Single Copper Research Articles

Stable Cu (I) single copper atoms supported on porous carbon nitride nanosheets for efficient photocatalytic degradation of antibiotics

Stable Cu (I) single copper atoms supported on porous carbon nitride nanosheets for efficient photocatalytic degradation of antibiotics

Optimizing the reaction pathway of methane photo-oxidation over single copper sites.

Direct photocatalytic conversion of methane to value-added C1 oxygenate with O2 is of great interest but presents a significant challenge in achieving highly selective product formation. Herein, a general strategy for the construction of copper single-atom catalysts with a well-defined coordination microenvironment is developed on the basis of metal-organic framework for selective photo-oxidation of CH4 to HCHO. We propose the directional activation of O2 on the mono-copper site breaks the original equilibrium and tilts the balance of radical formation almost completely toward •OOH. The synchronously generated •OOH and •CH3 radicals rapidly combine to form HCHO while inhibiting competing reactions, thus resulting in ultra-highly selective HCHO production (nearly 100%) with a time yield of 2.75 mmol gcat-1 h-1. This work highlights the potential of rationally designing reaction sites to manipulate reaction pathways and achieve selective CH4 photo-oxidation, and could guide the further design of high-performance single-atom catalysts to meet future demand.

Copper‐graphene coatings for improving thermal shielding of CFRPs through electrodeposition techniques

AbstractToday, carbon fiber reinforced plastics (CFRPs) are materials of interest several industrial sectors because of their mechanical properties and low weight. However, applications in high‐temperature areas are limited because of thermal degradation. Thus, thin coatings acting as thermal shielding and ensuring the upkeep of CFRP structural stiffness are of high interest. This work presents an innovative approach to produce copper/graphene bilayer coatings through electrodeposition and electrophoretic deposition; it consists of laser pre‐treatment of the composite surface to remove the matrix layer exposing the carbon fibers, enabling the subsequent deposition. Bi‐layer graphene/copper coatings exhibit an enhancement in copper electrodeposition efficiency of more than 59% resulting in a 97% stiffness improvement compared to the single layer copper electroplating. All the obtained coatings were able to act as a thermal shield of the CFRPs, reducing the maximum temperature of the composite by more than 60%. In particular, due to the synergistic effect of copper and graphene, the GNPs‐Cu coating achieved the highest maximum temperature reduction (81%). Cross‐sectional analysis indicates severe delamination in uncoated CFRPs, whereas double‐layer coatings maintain structural integrity and prevent delamination even under high‐energy exposure. In addition, the coated composites exhibit a higher electrical conductivity compared to the laser cleaned CFRP, with the GNPs‐Cu coating that obtained a 90% enhancement because of the outstanding electrical properties of copper and graphene.Highlights The laser cleaning pretreatment allows the electrodepositions on CFRPs. The GNP‐Cu scenario achieves the highest deposition efficiency. A 97% stiffness improvement was achieved by GNPs‐Cu scenario. GNPs‐Cu coatings exhibit the utmost reduction in resistivity (98%). The GNPs‐Cu coating achieves the highest thermal shielding performance (81%).

FeSiBCuNbZr amorphous composites decorated with SiO2 and TiO2(B) (bronze phase TiO2) for efficient electromagnetic wave absorption

The application of Fe-based amorphous microspheres in high-performance electromagnetic wave absorbing materials is significantly limited by a single loss mechanism. Utilizing interfacial engineering and magnetic-dielectric synergistic effect is a viable approach to enhance microwave absorption. In this work, FeSiBCuNbZr amorphous microspheres were synthesized using single copper roller melt-spinning method and ball mill method. The finding reveals that the incorporation of SiO2 and TiO2(B) (bronze phase TiO2) shells notably enhances polarization loss and conductive loss. FeSiBCuNbZr@SiO2@TiO2(B) amorphous composites exhibited a minimum reflection loss value of −64.89 dB at a thickness of 2.17 mm and an effective absorption bandwidth (EAB) of 8.08 GHz covering 9–18 GHz at a thickness of 1.9 mm. The exceptional wave absorption performance is ascribed to the combined effect of magnetic loss in the FeSiBCuNbZr amorphous core and dielectric loss from the double-shell structure, while maintaining favorable impedance matching. This work provides a new core–shell FeSiBCuNbZr amorphous composites for efficient electromagnetic wave absorption.

The future of Ni-Cu smelting in Botswana: the choice between flash-smelting and top-submerged lance furnaces

The BCL furnace is scheduled to restart operations after being placed on care and maintenance in 2016 due to depressed nickel prices. The decision to start operations after such a stoppage ought to be led by a techno-economic evaluation of process options to make operations more resilient. For BCL, the decision lies between using the existing flash-smelting furnace (FSF) or a top-submerged lance (TSL) furnace. Available studies show that the FSF combined with other converting technologies is cheaper to operate; however, such studies are based on flowsheet simulation results of single copper concentrates and therefore do not provide a full scope of practical capabilities based on smelter operator skills. Using a t-test on normalized prior operational data from three Cu FSF and two Cu TSL, it was found that the only statistical differences between the operating costs of the FSF and TSL technologies are in the coal use for heating the feed blow and number of rebuilds: the FSF consumes coal to heat the feed blow and the TSL requires 2.4 rebuilds during a course of a single FSF campaign. A summative operating cost comparison over the existing BCL FSF 11-year life shows that BCL can decrease operational costs by some BWP 55.5 million if the operation were to change to the newer TSL technology. The savings derive from reduced coal use, which is normally associated with heating the blow when using the FSF. Despite the TSL carrying added costs of 2.4 rebuilds during a life time of one FSF furnace campaign, the cost associated with the TSL rebuilds of approximately BWP 1.3 million is minimal compared with the overall operational expenditure decrease that BCL will incur on using the TSL technology. In terms of the technology, BCL can have higher Ni-Cu recoveries at lower operational costs by elimination of Ni-Cu losses and eliminating the slag-cleaning furnace by converting to a TSL furnace.

Influence of surface structure and tube material on the condensation heat transfer coefficient of n-butane on horizontal single tubes and in tube bundles

The present study examines the condensation heat transfer coefficient αcond of n-butane on the outside of different horizontal tubes and in corresponding tube bundles. Experiments were conducted with a smooth tube, finned tubes with various fin densities, fin heights and tube materials, and a high-performance condensation tube (HPT) at vapor temperatures of (40 and 78) °C and varying heat flux densities q̇. The influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at q̇ of (20 and 60) kW·m−2. Differences between the experimental results from this work and previous ones for propane on the same condensation tubes could be explained with the help of the thermophysical properties and, thus, the retention angle of the condensate in the channels between the fins and the condensate layer thickness. For single copper tubes, αcond increased with increasing fin densities from (19 to 48) fins per inch and was between 9 and 17 times larger than for the smooth tube. This enhancement factor even reached a value of about 24 for the HPT. These increases can be attributed in part to the increased surface area, but the strongest effect appears to be related to surface tension-driven drainage of the condensate. In addition to the experimental investigations, αcond of the finned condensation tubes was predicted using an analytical model for the condensation heat transfer on finned tubes. Here, excellent agreement with an average deviation from the experimental results of 6.6 % could be found. Studies of the inundation effect have shown that the expected decrease in αcond due to the additional condensate impinging on the tubes inside bundles and increasing the film thickness often holds, but is partially counteracted by other effects and depends on the tube geometry.

Substituent Modulated Electronic Properties of Cu(I) Active Site in Metal–Organic Halides for Boosting Hydrogen Evolution Reaction†

Comprehensive SummaryDevelopment of heterogeneous molecular photocatalysts for promising light‐driven hydrogen evolution reaction (HER) is highly demanding but still challenging. Here, we report the blue‐greenish emitting dinuclear metal–organic halides as photocatalyst by incorporating site‐specific single copper(I) atoms that exhibit an efficient carbon‐negative H2 production. Interestingly, the electronic properties, including the spin and charge density of central Cu(I) active site, can be triggered by substituent modulation in metal–organic halides, which greatly affect the exciton dissociation kinetics and thus the HER reactivity. The optimized spin density in these heterogeneous photocatalysts drastically boosts the hydrogen production rate from 1250 to 3130 μmol·g–1·h–1. Our molecular strategy provides a platform that rationally facilitates electronic modulation of copper(I) atoms, tunes the macroscopic optoelectronic properties of photocatalysts and boosts carbon‐negative HER activity, extending the boundaries of conventional molecular‐based photocatalysts.

Enhancing radiation-resistance and peroxidase-like activity of single-atom copper nanozyme via local coordination manipulation

The inactivation of natural enzymes by radiation poses a great challenge to their applications for radiotherapy. Single-atom nanozymes (SAzymes) with high structural stability under such extreme conditions become a promising candidate for replacing natural enzymes to shrink tumors. Here, we report a CuN3-centered SAzyme (CuN3-SAzyme) that exhibits higher peroxidase-like catalytic activity than a CuN4-centered counterpart, by locally regulating the coordination environment of single copper sites. Density functional theory calculations reveal that the CuN3 active moiety confers optimal H2O2 adsorption and dissociation properties, thus contributing to high enzymatic activity of CuN3-SAzyme. The introduction of X-ray can improve the kinetics of the decomposition of H2O2 by CuN3-SAzyme. Moreover, CuN3-SAzyme is very stable after a total radiation dose of 500 Gy, without significant changes in its geometrical structure or coordination environment, and simultaneously still retains comparable peroxidase-like activity relative to natural enzymes. Finally, this developed CuN3-SAzyme with remarkable radioresistance can be used as an external field-improved therapeutics for enhancing radio-enzymatic therapy in vitro and in vivo. Overall, this study provides a paradigm for developing SAzymes with improved enzymatic activity through local coordination manipulation and high radioresistance over natural enzymes, for example, as sensitizers for cancer therapy.

FTIR Spectroscopy and Microstructural Study of Fe Doped Calcium Copper Titanate (CCTO)

Objectives : The analysis of present material is to reveal the effect of Fe atom by replacing the Ti atom in CCTO for chemical properties. Methods: Pure and Fe doped CaCu3Ti4-xFexO12 (x=0.05, 0.10, and 0.15) CCTO ceramics were synthesized by solid-state reaction route and calcination was done at 930°C for 12 hrs with heating rate of 4°C/min. The phase structure of samples was confirmed by X-ray Diffraction (XRD) and found single phase calcium copper titanate. Morphology of all samples was investigated by scanning electron microscopy. Absorption band have been also recorded for all samples. Findings: The structure remains cubic by doping of Fe atom in place of Ti atom. The average size of all the samples were lies between 1-1.3µm. Novelty: The bond strength becomes stronger as the doping of Fe atom takes place. The large absorption band is found in the range 380-700 cm-1. The peak of large band is shifted towards lower wave number. These higher wavelengths can be used in water pollutants. The increased volume size of samples shows lower energy band gap. This lower energy band gap enhanced the electrical properties. Keywords: FE­SEM, XRD, FTIR, EDS, CCTO

On the Efficiency of Air-Cooled Metal Foam Heat Exchangers

This study analyses the heat transfer performance of metal foam heat exchangers through experimental measurements. Using counter-gravity infiltration casting, open-cell aluminium foam elements were manufactured to embed a copper tube for internal mass flow containment. Heat transfer experiments were conducted under natural and forced convection conditions, with the airflow controlled in a wind tunnel. A stream of warm water within the internal foam component served as the heat source, transferring thermal energy to the surrounding air flowing through the external foam component of the heat exchanger. The results showed a significantly enhanced heat transfer performance with aluminium foam compared to a single copper tube. Thermal resistance models were developed to elucidate the heat transfer mechanisms, highlighting the effectiveness of air-cooled metal foam heat exchangers. These findings underscore the potential of metal foam heat exchangers as cost-effective alternatives for various thermal management applications.

Two tropical oligochaetes as potential standard test species: a case study evaluating single and combined copper and manganese toxicity

ABSTRACT The lack of toxicity tests using indigenous species in risk assessments of tropical regions has often been discussed. Thus, this study evaluated two tropical oligochaete species (Allonais inaequalis and Dero furcatus) for potential use as test species. To this end, the toxic effects of copper and manganese, both isolated and mixed, were evaluated for both species via acute tests. The test protocol developed by the Organisation for Economic Co-operation and Development (OECD) for temperate sediment-dwelling benthic oligochaetes could be successfully applied for both test species. The 96-h LC50 values (mean ± standard deviation) for D. furcatus were 31 ± 3 µg L−1 and 18 ± 0.061 mg L−1 for copper and manganese, respectively. The corresponding values for A. inaequalis were 26 ± 1 µg L−1 and 28 ± 0.063 mg L−1, respectively. Compared to the toxicity values for temperate arthropods, D. furcatus and A. inaequalis had comparable or greater sensitivity to the evaluated metals. The mixture toxicity tests indicated a dose ratio-dependent deviation of the concentration addition (CA) model, with antagonism occurring especially if the effects in the mixture were provoked by copper. Overall, these findings indicated that these taxa are sensitive candidates for use in tropical ecotoxicity testing. Future studies can elucidate the mechanisms of chemical mixture toxicity.

Synergistic rare-earth yttrium single atoms and copper phosphide nanoparticles for high-selectivity ammonia electrosynthesis

Synergistic rare-earth yttrium single atoms and copper phosphide nanoparticles for high-selectivity ammonia electrosynthesis

Modelling on a Biomimetic [Cu-O-Cu]2+-mediated Methane-to-Methanol Conversion Unveils the Site for Methane Activation.

The Cu-O-Cu core exhibits methane-to-methanol conversion, mirroring the reactivity of the copper-containing enzyme pMMO. Herein, we computationally examined the reactivity of a biomimetic Cu-O-Cu core towards methane-to-methanol conversion. The oxygen atom of the Cu-O-Cu core abstracts hydrogen present in the C-H bond of methane. The spin density at the bridging oxygen helps to abstract hydrogen from the C-H bond. We modulated the spin density of the bridging oxygen by substituting only a single copper atom of the Cu-O-Cu core by metals (M) such as Fe, Co, and Ag. These substitutions result in bimetallic [Cu-O-M]2+ models. We observed that the energy barriers for the C-H activation step and the subsequent rebound step vary with the metal M. [Cu-O-Ag]2+ exhibits the highest reactivity for M2M conversion, while [Cu-O-Fe]2+ displays the lowest reactivity. To understand the different reactivity of these models towards M2M conversion, we employed distortion-interaction analysis, orbital analysis, spin density analysis, and quantum theory of atoms in molecules analysis. Orbital analysis reveals that all four adducts follow a hydrogen atom transfer mechanism for C-H activation. Further, spin density analysis reveals that a higher spin density on the bridging oxygen leads to a lower C-H activation barrier.

Impact of the Copper Second Coordination Sphere on Catalytic Performance and Substrate Specificity of a Bacterial Lytic Polysaccharide Monooxygenase.

Lytic polysaccharide monooxygenases (LPMOs) catalyze the oxidative cleavage of glycosidic bonds in recalcitrant polysaccharides, such as cellulose and chitin, using a single copper cofactor bound in a conserved histidine brace with a more variable second coordination sphere. Cellulose-active LPMOs in the fungal AA9 family and in a subset of bacterial AA10 enzymes contain a His-Gln-Tyr second sphere motif, whereas other cellulose-active AA10s have an Arg-Glu-Phe motif. To shine a light on the impact of this variation, we generated single, double, and triple mutations changing the His216-Gln219-Tyr221 motif in cellulose- and chitin-oxidizing MaAA10B toward Arg-Glu-Phe. These mutations generally reduced enzyme performance due to rapid inactivation under turnover conditions, showing that catalytic fine-tuning of the histidine brace is complex and that the roles of these second sphere residues are strongly interconnected. Studies of copper reactivity showed remarkable effects, such as an increase in oxidase activity following the Q219E mutation and a strong dependence of this effect on the presence of Tyr at position 221. In reductant-driven reactions, differences in oxidase activity, which lead to different levels of in situ generated H2O2, correlated with differences in polysaccharide-degrading ability. The single Q219E mutant displayed a marked increase in activity on chitin in both reductant-driven reactions and reactions fueled by exogenously added H2O2. Thus, it seems that the evolution of substrate specificity in LPMOs involves both the extended substrate-binding surface and the second coordination sphere.

Thermal State Effects on Potential Augmentation of the Ampacity of a Medium Voltage Underground Cable in Power Distribution: A Case Study

Thermal State Effects on Potential Augmentation of the Ampacity of a Medium Voltage Underground Cable in Power Distribution: A Case Study

Experimental study on charging and discharging characteristics of copper finned metal hydride reactor for stationary hydrogen storage applications

With the shift in power generation methods from conventional to renewable, the need for energy storage has increased, and hydrogen as a carrier has great potential. The storage of hydrogen is one of the main obstacles to the effective deployment of the hydrogen economy. Since metal hydride offers a higher energy density than conventional methods, it can potentially be used to store and deliver hydrogen. Also, the metal hydride hydrogen storage system is the primary element of the energy storage system that connects hydrogen production and consumption. Therefore, the present study is focused on the development and testing of a metal hydride reactor. In the present experimental study, 9 kg of La0.7Ce0.1Ca0.3Ni5 is loaded in a single tube copper finned reactor attached to an external jacket, and the charging and discharging characteristics related to hydrogen storage are analysed along with variations in its thermal performance under various operating conditions. Also, the effect of HTF temperature on the hydrogen release performance of the copper finned reactor is studied under constant discharge pressure and constant discharge flow rate. Further, a comparison has been made between the copper and aluminium finned reactors. This fabricated copper finned reactor attained volumetric and gravimetric storage densities of 21.78 kg per m3 of H2 and 0.77%, respectively. The results indicated that La0.7Ce0.1Ca0.3Ni5 filled within the copper finned reactor stores 1.45 wt.% (130.7 g) of hydrogen in 680 s, corresponding to 25 bar feed gas pressure. At the HTF temperature of 60 °C, the copper-finned reactor discharged 1.42 wt.% (127.3 g) of hydrogen in 1450 s, showing the release of 98% of the stored mass of hydrogen. Further, the developed copper finned MH reactor could supply hydrogen at a constant rate of 13 lpm with a capability of 90% discharge even at a discharge temperature of 30 °C. Beside this, the comparative results showed that adding copper fins showed a considerable improvement over aluminium fins during discharging compared to the charging process. The copper-finned reactor consumed 20.9% and 23.6% less time to release 1 wt.% of hydrogen than the aluminium-finned reactor at discharge temperatures of 40 °C and 50 °C, respectively.

Cu-doped polymeric carbon nitrides: structural and electronic properties and sensitivity to flue gas

The global warming of the Earth and its adverse effects on the climate system are among the greatest challenges that humanity faces today and one way to mitigate their development is to control the emissions of greenhouse gases, which can be done with the utilization of suitable adsorbent materials. Recently, polymeric carbon nitrides (PCN) doped with single or geminal copper atoms were experimentally obtained and found to be interesting for catalytic applications. In this work, we study the electronic properties of the bare and copper-containing PCN materials and analyse their potential for sensing or adsorption/separation applications of main constituents of flue gas. Our results indicate that Cu4PCN is a semiconductor with a band gap energy of 1.43 eV, which can be reduced by adsorbing flue gas molecules. Many of these chemisorb, with adsorption energies up to -0.64 eV, and all of them become negatively charged, by up to -0.35 e. The Cu4PCN surface is especially sensitive to NO, NH3, SO2 and SO3, which display some of the strongest adsorptions and charge transfers, along with the most significant changes in the band gap of Cu4PCN, changing its conductivity and allowing detection.

Pockels Effect of Interfacial Water on a Mono-Electrode Induced by Current Parallel to the Electrode Surface

When an electric field is applied between two electrodes facing each other immersed in a liquid, the interfacial Pockels effect, a refractive index change proportional to the electric field, occurs in the electric double layer at the liquid–electrode interface. Here, we report that the Pockels effect of interfacial water can be observed even when an electric field is applied parallel to the surface of a “single” electrode in an electrolyte solution. This is a non-trivial result since the electric field parallel to the interface should not cause a broken spatial inversion symmetry, which is required for the Pockels effect. The Pockels signal was detected as a change in the transmitted light intensity due to the field-induced spectral shift of the interference fringes of the transparent conductive oxide electrode layer on a glass substrate. The magnitude of the signal increased as it approached the ends of the electrode, and the sign reversed across the center of the electrode. The electric field distribution calculated from the interfacial potential difference due to the in-plane parallel current showed that an electric field perpendicular to the interface was induced, whose distribution was consistent with the position dependence of the Pockels signal. A similar phenomenon was also observed for a single copper electrode, confirming that this is a universal effect.

Influence of surface structure and tube material on the condensation heat transfer coefficient of propane on horizontal single tubes and in tube bundles

The condensation heat transfer of propane on the outside of single horizontal tubes and in tube bundles was investigated by determining the condensation heat transfer coefficient αcond in a newly designed experimental setup. To study the influence of different surface structures and tube materials, experiments were conducted with a smooth tube, finned tubes with various fin densities and heights, and a high-performance condensation tube at vapor temperatures of 30 and 40 °C and varying heat flux densities. In addition, the influence of inundation on αcond was systematically investigated by varying the mass flow of liquid condensate at heat flux densities of 20 and 60 kW·m−2. The experimental setup was successfully validated using smooth tubes by a comparison of the resulting αcond with literature data and Nußelt's film theory. For the single copper tubes with fin densities from 19 to 48 fins per inch, αcond increased and was by factors of 9 to 21 larger than for the smooth tube at the same heat flux density. Investigations of the inundation effect have shown that the additional condensate can lead to an increasing condensate film thickness, which decreases αcond due to its increased thermal resistance, and/or can lead to turbulences in the condensate film, which increases αcond. The interplay of the two effects depends highly on the surface geometry. An increasing fin height always enhanced αcond, whereas a lower thermal conductivity of the tube material leads to a smaller αcond.

Atomic Force Microscopy (AFM) Tip based Nanoelectrode with Hydrogel Electrolyte and Application to Single-Nanoparticle Electrochemistry

<p>An unconventional fabrication technique of nanoelectrode was developed using atomic force microscopy (AFM) and hydrogel. Until now, the precise control of electroactive area down to a few nm<sup>2</sup> has always been an obstacle, which limits the wide application of nanoelectrodes. Here, the nanometer-sized contact between the boron-doped diamond (BDD) as conductive AFM tip and the agarose hydrogel as solid electrolyte was well governed by the feedback amplitude of oscillation in the non-contact mode of AFM. Consequently, this low-cost and feasible approach gives rise to new possibilities for the fabrication of nanoelectrodes. The electroactive area controlled by the set point of AFM was investigated by cyclic voltammetry (CV) of the ferrocenmethanol (FcMeOH) combined with quasi-solid agarose hydrogel as an electrolyte. Single copper (Cu) nanoparticle was deposited at the apex of the AFM tip using this platform whose electrocatalytic activity for nitrate reduction was then investigated by CV and Field Emission-Scanning Electron Microscopy (FE-SEM), respectively.</p>