetime (1.026ns) and an 11.76-fold increase in hexavalent chromium photoreduction reaction kinetics compared to TiO2 nanoparticles (TiO2 NPs). This super photocatalytic performance is derived from the efficient photogenerated charge kinetics, which is steered by the conductive network and dipole field. The conductivity enhancement of the TiO2 network is achieved by continuous chemical bonds, which promotes electron-hole (e-h) separation. In addition, at the interface of Ti3 C2 and TiO2 , band bending induced by the dipole field promotes photogenerated electron spatially directed transfer to the catalytic sites on Ti3 C2 . This study demonstrates that a conductive network and dipole field offer a new concept to harness charge kinetics for photocatalysis.

Foldable high‐strength electrode enabled by nanosheet subunits for advanced sodium‐ion batteries

AbstractPower sources with strong mechanical properties and high‐energy density are highly desirable for the next‐generation flexible electronics. However, the challenge arises from the current electrode structure design, which is unable to bring both satisfactory mechanical and electrochemical properties with high active materials content and mass. Herein, we reported novel flexible, high‐strength, and mechanically stable TiO2‐based film electrodes for advanced sodium‐ion batteries, achieving an ultrahigh strength (up to ≈60 MPa) and commercial‐level areal capacity (4.5 mAh cm−2). Highly‐dispersed TiO2 and interlaced carbon nanotube (CNT) networks are embedded in the sheet‐liked cellulose to form porous, high‐conductive, and high‐active TiO2‐C nanosheets that is basic building subunits of TiO2‐C films, allowing the films with structural robustness and origami‐level flexibility. This strategy reconciles the contradiction between mechanical properties and active material content in flexible electrodes, and the fabricated electrode with a high TiO2 content of &gt;65% can be bent more than 11 000 times without breaking. Meanwhile, good capacity and excellent cycle stability (0.02‰ capacity‐decay rate over 9000 cycles) of TiO2‐C film under a higher active content (75%) has well satisfied the demands of flexible energy storage devices for electrochemical performances. This TiO2‐C subunit assembly methodology demonstrates enormous potential in high‐strength/toughness flexible electrode construction for flexible electronics.image

Visible-light harvesting innovative W6+/Yb3+/TiO2 materials as a green methodology photocatalyst for the photodegradation of pharmaceutical pollutants.

In this work, we report on the synthesis of a new-age reusable visible-light photocatalyst using a heterojunction nanocomposite of W6+/Yb3+ on a mixed-phase mesoporous network of monolithic TiO2. The structural properties of the monolithic photocatalysts are characterized using p-XRD, SEM-EDAX, TEM-SAED, XPS, PLS, UV-Vis-DRS, FT-IR, micro-Raman, TG-DTA, and N2 isotherm analysis. The electron microscopic analysis reveals a mesoporous network of ordered worm-like monolithic design, with a polycrystalline mixed-phase (anatase/rutile) TiO2 composite, as indicated by diffraction studies. The UV-Vis-DRS analysis reveals a redshift in the light absorption characteristics of the mixed-phase TiO2 monolith as a function of W6+/Yb3+ co-doping. It is observed that the use of (8.0mol%)W6+/0.4 (mole%)Yb3+ co-doped monolithic TiO2 photocatalyst, with an energy bandgap of 2.77eV demonstrates superior visible-light photocatalysis, which corroborates with the PLS studies in terms of voluminous e-/h+ pair formation. The practical application of the photocatalyst has been investigated through a time-dependent dissipation of enrofloxacin, a widely employed antimicrobial drug, and its degradation pathway has been monitored by LC-MS-ESI and TOC analysis. The impact of physio-chemical parameters such as solution pH, sensitizers, drug concentration, dopant/codopant stoichiometry, catalyst quantity, and light intensity has been comprehensively studied to monitor the process efficiency.

Prozac® photodegradation mediated by Mn-doped TiO2 nanoparticles: Evaluation of by-products and mechanisms proposal

TiO2 nanoparticles were efficiently doped with Mn applying microwave-assisted synthesis method. Anatase phase was confirmed by XRD pattern, which did not exhibit the peaks associated with MnOx contamination. Raman spectroscopy showed a displacement of up to 5 cm−1 in the O-Ti-O vibrational mode, suggesting that Ti was replaced by Mn. Oxidation state (Mn3+) was confirmed via high-resolution XPS spectrum of Mn 2p energy level. Incorporation of Mn into the TiO2 network resulted in increased surface area (64.6 m2 g−1), average particle size up to 16 nm, and bandgap reduction of up to 43 %. The photocatalytic properties of the materials were investigated through Prozac® degradation and improvement of up to 14 % (Ti-0.73 Mn) and 26 % (Ti-0.38 Mn) was seen on comparing doped TiO2 versus pure TiO2 during photocatalysis. Furthermore, after Prozac® photodegradation, TFMP was identified as the main by-product while MAEB and PPMA (other by-products) were seen to compete with each other in the degradation mechanism. In addition to the quantitative analysis done for Prozac®, TFMP, MAEB, and PPMA, LC MS-Q-TOF analysis was performed, confirming that in the presence of Mn-doped TiO2, specific by-products were formed, probably due to more oxidizing species being present in this reaction system. The present study has shown unprecedented evidence that the application of TiO2 nanoparticles efficiently doped with Mn promotes Prozac® degradation by specific mechanisms.

On the optical characterization and biological implications of titania phases

Abstract Transformation process of TiO2 from anatase to rutile phase upon annealing affects its optical and biological implications. In the present work; TiO2 is synthesized by sol-gel technique. The optical and biological implications were depicted through the transformation process covering the range of 350–800 °C. Raman spectroscopy applied for depicting the structural analysis. The absorption coefficient, optical band gap energies, extinction coefficient and color strength were calculated as a function of annealing temperature. Moreover, Biological implications were followed by immersion tests within DMEM for 72 h. The results showed variable changes in the optical parameter values upon annealing due to the induced structural changes in the TiO2 network. The biological implications proved successful formation of a new Ca–P depletion layer post 48 h immersion with priority for anatase. The results proved the apparent effect of annealing temperature on the structural, optical and biological activity. Therefore, TiO2 desired properties can be tailored.

Power of Aerogel Platforms to Explore Mesoscale Transport in Catalysis.

We describe the opportunity to deploy aerogels-an ultraporous nanoarchitecture with co-continuous networks of meso/macropores and covalently bonded nanoparticulates-as a platform to address the nature of the electronic, ionic, and mass transport that underlies catalytic activity. As a test case, we fabricated Au||TiO2 junctions in composite guest-host aerogels in which ∼5 nm Au nanoparticles are incorporated either directly into the anatase TiO2 network (Au "in" TiO2, AuIN-TiO2 aerogel) or deposited onto preformed TiO2 aerogel (Au "on" TiO2, AuON/TiO2 aerogel). The metal-meets-oxide nanoscale interphase as visualized by electron tomography feature extended three-dimensional (3D) interfaces, but AuIN-TiO2 aerogels impose a greater degree of Au contact with TiO2 particles than does the AuON/TiO2 form. Both aerogel variants enable transport of electrons over micrometer-scale distances across the TiO2 network to Au||TiO2 junctions, as evidenced by electron paramagnetic resonance (EPR) and ultrafast visible pump-IR probe time-resolved absorption spectroscopy. The siting of gold nanoparticles in the TiO2 network more effectively disperses trapped electrons. Density functional theory (DFT) calculations find that increased physical contact between Au and TiO2, induced by oxygen vacancies, produces increased hybridization of midgap states and quenches unpaired trapped electrons. We assign the apparent differences in electron-transport capabilities to a combination of the relatively better-wired Au||TiO2 junctions in AuIN-TiO2 aerogels, which have a greater capacity to dilute accumulated charge over a larger interfacial surface area, with an enhanced ability to discharge the accumulated electrons via catalytic reduction of adsorbed O2 to O2- at the interface. Solid-state 1H nuclear magnetic resonance experiments show that proton spin-lattice relaxation times and possibly proton diffusion are strongly coupled to Au||TiO2 interfacial design, likely through spin coupling of protons to unpaired electrons trapped at the TiO2 network. Taken together, our results show that Au||TiO2 interfacial design strongly impacts charge carrier (electron and proton) transport over mesoscale distances in catalytic aerogel architectures.

UV ‐aided graphene oxide reduction by TiO 2 towards TiO 2 /reduced graphene oxide composites for dye‐sensitized solar cells

Electron transport layer is one of the important layer in the dye-sensitized solar cells (DSSCs) which is responsible for the transport of photo-generated electrons by the dye to the outer circuit. TiO2 has been widely used as electron transport material in DSSCs. However, improving the electrical conductivity of TiO2 without sacrificing the surface area is one of the important strategies to improve the efficiency of the DSSCs. Here graphene oxide (GO) is added as an additive into the TiO2 network towards the preparation of TiO2/reduced graphene oxide (RGO) composites by UV assisted photocatalytic reduction method. The RGO/TiO2 composites with different compositions of RGO were characterized and the performance of DSSCs using the prepared material as photoanode was studied. Furthermore, through the D and G band Raman peaks, the reduction of GO to RGO was confirmed. The optical properties of the prepared material were analyzed using UV-visible spectroscopy and photoluminescence analysis, respectively. The carrier lifetime of the TiO2 and TiO2/RGO composites was studied using time resolved photoluminescence studies. The high-resolution transmission electron microscope images of prepared TiO2/RGO composites were found to have sheet-like structure surrounding the near spherical nanoparticles, which could be attributed to that of RGO and TiO2, respectively. The binding energy states of the prepared material were studied using X-ray photoelectron spectroscopy (XPS) spectra. The incorporation of RGO in TiO2 was found to improve the Brunauer–Emmett–Teller (BET) surface area of TiO2 and distribution of pores in TiO2 and TiO2/RGO composites was found to be uniform. The DSSCs were fabricated using the prepared TiO2 and TiO2/RGO composites as photoanodes and their power conversion efficiencies were analyzed.

Uniform dispersion of CuO nanoparticles on mesoporous TiO2 networks promotes visible light photocatalysis

Here, we focus our efforts on synthesizing a uniform dispersion of CuO nanoparticles on mesoporous TiO2 networks for the first time. H2PtCl6 was added through a photocatalytic reaction to produce 0.5% Pt/CuO–TiO2 nanocomposites. XRD patterns confirmed that the prepared TiO2 formed the anatase phase. TEM images showed close contacts between CuO and TiO2 with 5–10 nm particle sizes. One of the advantages of the synthesized mesoporous CuO–TiO2 nanocomposites was the high pore volume (0.540 cm3 g−1) and large surface area (300 m2 g−1). The H2 evolution over the mesoporous 3 wt% CuO–TiO2 nanocomposites using a glucose hole scavenger [10 vol%] was determined to be ~13000 μmol/g, a value that was 1300 times greater than that of mesoporous TiO2. The H2 evolution rate was increased by up to 1300 and 20 times for 3 wt% CuO–TiO2 and 0.1 wt% CuO–TiO2 nanocomposites, respectively, compared with that of mesoporous TiO2. The increase in H2 evolution over mesoporous CuO–TiO2 nanocomposites was explained by the increased light harvesting capacity, high glucose molecule diffusion and efficient charge carrier separation. Moreover, the construction of a heterostructure with a p–n CuO–TiO2 heterojunction expedited the separation of charge carriers and promoted the evolution of H2. In addition, H2 evolution was substantially increased by the synergistic effects of Pt and CuO on the mesoporous TiO2 networks. Photoelectrochemical and photoluminescence measurements were employed to prove the H2 evolution mechanism over the CuO nanoparticles deposited on the mesoporous TiO2 networks.

Non-isothermal crystallization of TeO2-Na2O-TiO2 glasses

Glass samples in the form 80TeO2-(20-x)Na2O-xTiO2 with x = 0, 5, 10, 15 and 20 mol%, were fabricated by the melting quenching technique. The thermal behavior of samples was analyzed considering their crystallization kinetics mechanism and microstructural analysis. Differential Scanning Calorimetry (DSC) was performed at 20 ml/min argon flux and heating rates of 10, 13, 15 and 20 K/min, from ambient temperature to 873 K, and these data were analyzed using a non-isothermal model of phase transformation. The activation energy for crystallization and Avrami exponent were determined for each sample. We observed that the crystallization process depends on the role assumed by the TiO2, a modifier (5 mol%) or former network (10 and 15 mol%). The crystallization process changes from superficial to internal or three-dimensional crystallizations with increasing TiO2 content.