Electrochemical bulk synthesis and characterisation of hexagonal-shaped CuO nanoparticles

A simple and efficient two-step hybrid electrochemical–thermal route was developed for the bulk synthesis of CuO nanoparticles using aqueous sodium nitrate electrolyte and Cu electrodes in an undivided cell under galvanostatic mode at room temperature. The influence of electrolyte concentration on the synthesis of CuO nanoparticles was studied at 1.0?A/dm² current density. Electrochemically generated precursor was calcined for an hour at different levels of temperature in the range 200–900°C. The calcined samples were characterised by XRD, TG-DTA, XPS, SEM/EDAX, TEM, FT-IR and UV–Vis spectral methods. The crystallite sizes were estimated and the thermal behaviour of as-prepared compound was examined. Rietveld refinement of X-ray data shows results matching the monoclinic structure with the space group of C2/c (no. 15). The TEM result revealed that the particle sizes were in the order of 30–50?nm diameter and 120–200?nm length. The blue shift was noticed in UV–Vis absorption spectra. All samples of CuO exhibited randomly oriented hexagonal morphology.     

Thermoelectric properties of Cu2Sex prepared by solution phase methods and spark plasma sintering

Cu-Se compounds have attracted more attentions as a low-cost, low toxicity thermoelectric materials. In this work, p-type Cu₂Se_x compound powders were prepared by solution syntheses, including the wet chemistry method and hydrothermal synthesis method. The reaction mechanisms were investigated, showing that the NaOH contents affected the phase structure of the final product. Polycrystalline Cu₂Se_x bulk materials were obtained by densifying the powders using spark plasma sintering (SPS) and obtained the maximum ZT value of 0.75 at 623 K, which is currently the highest reported value for the Cu-Se system at this temperature. We also found that the introduced oxides could suppress the long-range migration of Cu ions in Cu-Se system to avoid the decomposition of the materials.     

Thermodynamic and experimental aspects on chemical looping reforming of ethanol for hydrogen production using a Cu‐based oxygen carrier

An investigation on the chemical looping reforming of ethanol process using Gibbs free energy minimization method was performed. It is found that the temperature, oxygen/ethanol molar ratio (OER), and pressure have pronounced influences on the product yields in chemical looping reforming of ethanol process. The ethanol conversion and H₂ yield are 100% and 2.25 mol mol^?1 ethanol, respectively, at 700 °C, OER of 1 and 1 atm. The higher temperatures promote H₂ and CO production, but the higher pressures and OERs have negative effect on the H₂ and CO generation. Favorable operation conditions are 1 atm, 700 °C, and OER = 1. The experimental tests were carried out in a fixed bed using a Cu‐based oxygen carrier prepared by impregnation method. Working at 1 atm, the H₂ concentration increased with an increase in temperature; however, it remained approximately with an increase in gas hourly space velocity. The H₂/CO molar ratio was between 3 and 5 in the period of 0–30 min at 1 atm and 700 °C. Copyright © 2013 John Wiley & Sons, Ltd.     

Hybrid sonochemic urea-nitrate combustion preparation of CuO/ZnO/Al2O3 nanocatalyst used in fuel cell-grade hydrogen production from methanol: Effect of sonication and fuel/nitrate ratio

Fuel cell-grade hydrogen production has been studied via steam reforming of methanol (SRM) over a series of CuO/ZnO/Al₂O₃ nanocatalysts fabricated by the combustion method. The effect of sonication and urea/nitrate ratio on the characteristics and catalytic properties of the prepared catalysts has been investigated. The synthesized catalysts were characterized by x-ray diffraction (XRD), field emission scanning electron microscope (FESEM), Particle Size Distribution (PSD), energy dispersive x-ray (EDX), Brunauer-Emmett-Teller (BET) and FTIR analyses XRD patterns showed positive influence of urea/nitrate ratio on CuO and ZnO crystallite sizes. The ultrasonic mixing of primary gel compared with conventional mixing led to lower crystallite size. FESEM images showed that the sample mixed by sonication with a urea/nitrate ratio of 1 had more homogeneous morphology with narrow particle size distribution. EDX results proved the presence of all metals on the surface of the nanocatalysts and better consistence between the gel and surface composition of elements in samples prepared by sonication. Catalytic performance showed that sonication during the mixing of primary gel dramatically increased the methanol conversion. It was also proved that increasing the amount of urea led to lower catalytic activity. The ultrasound-treated nanocatalyst with urea/nitrate?=?1 was the best sample in terms of activity and selectivity. It was stable in the SRM for 1200?min without considerable change in methanol conversion and product selectivity.     

Preparation and ethanol sensing properties of flower-like cupric oxide hierarchical nanorods

Flower-like cupric oxide (CuO) hierarchical nanorods (petal size: 60–100 nm in diameter and 500–700 nm in length) were synthesized by wet chemical-assisted hydrothermal processing. The samples were characterized by field emission scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. The influence of hydrothermal temperature on the formation of CuO nanoflowers was investigated. Sensors based on CuO nanoflowers were fabricated by coating them on SiO₂/Si substrate attached with Pt interdigitated electrodes. Sensing characteristics of the samples were measured and evaluated as a function of operating temperature and ethanol vapor concentration. The results revealed that the p-type semiconductor CuO nanoflowers based sensors exhibit high sensitivity and selectivity toward ethanol vapor with the optimum working temperature at about 230 °C.     

铜基催化剂的制备及其催化苯胺N-甲基性能

N-甲基苯胺(NMA)广泛应用于化工生产中,以苯胺和甲醇为原料,采用气相法合成NMA,研究的重点在于提高CuO/ZnO/Al_2O_3催化剂的稳定性。通过分析CuO/ZnO/Al_2O_3催化剂的制备条件及助剂的作用,为合成优良催化性能的催化剂提供理论指导。     

Preparation and characterization of CuO nanowire arrays

d to characterize the nanowire morphologies. Raman spectra were performed to study the CuO nanowire arrays. After measuring, we found that the current-voltage curve of the CuO nanowires is nonlinear.     

Capacitor Applications of Nanocomposite Films for Poly(3,4-ethylenedioxythiophene-co-pyrrole)/Multi-Walled Carbon Nanotubes and Poly(3,4-ethylenedioxythiophene-co-pyrrole)/Copper Oxide

Polypyrrole/multi-walled carbon nanotube, poly(3,4-ethylenedioxythiophene)/multi-walled carbon nanotube and their nanocomposites P(EDOT-co-Py)/multi-walled carbon nanotube and P(EDOT-co-Py)/copper (II) oxide, (CuO) in the initial feed ratio of [EDOT]₀/[Py]₀ = 1/5 were electrosynthesized on glassy carbon electrode by cyclic voltammetric method. Their characterizations were performed by cyclic voltammetric, Fourier transform infrared-attenuated total reflectance, scanning electron microscopy, energy dispersion X-ray analysis, and electrochemical impedance spectroscopy. To the best of authors’ knowledge, the first report on polypyrrole/multi-walled carbon nanotube, PEDOT/multi-walled carbon nanotube, P(EDOT-co-Py)/multi-walled carbon nanotube and P(EDOT-co-Py)/CuO nanocomposite films were comparatively examined in 0.1 M NaClO₄/CH₃CN and in 0.1 M sodium dodecyl sulfate solutions. The highest specific capacitance for PEDOT/multi-walled carbon nanotube and polypyrrole/multi-walled carbon nanotube composite films were obtained as C_sp = 306 mF × cm^?2 for 3% multi-walled carbon nanotube and C_sp = 804 mF × cm^?2 for 1% multi-walled carbon nanotube, respectively. The highest specific capacitances were obtained as C_sp = 27.40 mF × cm^?2 and C_sp = 26.90 mF × cm^?2 for P(EDOT-co-Py)/multi-walled carbon nanotube includes the wt percent of 1% multi-walled carbon nanotube and P(EDOT-co-Py)/CuO includes the wt percent of 3% CuO, respectively. The C_sp of P(EDOT-co-Py)/CNT composite films were calculated as 9.43 and 11.49 mF × cm^?2 for 3 and 5% multi-walled carbon nanotube, respectively. In addition, The EIS results were simulated with the equivalent circuit model of R_s(C_dl1(R₁(QR₂)))(C_dl2R₃).     

Low temperature sintering and dielectric properties of (Ba0.85Ca0.15)(Ti0.9Zr0.1)O3−xCu2+ ceramics obtained by the sol-gel technique

Lead-free Cu²⁺-modified (Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ (BCZT−xCu²⁺) piezoelectric ceramics was synthesized by sol-gel method. The effects of Cu²⁺ additions on sintering characteristics, the phase structure, microstructure, electrical properties and complex impedance characteristic were investigated systematically. The XRD patterns exhibited a pure perovskite structure without impurity phase in all samples. SEM micrographs, temperature dependence of dielectric constant and polarization-electric field (P-E) hysteresis loops indicated that a small amount of Cu²⁺ addition affected the properties obviously. The results revealed that the addition of Cu²⁺ significantly improved the sinterability of BCZT ceramics which resulted in a reduction of sintering temperature from 1440 °C to 1230 °C. The TG-DSC was analyzed to verify the reaction process of BCZT−Cu²⁺ materials. (Ba_0.85Ca_0.15)(Ti_0.9Zr_0.1)O₃ ceramics with x=0.020 Cu²⁺ exhibited good electrical properties: ε_m=12,112, T_c=360 K, ε_r=2614, tan δ=0.026, K_p=0.47 and d₃₃=382 pC/N. The results indicated that Cu²⁺-modified BCZT ceramics could be a promising candidate for commercial purposes.     

修饰的CuO/Fe2O3水煤气变换催化剂的性能测试与表征

ZrO₂是一种高熔点金属氧化物,同时具有弱酸性和弱碱性以及氧化性与还原性,具有p型半导体性质,易产生氧空穴,是理想的催化材料。通过添加不同质量分数的ZrO₂(0~5%) 作为助剂,采用分步沉淀法制备系列CuO/Fe₂O₃-ZrO₂催化剂,通过XRD、N₂物理吸附-脱附、H₂-TPR和CO₂-TPD等表征技术,考察ZrO₂助剂对CuO/Fe₂O₃水煤气变换催化剂催化性能的影响。结果表明,适量ZrO₂（质量分数1%）的添加,削弱了CuFe₂O₄中铜铁物种之间的协同作用,增加了催化剂中可被还原的铜物种的数量,形成较多的弱碱性位点,有利于增加活性中心铜的数量,具有较好的水煤气变换反应活性和热稳定性。