As-prepared CuO Research Articles

Facile dicyandiamide-mediated fabrication of well-defined CuO hollow microspheres and their catalytic application

Nearly monodisperse CuO hollow microspheres were successfully synthesized by a straightforward one-pot hydrothermal approach using dicyandiamide (DDA) as structure-guiding agent. The composition, structure and morphology of the products were investigated in detail, via a set of characterizations including X-ray diffraction (XRD) pattern, energy dispersive X-ray (EDX), scanning electron microscope (SEM), and transmission electron microscope (TEM). The results demonstrated that different copper sources and experimental procedures would significantly affect the shape or size of CuO products. A possible formation mechanism of CuO microspheres in this process was thoroughly discussed. Also, some other novel CuO microstructures were fabricated based on DDA-mediated synthetic route. DSC/TGA analysis revealed that as-prepared CuO microspheres can be explored as a promising additive to accelerate the thermal decomposition of ammonium perchlorate, a key oxidizer in composite solid propellants.

Effects of Chlorine Ion on the Photocatalytic Activity of Cuprous Oxide Powders Prepared by Hydrothermal Method

Cuprous oxide(Cu2O) microcrystals were successfully synthesized via hydrothermal method using CuSO4•5H2O and Na2SO3 in HAc-NaAc buffer solution. The products were characterized by X-rays diffraction (XRD) ,scan election microscopy (SEM) and ultraviolet-visible (UV-vis) spectroscopy. The photocatalytic activity of the as-prepared Cu2O powders was evaluated by the photocatalytic degradation of methyl orange solution under visible light irradiation at room temperature in air. The effects of chlorine ion on the photocatalytic activity of the Cu2O powders were investigated and discussed. The results show that chlorine ion in solution can obviously decrease the photocatalytic activity of Cu2O. When the concentration of chlorine ion increased to 0.5mol/L(about Cl- concentration in the seawater), the photocatalytic ratio of Cu2O decrease to 45% compared with the value in pure water. Increasing solution pH can enhance the photocatalytic activity of Cu2O. The mechanism of photo-degradation was discussed.

Synthesis and Gas Sensing Properties of Urchin-Like CuO Self-Assembled by Nanorods through a Poly(ethylene glycol)-Assisted Hydrothermal Process

Urchin-like CuO, consisting of closely packed nanorods with a diameter of 10nm, have been successfully synthesized by a poly(ethylene glycol) (PEG)-assisted hydrothermal route at low temperature of 100°C. The as-obtained Urchin-like CuO were thoroughly characterized by X-ray diffraction (XRD) study, Field emission scanning electron microscope (FESEM), High-resolution transmission electron microscopy (HRTEM) and Gas sensor measurements. From the XRD pattern, all the peaks detected can be assigned to CuO in a monoclinic structure with lattice parameters a=4.662, b=3.416 and c=5.118 (JCPDS card no. 65-2309). The FESEM and TEM showed that the diameter of the urchin-like CuO sphere is about 1µm. Further investigation of the formation mechanism reveals that the PEG-assisted hydrothermal process is vital to the formation of 3D structures. Besides the template function, PEG often plays as a reductant while reacting with Cu(+2). In our case, no impurity peaks of Cu2O were observed in the XRD pattern, implying that PEG did not reduce Cu(+2) to Cu(+1). We attribute this to the high concentration of PEG. The sensor based on the urchin-like CuO nanostructures exhibit excellent ethanol-sensing properties at reduced working temperature (200°C), which shows a sensitivity two times higher than that of CuO particles(about 100nm, made from calcinations of Cu(NO3)2 at 400°C). The enhancement in sensitivity of the as-prepared CuO may be contributed to the fancy 3D nanostructures.

CuO–CeO 2 binary oxide nanoplates: Synthesis, characterization, and catalytic performance for benzene oxidation

This work reports the first synthesis of CuO–CeO 2 binary oxides with a plate-like morphology by a solvothermal method. The as-prepared CuO–CeO 2 nanoplates calcined at 400 °C were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectrum, and tested for catalytic oxidation of dilute benzene in air. Various structural characterizations showed that large amounts of copper species were exposed on the CuO–CeO 2 nanoplate surface. The effect of the synthesis conditions on the structure of the product, as well as the growth process of the nanoplates, has been studied and discussed. The CuO–CeO 2 nanoplates exhibited an excellent catalytic activity for benzene oxidation despite its relatively low surface area and could catalyze the complete oxidation of benzene at a temperature as low as 240 °C.

Self-assembled CuO nanoarchitectures and their catalytic activity in the thermal decomposition of ammonium perchlorate

CuO shuttle-like and flower-like nanocrystals were synthesized through a one-step, low-temperature solution-phase method in the presence of a cation surfactant, hexadecyl trimethyl ammonium bromide. These nanocrystals were studied as an additive for promoting the thermal decomposition of ammonium perchlorate (AP). With the addition of CuO shuttle-like and flower-like nanocrystals, the thermal decomposition temperature of AP decreased. The structure, particle size, and morphology of resulting CuO powders were characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy. Thermogravimetric analysis technique was applied to investigate the thermal decomposition of mixtures of AP and as-prepared CuO nanocrystals.

From Cu2(OH)3Cl to nanostructured sisal-like Cu(OH)2 and CuO: Synthesis and characterization

Cu 2 ( OH ) 3 Cl with an average size of 5–10 μm have been synthesized by a simple hydrothermal reaction with a yield of ∼100%. After the as-prepared Cu2(OH)3Cl was treated with NaOH solution, the green crystals were converted to blue sisal-like Cu(OH)2 with needle-like nanorods pointing out radially from the core. These nanorods were about 100–200 nm in diameter and 10 μm in length. Using the sisal-like Cu(OH)2 as sacrificial precursor, CuO with a well-preserved morphological feature of the precursor was formed through thermal treatment. The samples were characterized by scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, X-ray photoelectron spectroscopy, BET nitrogen adsorption, and UV-visible absorption spectroscopy. The conversion of the synthesized Cu2(OH)3Cl to sisal-like Cu(OH)2 was optically visualized and confirmed by corresponding SEM images, and an “etching-and-growing” mechanism was proposed. The results also show that the as-prepared CuO possesses a band gap of 2.27 eV and high specific surface area (75.8 m2/g), and its surface is highly rich in O.

Rapid room-temperature fabrication of Cu2O–Au core–shell nanospheres

A facile, template-free method is reported to prepare Cu2O/Au core–shell nanospheres in aqueous medium at room temperature. In this synthesis, Cu2O nanospheres with definite diameter were first synthesized via the reduction reaction between Cu(NO3)2 and hydrazine (N2H4). Then, the as-prepared Cu2O nanospheres were employed as nucleation centers for deposition of Au shell, resulting in the formation of core–shell nanospheres. The samples obtained at various stages after the addition of the HAuCl4 were studied by TEM observation. These TEM images revealed that the formation hollow interior space between the core and the shell. In addition, UV–vis spectra results indicated that the optical property of the Cu2O/Au core–shell nanospheres was influenced by the size of the hollow interior spaces between the cores and the shells.

Electrochemical performance of polycrystalline CuO nanowires as anode material for Li ion batteries

CuO nanowires were prepared by wet-chemical method through the reaction of CuSO 4, KOH and ammonia in aqueous solution and subsequent aging process. The XRD, SEM, TEM, HRTEM, CV and galvanostatic method are used to characterize the structure, morphology and electrochemical performance of the as-prepared CuO nanowires. The CuO nanowires are polycrystalline microstructure, which facilitates the electrochemical storing Li. Therefore, the polycrystalline CuO nanowires exhibit a good electrochemical performance as Li ion batteries anode. The CuO nanowires showed a high reversible capacity of 720 mAh/g. The capacity keeps up 650 mAh/g over 100 cycles.

Ultrasound-assisted preparation, characterization and properties of porous Cu2O microcubes

Porous Cu2O microcubes have been successfully synthesized via an in situ ultrasound route at an ultrasound power of 90% for 3 h in the presence of polyvinylpyrrolidone (PVP), employing CuCl2·2H2O, C6H12O6·H2O, trisodium citrate and NaOH as starting reactants. The phase and morphology of the product were characterized by means of powder X-ray diffraction (XRD), energy dispersive spectrometry (EDS), transmission electron microscopy (TEM), and field emission scanning electron microscopy (SEM). The investigations showed that the as-prepared porous Cu2O microcubes possessed good electrochemical properties and could photocatalytically degrade organic dye pyronine B under irradiation with 254 nm UV light, and could obviously restrain the propagation of E. coli.

Synthesis and electrochemical properties of CuO nanobelts

CuO nanobelts have been successfully prepared with high yield via a simple hydrothermal reduction process at a low temperature. The as-prepared CuO nanowires were characterized by XRD, SEM, TEM and HRTEM techniques. The growth mechanism of these nanostructures is discussed. The electrochemical tests show that the ultrafine CuO nanobelts, as a promising electrode material, can deliver a large discharge capacity of about 500 mA h g −1 .

Preparation and formation mechanism of mesoporous CuO–CeO 2 mixed oxides with excellent catalytic performance for removal of VOCs

A simple route has been developed to synthesize mesoporous CuO–CeO 2 mixed oxides. X-ray diffraction, N 2 adsorption and desorption isotherms, and high-resolution transmission electron microscopy have been used to characterize the obtained mesoporous CuO–CeO 2 mixed oxides. The results revealed that the as-prepared CuO–CeO 2 mixed oxides possessed a high BET surface area and pores in the range of 1–10 nm after calcination at 600 °C for 4 h. In order to understand the formation mechanism of the mesoporous structure, the precursor before calcination was characterized by FTIR and TG-DSC. The results showed that the formation of the mesoporous structure with the high BET surface area was ascribed to the decomposition of ammonia nitrate. Further experimental investigations revealed that the amount of ammonia nitrate in the precursor greatly influenced the BET surface area and the pore size of the final product. Furthermore, the method could be extended to the synthesis of other mixed oxides with the mesoporous structures, such as ZrO 2–CeO 2 and ZrO 2–Y 2O 3. The as-prepared mesoporous CuO–CeO 2 sample with the high surface area exhibited highly reducible features as compared to the sample with a low surface area. The mesoporous CuO–CeO 2 powder showed excellent catalytic activity for the complete oxidation of benzene.

Structure and size effect of CuO nanowires prepared by low temperature solid-phase process

CuO nanowires with an average diameter of 10 nm, and lengths of up to 1000 nm were synthesized by a solid-phase approach in the presence of shape control agent, PEG 600. The as-prepared CuO nanowires were characterized by XRD, TEM, SAED and HRTEM techniques. The Raman optical property of the CuO nanowires was investigated by Raman spectroscopy, indicating that the Raman peaks are broadened and red-shifted 23 cm − 1 compared with that of bulk CuO crystals. A rational explanation for the red-shifted and broaden of Raman peaks was discussed in detail according to phonon confinement model of an infinite crystal.

A comparison of anodically grown CuO nanotube film and Cu2O film as anodes for lithium ion batteries

CuO nanotube film and Cu2O film were anodically grown on Cu substrates through direct oxidation and electrochemical anodic reduction, respectively. The microstructure and morphology of the films were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The obtained CuO is monoclinic crystallization, and the diameters of tubes are about 100–300 nm, while the as-prepared Cu2O has a typical structure with a space group Pn3m and consists of compact faceted crystals. As anodes for Li-ion batteries, the electrochemical properties of the nanostructured CuO and Cu2O films were investigated by cyclic voltammogram and galvanostatic charge–discharge tests. An “apparent charge capacity” was introduced to describe the electrochemical performance. The initial apparent discharge capacity of the CuO and Cu2O film electrode reached to 911 and 570 mAh/g, respectively. Although they exhibited large irreversible capacities attributed to the formation of solid electrolyte interface (SEI) during the first cycle, the CuO nanotube film and Cu2O film had good cyclability and delivered the apparent capacity of 417 and 219 mAh/g after 30 cycles, respectively.

CuO particles and plates: Synthesis and gas-sensor application

We reported on the synthesis and gas-sensor application of copper oxide particles and plates. CuO particles were prepared by a thermal decomposition method, while CuO plates were obtained by a hydrothermal route. The sensitivity of the as-prepared CuO to NO 2 gas and alcohol at varied temperatures was studied systematically. The results revealed that the as-synthesized products had high sensitivity and quick response/recovery time at an operating temperature of 200 °C. Furthermore, the CuO plates displayed higher sensitivity to NO 2 gas than that of the corresponding particles. This research indicated that CuO plates have potentials in the applications of sensors.

Flower-like CuO film-electrode for lithium ion batteries and the effect of surface morphology on electrochemical performance

Nanostructured CuO films with flower-like architectures were fabricated by immersing copper foils in an aqueous solution of sodium hydroxide and sodium dodecylsulfate, and subsequent heat treatment at low temperature. The as-prepared CuO films exhibited not only higher reversible capacity but also better rate capability than those of network-like counterpart as negative-electrodes of lithium ion batteries. The effect of surface morphology on the electrochemical performance of the CuO electrodes was discussed. It was confirmed that the unique flower-like structures are mainly responsible for the difference in electrochemical performance between the two kinds of electrodes. The result of this study provides an attractive electrode with high energy-density for lithium ion batteries via a simple and green procedure.

Fabrication of CuO film with network-like architectures through solution-immersion and their application in lithium ion batteries

A novel CuO negative electrode with network-like architectures was fabricated on copper substrate by a simple solution-immersion step and subsequent heat treatment, which avoids the use of binder and conducting agent that necessary to the conventional electrode-preparation process. The as-prepared CuO electrodes exhibit not only high reversible capacity but also long cycling life, high rate capability in Li ion batteries. The result of this approach creates a new and attractive negative electrode with good electrochemical performance, which is simple, mild conditions, low cost, and easy control. It also opens a pathway for the application of other nanostructured materials of transition metal oxides in lithium ion batteries.

Fabrication of superhydrophilic Cu 2O and CuO membranes

The present work demonstrates a simple method on the direct preparation of Cu 2O and CuO membranes with super-hydrophilic property via calcination or reduction of the parent film of Cu(OH) 2. By controlling the reaction conditions, Cu(OH) 2 membranes with different surface patterns composed of nano-belts, whiskers, or stick-bundles were first prepared. Cu 2O and CuO membranes were obtained from Cu(OH) 2 membranes by subsequent reduction and dehydration, respectively. The patterns of the parent film of Cu(OH) 2 were kept in the as-prepared Cu 2O and CuO membranes. Interestingly, the Cu(OH) 2 crystals with various morphologies on the as-prepared film were all transformed to close-packed Cu 2O nanoparticles after the reduction. Wettability investigation reveals that both Cu 2O and CuO membranes have super-hydrophilic properties.

Room temperature growth of CuO nanorod arrays on copper and their application as a cathode in dye-sensitized solar cells

Vertically aligned CuO nanorod arrays on copper electrodes with diameters of ∼5 nm and lengths of hundreds of nanometers were synthesized successfully using a simple wet chemical method at room temperature. The composition, morphology, and growth conditions of the nanorods were characterized. We also show that the as-prepared CuO nanorod arrays are promising hole-transport media of dye-sensitized hetero-junctions for solar energy conversion.

Synthesis and characterization of CuO nanoparticles from liquid ammonia

A new type of CuO nanoparticles were synthesized in liquid ammonia in the presence of sodium metal. First, Cu nanoparticles were obtained by reducing copper nitrate with the alkali metal in liquid ammonia, then, CuO nanoparticles were formed in the ambient conditions. The morphology and structure of as-prepared CuO nanoparticles were characterized by TEM and XRD, and the reason of aggregation of CuO nanoparticles was supposed.

Highly dispersed CuO nanoparticles prepared by a novel quick-precipitation method

Highly dispersed copper oxide (CuO) nanoparticles with an average size of 6 nm have been successfully prepared by a novel quick-precipitation method. The as-prepared CuO nanoparticles were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Visible absorption spectroscopy and BET nitrogen adsorption. The results show that the as-prepared CuO nanoparticles have high dispersion and narrow size distribution. The influence of reaction conditions on morphology of CuO nanocrystals was discussed. Spherical, ellipsoidal and needle-shaped CuO nanocrystals can be obtained simply by varying the reaction temperature and controlling the addition of NaOH.