CuO TiO2 Research Articles

Optical, structural and photocatalysis properties of Cu-doped TiO2 thin films

Pure and Cu+2 doped TiO2 thin films have been successfully deposited onto glass substrate by sol–gel dip-coating. The films were annealed at 450°C for 1h and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM-EDX), atomic force microscopy (AFM), UV–vis spectrophotometer and photocatalytic degradation of methylene blue. XRD confirmed the presence of two phases at higher Cu concentration; TiO2 anatase and CuO. AFM analysis showed that the surface roughness increases within increasing Cu content as well as the presence of large aggregates at higher Cu content. SEM observations confirmed the granular structure of the films, and EDX analysis revealed a low solubility limit (effective doping) of Cu into TiO2 lattice. It was found that the optical band gap energy decreases with increasing Cu content. At constant irradiation time, the photo-degradation of methylene blue rate decreased with increasing concentration of Cu+2.

Electrodeposition of flake-like Cu2O on vertically aligned two-dimensional TiO2 nanosheet array films for enhanced photoelectrochemical properties

A novel Cu2O/TNS composite structure of single crystal TiO2 nanosheet (TNS) arrays decorated with flake-like Cu2O were synthesized by a facile hydrothermal reaction followed by the electrodeposition process. The effects of deposition potential on the microstructure, morphology, and optical property of the thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectrophotometer. When the deposition potential is higher than −0.4V, peaks corresponding to Cu appear, meanwhile, flake-like Cu2O become agglomerating, and transform into dense Cu2O particles. Additionally, photoelectrochemical experiments indicate that the films deposited at −0.4V show the lowest resistivity and highest exciton separation efficiency. This enhanced photoelectrochemical properties can be explained by synergistic effect of p-type flake-like Cu2O and n-type TiO2 heterojunctions combined with two-dimensional TiO2 nanosheet with exposed highly reactive {001} facets.

Supported Photocatalyst Based on CuO–TiO2/Palygorskite Nanocomposite Material for Wastewater Treatment

This study deals with the immobilization of mixtures of two semiconductor oxides CuO and TiO2 on fibrous palygorskite clay mineral in order to evaluate their photocatalytic activity for removing Orange G dye as model pollutant from aqueous solutions. The elaboration of CuO–TiO2/Palygorskite nanocomposites was carried out by impregnation with Cu2+ of before hand synthesized TiO2 supported palygorskite (Pal) followed by air annealing for 5 h at 550 °C. In the composite materials, different CuO to CuO + TiO2 molar ratios were used in order to obtain a CuO content in the range 13–30 mol.%. XRD, SEM and TEM equipped with elemental EDS analysis are concordant for showing the crystallization of anatase TiO2 along with CuO whose average size of nanoparticles (NPs) are in the range 6 to 20 nm as determined by TEM. By increasing the CuO content the average size of this oxide remains constant at about 10 nm while that of TiO2 NPs is slightly decreasing from 8.4 to 5.1 nm. Both oxide NPs were successfully attached on palygorskite fibers where they form CuO–TiO2 heterojunctions (grain boundaries like). The CuO–TiO2/Pal supported photocatalyst containing 23% of CuO was found to be the most photoactive material but itremained less active than TiO2/Palygorskite supported photocatalyst. The photocatalytic activity of the mixed nanocomposites is not readily correlated with only one of their main features as CuO content or the average crystallite size of functional oxides indicating that if there are synergistic effects there are also antagonistic effects in particular for high CuO contents.

Microwave-assisted synthesis of CuO/TiO2 nanocomposite for humidity sensor application

Nowadays the sensors importance has been increased because of its various applications in almost all the existing fields. Present paper deals with CuO/TiO2 nanocomposites preparation, characterization and humidity sensor application. For this purpose, we report microwave-assisted synthesis of CuO/TiO2 nanocomposites using copper acetate, titanium tetra isopropoxide, sodium hydroxide and 1-ethyl-3-methyl-imidazolium-ethylsulfate (EMISE) as precursors. Structural properties of CuO/TiO2 was measured by X-ray diffractometer and it was found that the obtained nanocomposite contains monoclinic CuO and tetragonal anatase TiO2. Surface morphology of samples was observed by scanning electron microscope and transmission electron microscope. Cu–O and Ti–O–Ti bands were observed in Fourier transform infrared spectroscopy. The weight loss was investigated by thermo gravimetric analysis. The CuO/TiO2 pellets considered as sensing element, recorded resistance with respect to relative humidity. The sensitivity of sensing elements increased with annealed temperature.

Optimization of semiconductor ns-TiO2-CuO admixed photoelectrode for photoelectrochemical solar cell in regard to hydrogen production

This paper deals with the investigation on the optimization of ns TiO2–CuO admixed/Ti with respect to optimum photoelectrode area for semiconductor septum photo electrochemical solar cell. The motivation of the present work was to prepare an electrode having high effective surface area and hence better quantum yield and improved PEC activity. The photoelectrochemical response of ns TiO2-CuO photo electrodes for four different electrode area has been measured to explore the effect of electrode area on the output power in a chemical fuel (i.e. H2) produced by SC SEP PEC cell. This was done for determining the electrode area for optimum electrical output and hydrogen production. The photo electrochemical cell having ns TiO2-CuO admixed/Ti photoanode of several geometric areas like 0.5, 1.0, 1.5, 2.0 and 2.5 cm2 were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to 1.5 cm2.

Hybrid paper–TiO2 coupled with a Cu2O heterojunction: an efficient photocatalyst under sun-light irradiation

Hybrid paper–TiO2, paper–Cu2O–TiO2 and paper–TiO2–Cu2O photocatalysts were prepared via a non-hydrolytic sol–gel process followed by mild hydrothermal treatment to generate the TiO2 layer, and a reduction process to form the Cu2O nanoparticles.

Numerical and experimental investigation of flow structure and behavior of nanofluids flow impingement on horizontal flat plate

Numerical and experimental studies have been conducted to investigate flow structure and heat transfer of nanofluid jet normally impinging on a flat plate. Al2O3–water is used as working fluid. The governing equations are numerically solved using finite volume approach together with SIMPLER algorithm. A wide spectrum of experimental and numerical simulations has been done. The results covered wide ranges of Reynolds number, Re, from 3000 to 32,000, nanofluid volume fraction, ϕ, from 0 to 10%. The dimensionless distance from jet nozzle to the horizontal plate was kept constant at 3. An experimental apparatus was constructed to measure the film thickness distribution, wall temperature and temperature of flowing fluid. The effects of Re and ϕ are investigated on the film thickness distribution, isothermal contours, and both local and average Nusselt numbers. A good agreement was found between the numerical and experimental results as well as the previous cited results. The results showed that the increasing of nanoparticle percent increases the convective heat transfer coefficient compared with the pure water. At ϕ=10.0% and Re=24,000 the heat transfer coefficient increases by 62% compared with the pure water. The effect of nanofluid type (Al2O3–TiO2–CuO) is studied numerically. It has been observed that the CuO nanofluid increases the heat transfer by 8.9% and 12% compared to aluminum and titanium nanofluid respectively.

The role of CuO–TiO2 additives in the preparation of high-strength porous alumina scaffolds using directional freeze casting

Lamellar porous Al2O3 scaffolds with initial solid loading of 30 vol% were prepared by freeze casting using micron-sized Al2O3 powders as raw material and CuO–TiO2 additives as sintering aid. The effects of the composition of CuO–TiO2 on the microstructure, porosity and compressive property of the Al2O3 scaffolds were investigated and the mechanisms for sintering promotion addressed. The sintering aid effect was prominent when CuO:TiO2 was 1:2 in mass and their amount reached 3 wt% of the total ceramic powders. The corresponding compressive strength reached 176 ± 20 MPa with the porosity being 45 ± 1 % after sintering at 1450 °C for 2 h. Activation of the Al2O3 lattice due to partial substitution of Ti4+ for Al3+ and formation of a low-melting eutectic liquid were presumed to play a significant role in the sintering and strengthening of the Al2O3 scaffolds.

Photocatalytic degradation of gallic acid over CuO–TiO2 composites under UV/Vis LEDs irradiation

Coupling TiO2 with narrow band gap semiconductors has been a strategy to obtain visible light active photocatalysts. In this work we present, the characterization and photocatalytic results of high-loaded CuO–TiO2 composites prepared by impregnation of TiO2 powder (Evonik, P25) with copper acetate followed by calcination. The resulting composite materials were characterized by X-ray diffraction, nitrogen adsorption/desorption, UV–vis diffuse reflectance, scanning electron microscopy, X-ray photoelectron spectroscopy and time-resolved microwave conductivity. The photocatalysts were used to degrade gallic acid by using low power ultraviolet and visible light emitting diodes (UV-LED and Vis-LED) as light sources. According to the results, the photocatalytic degradation of the pollutant was efficiently converted to several intermediate products and partially mineralized to CO2 by using visible light. These results were explained in terms of an enhancement of the optical and electronic properties of TiO2 by the presence of Cu2O and CuO phases.

Adsorption and photocatalytic degradation of tetracycline hydrochloride using a palygorskite-supported Cu2O–TiO2 composite

A palygorskite (Pal)-supported Cu2O–TiO2 heterojunction composite (Cu2O–TiO2–Pal) was successfully prepared. The morphology, structure and chemical composition of the composite was characterized, and the adsorption and photocatalytic degradation of tetracycline hydrochloride using this composite was also investigated. The results showed that a layer of TiO2−Cu2O was successfully loaded on the surface of Pal. The Cu2O–TiO2–Pal composite had a specific surface area of 93 m2·g−1, mesoporous features, and a uniform slit channel. The composite possessed twofold removal ability to TC, including adsorptive capability for the separation and solar-light illuminate photocatalytic in degradation. The maximum adsorption capacity of Cu2O–TiO2–Pal for TC was 113.6mg·g−1 at 20°C as calculated by the Langmuir model. The pseudo-first-order degradation rate constant of 50mL of TC with an initial concentration of 30mg·L−1 reached 0.0129min−1 when the Cu2O–TiO2–Pal concentration was 1.0g·L−1. The total removal rate of TC reached 88.81% in the presence of Cu2O–TiO2–Pal. In addition, the composite could be regenerated by calcination at 400°C and recycled more than three times, which is useful for practical applications.

Microwave-assisted synthesis of rod-like CuO/TiO2 for high-efficiency photocatalytic hydrogen evolution

CuO-deposited TiO2 rod composites were prepared through a microwave-assisted green method for high efficiency hydrogen evolution. The porous CuO/TiO2 rods with crystallinity and high specific surface (249.1 m2/g) area were obtained as-synthesized without calcination. Hydrogen yields were proved to be significantly improved with appropriate amount of CuO deposited onto TiO2 rods. The improved photocatalytic performance was attributed to the synergistic effects of high surface area, specific energy band structure, and enhanced light harvesting at the interface of CuO and porous TiO2 rods.

Synthesis of Cu2O/graphene/rutile TiO2 nanorod ternary composites with enhanced photocatalytic activity

A ternary composite of Cu2O, graphene and rutile TiO2 nanorods was prepared using Cu(CH3COO)2·H2O, graphene oxide and TiCl4 as the starting materials and its enhanced photocatalytic performance was demonstrated. Graphene/TiO2 nanorod composites (GT) were obtained by a simple hydrothermal method and then, Cu2O was coupled onto the surface of graphene/rutile TiO2 to form Cu2O/graphene/rutile TiO2 nanorod (CGT) composites via a chemical bath deposition process. The as-prepared sample was characterized by X-ray diffraction (XRD), emission field scanning electron microscope (FE-SEM), transmission electron microscopy (TEM), specific surface area analyzer (BET), Raman spectroscopy and ultraviolet–visible diffuse reflectance spectroscopy (UV–vis DRS). It is found that the introduction of graphene and Cu2O has little effect on the morphology of TiO2 nanorods with average dimensions of 140 nm (length) × 30 nm (diameter) (L/D ratio ≈5). A red shift of light absorption edge and more absorption in the visible light region were observed for the resulted ternary samples compared with TiO2 and graphene/TiO2 composites. The photocatalytic activity was evaluated by the photodegradation of methylene blue under visible light irradiation, which showed 2.8 times corresponding enhancement of the degradation efficiency for the ternary composites compared with TiO2. This work provides a new strategy to improve the visible light response of TiO2 and facilitate its application in environmental remediation.

Improved photocatalytic activity of nano CuO-incorporated TiO2 granules prepared by spray drying

4wt% CuO–96wt% TiO2 granules were prepared by a spray drying process. The microstructure and optical property of CuO–TiO2 granules were studied. The results indicate that copper existed in the form of CuO. The spray dried granules possess spherical geometry and smooth surface with grain size in the range of 40–80μm. CuO–TiO2 has a relatively smaller Eg value (2.85eV) than TiO2 (3.17eV). The photocatalytic property of CuO–TiO2 granules was investigated by degradation of a model pollutant (the azo dye methyl orange) under the irradiation of the xenon lamp equipped with a band pass filter of 365nm. The CuO–TiO2 spray-dried granules degrade about 10% more MO than TiO2 spray-dried granules under UV irradiation within the same time. The XPS spectra suggested that Cu2+ and reduced copper species were coexistent in reacted CuO–TiO2 photocatalyst. The improvement of photocatalytic activity for CuO–TiO2 was mainly attributed to effective separation of photo-generated electron–hole pairs in the presence of CuO.

Magnetic Composite Fe<sub>3</sub>O<sub>4</sub>/CuO/TiO<sub>2</sub> Nanoparticles: Preparation, Characterization and Photocatalytic Activity

Magnetic composite Fe3O4/TiO2/CuO nanoparticles have been synthesized by sol-gel method at low temperature. The resultant composite nanoparticles coupled with different Cu contained by adjusting the molar ratio of CuO to (Fe3O4/TiO2) from 1:1 – 5:1. The structure, morphology and properties of nanoparticles were characterized using XRD, EDX, FESEM and VSM. The results showed that all composite nanoparticles consist of cubic spinel Fe3O4, anatase TiO2 and monoclinic CuO, have ferromagnetic properties. The photocatalytic performance was evaluated using methylene blue in aqueous solutions under UV and visible light irradiation. Among the composite Fe3O4/TiO2/CuO nanoparticles, the sample with the molar ratio of CuO to (Fe3O4/TiO2) = 5 : 1 exhibited the highest photocatalytic efficiency. Photocatalytic mechanism was investigated by measuring the photocatalytic degradation rate in the presence of scavenger. The results suggested that holes play the most important role in degradation of methylene blue.

Cu2O/TiO2 heterostructured hollow sphere with enhanced visible light photocatalytic activity

The Cu2O/TiO2 heterostructured hollow spheres (Cu2O/TiO2HS) were successfully prepared. The developed Cu2O/TiO2 heterojunction material has a spherical hollow structure with diameters about 750–950nm and shell thickness of 20–30nm, on which the p-type Cu2O and n-type TiO2 nanoparticles are closely contacted with each other. The well designed heterojunction structure is beneficial for the charge separation in photocatalytic reaction. The UV–vis absorption spectra showed that the Cu2O/TiO2HS catalyst displayed a better ability for visible light absorption compared to the pure TiO2HS. The as prepared samples showed improved solar light and visible light induced photocatalytic activities by decomposing Rhodamine B. The greatly enhanced activity can be attributed to the well designed heterojunction and the hollow structure of TiO2HS, which can simultaneously enhance the charge separation efficiency and facilitate the Rhodamine B adsorption.

CO2 photoreduction with water: Catalyst and process investigation

Economic development should not be separated from the concept of sustainability. The goal can be pursued by means of technologically advanced materials and processes that enable environmental protection. Carbon dioxide photoreduction using water as reducing agent could be a green and effective way to pursue this aim and titania is a good photocatalyst for this reaction. In this work the performances of N doped CuO–TiO2 photocatalysts in gas phase CO2 reduction have been studied. We have focused the attention on both the catalysts design and the process optimization. We have investigated, in particular, the effect of the presence of nitrogen and copper amount on the final catalysts performances. In order to learn high control of the catalytic process and to manage productivity and selectivity, by operating in very mild reaction conditions, the last part of the work has been centered on tuning the process parameters (CO2/H2O ratio). It has been observed that the CH4 formation is sensitive to copper amount and that exists a close correlation between the catalytic behavior and the reagents ratio.

Modified diatomite-supported CuO–TiO2 composite: Preparation, characterization and catalytic CO oxidation

Modified diatomite (acid treated and ZrO2-coated diatomite) coated by nano copper and titanium mixed oxides was used to investigate the catalytic oxidation of carbon monoxide. The prepared catalysts were characterized by Brunauer–Emmett–Teller (BET) surface area, field emission scanning electron microscope (FESEM), X-ray diffraction (XRD), temperature-programmed reduction (TPR), porosimetry, and X-ray photoelectron spectroscopy (XPS). Catalytic behavior for CO oxidation was studied in different conditions in a tubular reactor packed with catalyst. The variation of catalytic activity of the prepared composite catalysts with different molar fractions of CuO and TiO2 for CO oxidation in different reaction temperatures was investigated. The catalytic activity of catalyst was dependent on the concentration of coated catalyst over diatomite, reaction temperature and retention time. The results illustrated that diatomite is the promising candidate for catalyst support due to its unique characteristics. It was found that CO conversion of 100% can be achieved at 220 °C over catalyst with 70 mol% CuO and 30 mol% TiO2 content.

Multiplexed gas sensor based on heterogeneous metal oxide nanomaterial array enabled by localized liquid-phase reaction.

A novel method for the selective and localized synthesis of nanomaterials and their in situ integration based on serial combination of localized liquid-phase reaction has been developed for the fabrication of heterogeneous nanomaterial array. This method provides simple, fast and cost-effective fabrication process by using well-controlled thermal energy and therefore solves the challenging problems of assembly and integration of heterogeneous nanomaterial array in functional microelectronic devices. We have fabricated a parallel array of TiO2 nanotubes, CuO nanospikes, and ZnO nanowires, which exhibited adequate gas sensing response. Furthermore, we could approximately determine individual gas concentrations in a mixture gas consisting of 0-2 ppm of NO2 and 0-800 ppm of CO gas species by analyzing multiple data from an array of heterogeneous sensing nanomaterials.

Distinctive effects of TiO2 and CuO nanoparticles on soil microbes and their community structures in flooded paddy soil

The wide use of metal oxide nanoparticles (MNPs) will inevitably increase their environmental release into soil, which consequently raises concerns about their environmental impacts and ecological risks. In this study, two typical MNPs (TiO2 and CuO NPs) in different doses (0, 100, 500 and 1000 mg kg−1 soil) were applied to evaluate their effects on microbes in flooded paddy soil. The negative effects of CuO NPs were stronger than that of TiO2 NPs on soil microbes, as reflected by the significant decline in soil microbial biomass (as indicated by the reduced microbial biomass carbon [MBC] and the total phospholipid fatty acids [PLFAs]) and enzyme activities including urease, phosphatase and dehydrogenase. The principle component analysis (PCA) of the PLFAs and the diversity indices reveal that not TiO2 NPs but CuO NPs reduced the composition and diversity of the paddy soil microbial community. The reduced impact of TiO2 NPs may be due to their particle characteristics. The bioavailability of CuO NPs is thought to induce the major toxicity to microbes in the flooded paddy soil, as determined by the increased Cu contents in the soil extractions and the microbial cells. The elevated stress ratio values demonstrate that CuO NPs may also indirectly affect soil microbes by changing nutrient bioavailability. Over all, both TiO2 NPs and CuO NPs may induce perturbations on the microbes in flooded paddy soil and showed potential risks to the paddy soil ecosystem. Therefore, attentions toward the effects of MNPs to the ecological environment should be paid from now on.

Diffused sunlight driven highly synergistic pathway for complete mineralization of organic contaminants using reduced graphene oxide supported photocatalyst

Diffused sunlight is found to be an effective light source for the efficient degradation and mineralization of organic pollutant (methyl orange as a probe) by sono-photocatalytic degradation using reduced graphene oxide (rGO) supported CuO–TiO2 photocatalyst. The prepared catalysts are characterized by XRD, XPS, UV–vis DRS, PL, photoelectrochemical, SEM-EDS and TEM. A 10 fold synergy is achieved for the first time by combining sonochemical and photocatalytic degradation under diffused sunlight. rGO loading augments the activity of bare CuO–TiO2 more than two fold. The ability of rGO in storing, transferring, and shuttling electrons at the heterojunction between TiO2 and CuO facilitates the separation of photogenerated electron–hole pairs, as evidenced by the photoluminescence results. The complete mineralization of MO and the by-products within a short span of time is confirmed by TOC analysis. Further, hydroxyl radical mediated degradation under diffused sunlight is confirmed by LC–MS. This system shows similar activity for the degradation of methylene blue and 4-chlorophenol indicating the versatility of the catalyst for the degradation of various pollutants. This investigation is likely to open new possibilities for the development of highly efficient diffused sunlight driven TiO2 based photocatalysts for the complete mineralization of organic contaminants.