Synergetic Effect Of Cu Research Articles

Cu/Cu+ Synergetic Effect in Cu2O/Cu/CF Electrocatalysts for Efficient Nitrate Reduction to Ammonia

Electrocatalytic nitrate reduction reaction (NO3–RR) has been considered a promising technology to produce ammonia but is inhibited by poor electrocatalytic performances. Therefore, the development of efficient electrocatalysts and investigation of corresponding reaction mechanisms are critically important. Herein, an efficient dendritic Cu2O/Cu grown on Cu foam (D-Cu2O/Cu/CF) has been synthesized by a facile electrodeposition method, and the synergetic effect of Cu and Cu+ in NO3–RR has been investigated. In situ and ex situ data testify the synergetic effect clearly that Cu sites are responsible for the beginning of nitrate conversion to nitrite, while Cu+ sites are the active center for subsequent nitrite reduction to ammonia. In addition, in situ-generated active Cu+ sites further enhance the catalytic performances. Therefore, an extraordinarily high nitrate removal rate of 98.9% together with a relatively high ammonia yield rate of 11.2 mg h–1 cm–2 can be obtained in electrolytes containing 90 ppm of nitrate.

Ocean acidification increases copper accumulation and exacerbates copper toxicity in Amphioctopus fangsiao (Mollusca: Cephalopoda): A potential threat to seafood safety

Ocean acidification (OA) and trace metal pollutants coexist to exert combined effects on the functions and services of marine ecosystems. Increasing atmospheric carbon dioxide has caused a decrease in the pH of the ocean, affecting the bioavailability and speciation of trace metals and consequently altering metal toxicity in marine organisms. As an important trace metal functioned in hemocyanin, the richness of Copper (Cu) in octopuses is remarkable. Therefore, the biomagnification and bioaccumulation capacities of Cu in octopuses may be a non-negligible risk of contamination. Here, Amphioctopus fangsiao was continuously exposed to acidified seawater (pH 7.8) and copper (50 μg/L) to investigate the combined effect of ocean acidification and Cu exposure on marine mollusks. Our results showed that A. fangsiao could adapt well to ocean acidification after 21 days of the rearing experiment. However, the accumulation of Cu in A. fangsiao intestine increased significantly in acidified seawater under high levels of Cu stress. In addition, Cu exposure can influence the physiological function of A. fangsiao, including growth and feeding. This study also demonstrated that Cu exposure disturbed glucolipid metabolism and induced oxidative damage to intestine tissue, and ocean acidification further exacerbated these toxic effects. The obvious histological damage and microbiota alterations were also caused by Cu stress and its combined effect with ocean acidification. At the transcription level, we found numerous differentially expressed genes (DEGs) and significantly enriched KEGG pathways, involving glycolipid metabolism, transmembrane transport, glucolipid metabolism, oxidative stress, mitochondrial, protein and DNA damage, all revealing the strong toxicological synergetic effect of Cu and OA exposure and the molecular adaptation mechanism of A. fangsiao. Collectively, this study demonstrated that octopuses may withstand future ocean acidification conditions, however, the complex interactions of future OA and trace metal pollution need to be emphasized. OA can influence the toxicity of trace metals, inducing a potential threat to marine organism safety.

Interfacial ensemble effect of copper nanoparticles and nickel metal-organic framework on promoting hydrogen generation

Ammonia borane is a promising chemical hydrogen storage material to the hydrogen economy in the future. However, efficient and inexpensive catalyst for realizing this process remains challenging. Herein, the interfaces of copper nanoparticles (NPs) and nickel metal-organic framework (MOF) with different Cu/Ni ratios (Cu@Nix-MOF) have been constructed by Cu NPs in situ growth in Ni-MOF via a facile one-step solvothermal method. The Cu@Nix-MOF composites show much higher catalytic activity than their monometal counterparts and the optimized Cu@Ni6-MOF catalyst achieves a turnover frequency of 69.1 min−1 for ammonia borane hydrolysis, superior to most reported Ni-based catalysts. Density functional theory simulation and in situ Raman spectroscopy analysis propose that this remarkable enhanced activity of Ni-based catalysts is induced by a synergetic effect of Cu–Ni2+ dual active sites at their interfaces. This study shows that the strategy of dual active sites hold great promise to achieve efficient non-noble metal catalysts toward heterogeneous catalysis.

A new insight into rapid oxidation of alloy 925 contaminated by oxide powder

Rapid oxidation takes place both in the laboratory and in industrial conditions when alloy 925 is contaminated by oxide powder, and the oxidation rate is much higher than normal. Herein, the rapid oxidation behavior and mechanism of alloy 925 were investigated by a series of comparison tests at 1160 °C. It is found that the oxide powder produced during the oxidation process is mainly composed of NiCr2O4 spinel, accompanied by NiO and NiMoO4. The oxide powder plays a triggering role in the rapid oxidation of alloy 925, as NiO has a strong affinity with O. A composition adjustment experiment of alloy 925 shows that rapid oxidation is the synergetic effect of Mo and Cu in the alloy. Mo and Cu easily combine to form low melting point eutectics. The formation and volatilization of MoO3 oxide can destroy the completeness of the protective oxide layer. The MoO3 flux can dissolve protective Cr2O3 and prevent the repair of the oxide layer and also promote the formation of nonprotective and easy-spall NiCr2O4 spinel. The synergetic effect of Cu and Mo in accelerating oxidation should be considered in any nickel-based alloy with a high content of Cu and Mo.

Synergetic effect of Cu and Mn oxides supported on palygorskite for the catalytic oxidation of formaldehyde: Dispersion, microstructure, and catalytic performance

In this study, palygorskite (Pal), a natural nanorod-like clay mineral, is applied as the support of mixed Cu Mn oxides for formaldehyde (HCHO) oxidation, with focus on their dispersion, microstructure, and relative role during the catalytic oxidation. The composite material loaded with Cu Mn oxides retains the nanorod-like morphology of Pal, while the oxide particles in the size of 10–40 nm are well dispersed in the slit pores stacked by rods of Pal. Most of the Cu Mn oxides on Pal are with spinel structure, where Cu2+ ions occupy the tetrahedral sites and Mn3+ ions occupy the octahedral sites. The Pal-supported Cu Mn oxides achieves 90% CO2 generation at 207-258 °C, and displays better catalytic performance than solely supported catalyst. The presence of Cu obviously improves the reducibility of composite and the adsorption of HCHO, resulting in the acceleration of HCHO oxidation. The water resistance of composite catalyst also enhances with the increase of Cu content. Based on all these benefits, the catalytic performance of Cu Mn oxides on Pal can be optimized with an increase of Cu level.

Morphological evolution of Cu doped ZnO for enhancement of photocatalytic activity

Abstract The structure, morphology and chemical doping in metal oxide are important factors that can influence on its photocatalytic activity. In this work, a facile and template free reflux method has been used to synthesize ZnO nanostructures for the morphology control of cubes, maize corn seeds, and rods at low temperature. The photocatalytic activity of ZnO with different morphology was evaluated towards degradation of methyl orange under UV light illumination. Among all the morphology controlled ZnO, the maize corn seed shaped ZnO shows the superior photocatalytic activity. Moreover, the influence of Cu contents on the structural, optical, and photocatalytic activity of ZnO maize corn seed was also investigated systematically. The photocatalytic experiment towards the degradation of methyl orange revealed that the 0.5 mol% Cu doped ZnO exhibits 3.5 fold higher photocatalytic activity than pure corn seed shaped ZnO. The enhancement of photocatalytic activity by Cu ions substituting in ZnO lattices is attributed to synergetic effect of Cu and ZnO, increase the separation of photogenerated electron-hole pairs, oxygen vacancy, decrease in crystallite size and the higher surface to volume ratio. Based on scavengers test, it was found that both superoxide and hydroxyl radicals are mainly actives species involved for the degradation of methyl orange.

Synergetic effect of Cu and pentacoordinate Al3 + sites: Direct synthesis of ethyl ethoxyacetate via hydrogenation of diethyl oxalate

A novel Cu/Al2O3 catalyst is prepared and a distinguished product ethyl ethoxyacetate (EEA) is obtained from diethyl oxalate hydrogenation. Meantime, the traditional product like ethylene glycol is avoided. Furthermore, the EEA yield can be controlled by regulating the amount of pentahedrally coordinated Al3+ ions via varying either complex agent or calcinations temperature. As a result, the selectivity to EEA achieves a maximum of ca. 60wt% due to the synergism between the surface medium acidic sites derived from pentahedral coordinated Al3+ cations and active copper sites.

Synthesis and characterization of Cu–Zn/TiO2 for the photocatalytic conversion of CO2 to methane

ABSTRACTDifferent Cu–Zn/TiO2 catalysts were synthesized by using the wet impregnation method. The prepared catalysts were used for the conversion of CO2 into methane by photocatalysis. Various characterization techniques were used to observe the surface morphology, crystalline phase, Brunauer–Emmett–Teller (BET) surface area, presence of impregnated Cu and Zn, and functional group. Scanning electron microscope analysis showed spherical morphology, and slight agglomeration of catalyst particles was observed. BET analysis revealed that the surface area of the catalyst was decreased from 10 to 8.5 m2/g after impregnation of Cu and Zn over TiO2 support. Synergetic effect of Cu and Zn over TiO2 support (Cu2.6/TiO2, Zn0.5/TiO2 and Cu2.6–Zn0.5/TiO2) and the effects of Cu loading (0, 1.8, 2.1, 2.6 and 2.9 wt%) were also investigated at different feed molar ratios of H2/CO2 (2:1 and 4:1). The Cu2.6–Zn0.5/TiO2 catalyst showed a maximum conversion of 14.3% at a feed molar ratio of 4. The addition of Zn over the catalyst surface increased the conversion of CO2 from 10% to 14.3% which might be due to synergy of Cu and Zn over TiO2 support.

Synergetic effect of Cu–Pt bimetallic cocatalyst on SrTiO3 for efficient photocatalytic hydrogen production from water

The introduction of the Cu–Pt bimetal results in a significant improvement in the photocatalytic activity of STO. The hydrogen generation rate over STO/Cu95–Pt5 was about 46.6 and 2.79 times of STO and STO/Cu100–Pt0, respectively.

Synthesis of Cu@Pd core-shell nanowires with enhanced activity and stability for formic acid oxidation

A core-shell Cu@Pd nanowire with enhanced activity and stability for formic acid oxidation (FAO) was prepared by decorating Pd shell on the surface of Cu nanowire. Detailed characterization (XRD, TEM and HAADF-STEM) results confirm that the prepared nanowires are of Cu@Pd core-shell structure with enlarged surface areas. The catalytic activity of Cu@Pd/C (2197.88mA/mg at 0.257V) toward FAO is about 4 times higher than that of the commercial Pd/C (547mA/mg at 0.257V). The enhanced activity of the catalyst may mainly result from the synergetic effect of Cu and Pd, which was confirmed by density-functional theory (DFT) calculations.

Synergetic effect of Cu and graphene as cocatalyst on TiO2 for enhanced photocatalytic hydrogen evolution from solar water splitting

In photocatalytic solar water splitting systems, non-noble and highly active cocatalysts have always been pursued with tremendous interest. Herein an active and cheap photocatalyst, using Cu and graphene synergetically as co-catalysts immobilized on TiO2, was studied. This synergetic photocatalyst displayed enhanced photocatalytic hydrogen generation from water splitting in the presence of methanol as a sacrificial reagent. The hydrogen generation efficiency from the Cu–graphene synergetic cocatalyst was about 5 times higher than that of a pure graphene cocatalyst, and can be compared with that of systems containing the well-known Pt cocatalyst. Therefore this Cu–graphene synergetic cocatalyst provides an inexpensive means of harnessing solar energy to achieve efficient hydrogen evolution from water splitting.

Ru(III)‐catalyzed oxidation of cysteine hydrochloride by methylene blue in acidic medium; synergetic effect of Cu(II): A kinetic study

AbstractCysteine hydrochloride and methylene blue (MB) interact in a molar ratio of 2:1 in acidic medium forming cystine and dihydromethylene blue, and the reaction is catalyzed by Ru(III). At low concentrations (ca. 2.0 × 10−8 M), Cu(II) does not catalyze the reaction significantly but at this concentration level the catalytic activity of Ru(III) is found to be augmented by the addition of Cu(II) and the kinetics of Ru(III)‐catalyzed reaction has been studied in the absence and in the presence of externally added Cu(II). The reaction follows a half‐order kinetics in MB that increases to ¾ on increasing [MB] beyond 1.5 × 10−5 M in the Ru‐catalyzed reaction. In the Ru–Cu catalyzed reaction; the order in MB is ¾ even at lower concentrations of MB. The order in cysteine is unity. The rate decreases on increasing [MB] in both cases but attains a limiting value at higher concentrations of MB (ca. >2.0 × 10−5 M) in the presence of Ru(III) alone. The rate increases on increasing [H+] and in Ru‐catalyzed reaction, an optimum is noticed. The rate increases linearly with increasing [Ru(III)], but equilibration of the catalyst with other ingredients of the reaction system decreases the rate. The FTIR spectra of the reaction system exhibit time‐dependent changes in the stretching as well as bending modes of –SH group. The synergetic effect of Cu(II) has been attributed to its ligation with cysteine and its subsequent interaction with Ru(II) produced in situ in the system. © 2008 Wiley Periodicals, Inc. Int J Chem Kinet 40: 145–150, 2008

Development of a microchannel reactor concerning steam reforming of methanol

Abstract To develop a portable power device using fuel cell technology, the miniaturization of the hydrogen production unit is indispensable. In this paper, preparation of a microchannel reactor concerning steam reforming of methanol (SRM) has been investigated by optimizing the parameters of diffusion bonding and the composition of catalyst coatings. The results show the microchannel reactor can be sealed successfully by diffusion bonding at the optimized parameters (900 °C, 20 MPa, 1 h). The most active and selective catalyst coating is Cu50/Zn50 [Ce5] (Cu/Zn/Ce = 50/50/5, molar). It has been found that CeO 2 has an important influence on improving catalytic activity, decreasing the outlet CO concentration, and strengthening the stability. Based on the characterization of catalyst coatings, it can be attributed to the increase in copper area and to the change in oxidation state of copper that results in the synergetic effect of Cu 0 and Cu + . In addition, the effects of reaction temperature, space velocity, molar ratio of methanol to water, and reaction time were also investigated in the developed microchannel reactor with the Cu50/Zn50 [Ce5]. The results show that the microchannel reactor can generate enough hydrogen for a power output of 11 W.

Corrosion and biocompatibility testing of palladium alloy castings

Objectives: The biocompatibility of palladium–copper alloys has been questioned in the literature. The intention of the present work was to study: (a) the release of ions in an immersion test from a copper-containing alloy, Option ® (79% Pd, 10% Cu, 9% Ga, 2% Au), compared with an alloy without Cu, IS85 (82% Pd, 6% Ga, 3.5% Sn, 3.5% In, 2.5% Ag, 2.5% Au); (b) the effect of oxide films produced by preoxidation on corrosion resistance; and (c) the possibility of biologically synergetic effects of ions released. Methods: Specimens of both alloys were cast, rubbed and ultrasonically cleaned. Metallographic specimens were prepared after (a) casting and (b) preoxidizing treatment at approximately 1000°C and studied by SEM and EDS. Immersion tests were carried out in a solution of 0.1 mol/l of NaCl and 0.1 mol/l of lactic acid at 37°C for 7 days. The alloy specimens were tested in the following three steps: (1) as preoxidized; (2) after subsequent removal of a 0.1 mm thick layer by grinding; and (3) after an additional removal of approximately 0.1 mm by grinding. The test solutions were analyzed by means of ICP to record the amounts of ions that had leached out from the alloy specimens. The biocompatibility was studied by cell culture tests and the HET-CAM method. Test solutions were prepared by dissolving PdCl 2 and CuCl 2 to appropriate concentrations. Results: The metallographic investigations revealed moderate segregations in interdendritic regions and grain boundaries. After preoxidation in air a zone of oxidation from 25 up to 200 μm thickness for Option and from 5 to 10 μm for IS85 was found. Oxidation was observed along a rim for both alloys and for Option also along interdendritic positions. The oxides were seen as small, dark spots <1 μm in a metallic matrix. These results indicate that: (1) the oxidation of the copper-containing palladium alloy is far more severe than that of the alloy with no copper; and (2) the elemental release from these oxides is substantially larger than that from the corrosion of the metallic structure. The results of the cell culture testing showed that Cu was most toxic, followed by Cu 2++Pd 2+ (1:2), based on the determination of the concentration that caused 50% cytotoxicity. The HET-CAM testing showed Cu 2++Pd 2+ (1:2) to have the highest irritation score. Significance: The copper-containing Pd alloy developed a 0.1 mm thick rim with small oxide particles in a metallic matrix during preoxidation. If this rim is not completely removed, significantly more Cu, Ga and Pd ions have been shown to leach into the test solution than from the alloy structure. No synergetic effect of Cu and Pd ions was observed in cultured cells, while the mixture Pd 2++Cu 2+ (1:2) was most irritating to mucous membrane as evaluated by the HET-CAM method.