Cu,N codoped carbon nanosheets encapsulating ultrasmall Cu nanoparticles for enhancing selective 1,2-propanediol oxidation

In the selective oxidation of biomass-based 1,2-propanediol(PDO)with oxygen as the terminal oxidant,it is challenging to improve the lactic acid(LA)selectivity for nonnoble metal nanoparticles(NPs)due to their limited oxygen reduction rate and easy C-C cleavage.Given the high economic feasibility of nonnoble metals,i.e.,Cu,in this work,copper and nitrogen codoped porous carbon nanosheets encapsulating ultrafine Cu nanoparticles(Cu@Cu-N-C)were developed to realize highly selective of PDO oxidation to LA.The carbon-encapsulated ultrasmall Cu^(0)NPs in Cu@Cu-N-C have high PDO dehydrogenation activity while N-coordinated Cu(Cu-N)sites are responsible for the high oxygen reduction efficacy.Therefore,the performance of catalytic PDO conversion to LA is optimized by a proposed pathway of PDO→hydroxylacetone→lactaldehyde→LA.Specifically,the enhanced LA selectivity is 88.5%,and the PDO conversion is up to 75.1%in an O_(2)-pressurized reaction system(1.0 MPa O_(2)),superior to other Cu-based catalysts,while in a milder nonpressurized system(O_(2)flow rate of 100 mL min-1),a remarkable LA selectivity(94.2%)is obtained with 39.8%PDO conversion,2.2 times higher than that of supported Au nanoparticles(1%Au/C).Moreover,carbon encapsulation offers Cu@Cu-N-C with strong leaching resistance for better recycling.

Preparation of Cu nanoparticles with ascorbic acid by aqueous solution reduction method

Cu nanoparticles were prepared by reducing Cu2＋ ions with ascorbic acid through aqueous solution reduction method. The effects of solution pH and average size of Cu2O particles on the preparation of Cu nanoparticles were investigated. Cu particles were prepared at pH 3, 5 or 7, with the smallest Cu particles obtained at pH 7. However, Cu particles could not be prepared at pH 9 or 11. The average size of Cu2O particles can affect that of Cu particles. Larger Cu2O particles result in larger Cu particles. In addition, experiments were conducted to explore the reaction process by measuring the X-ray diffraction （XRD） patterns of specimens collected at different time points during the reaction. It was found that Cu（OH）2 was initially formed as a precursor, followed by the formation of Cu2O, which was finally reduced to Cu particles.

Effects of reaction parameters on preparation of Cu nanoparticles via aqueous solution reduction method with NaBH_4

The preparation of Cu nanoparticles by the aqueous solution reduction method was investigated. The effects of different reaction parameters on the preparation of Cu nanoparticles were studied. The optimum conditions for preparing well-dispersed nanoparticles were found as follows: 0.4 mol/L NaBH4 was added into solution containing 0.2 mol/L Cu2+, 1.0% gelatin dispersant in mass fraction, and 1.2 mol/L NH3?H2O at pH 12 and 313 K. In addition, a series of experiments were performed to discover the reaction process. NH3?H2O was found to be able to modulate the reaction process. At pH=10, Cu2+ was transformed to Cu(NH3)42+ as precursor after the addition of NH3?H2O, and then Cu(NH3)42+ was reduced by NaBH4 solution. At pH=12, Cu2+ was transformed to Cu(OH)2 as precursor after the addition of NH3?H2O, and Cu(OH)2 was then reduced by NaBH4 solution.

Preparation and particle size characterization of Cu nanoparticles prepared by anodic arc plasma

Copper nanoparticles were successfully prepared in large scale by means of anodic arc discharging plasma method in inert atmosphere. The particle size, specific surface area, crystal structure, and morphology of the samples were characterized by X-ray diffraction （XRD）, BET equation, transmission electron microscopy （TEM）, and the corresponding selected area electron diffraction （SAED）. The experimental results indicate that the crystal structure of the samples is fcc structure the same as that of the bulk materials. The specific surface area is 11 m^2/g, the particle size distribution is 30 to 90 nm, and the average particle size is about 67 nm obtained from TEM and confirmed from XRD and BET results. The nanoparticles with uniform size, high purity, narrow size distribution and spherical shape can be prepared by this convenient and effective method.

Preparation of Cu nanoparticles with NaBH_4 by aqueous reduction method

Cu nanoparticles were prepared by reducing Cu2＋ ions with NaBH4 in alkaline solution. The effects of NaBH4 concentration and dripping rate on the formation of Cu nanoparticles were studied. The optimum conditions are found to be 0.2 mol/L Cu2＋, solution with pH=12, temperature of 313 K and 1% gelatin as dispersant, to which 0.4 mol/L NaBH4 is added at a dripping rate of 50 mL/min. NH3-H2O is found to be the optimal complexant to form the Cu precursor. A series experiments were conducted to study the reaction process at different time points.

Synthesis of Cu nanoparticles by chemical reduction method

Cu nanoparticles (CuNPs) have been synthesized through an easy route by chemical reduction at room temperature. The Cu^2+ ions were reduced and stabilized with sodium borohydride and polyvinylpyrrolidone, respectively. The effect of the variation of the reducing agent/precursor-salt (RA/PS) ratio on the size and morphology of the CuNPs was evaluated. The synthesized material was studied by ultraviolet-visible (UV-Vis) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The UV-Vis spectra showed a CuNPs plasmon peak at 569 nm and another peak belonging to Cu2O at 485 nm. XRD analysis showed the fcc-Cu phase with a small amount of fcc-Cu2O compound. SEM and TEM studies displayed that small semispherical CuNPs of approximately 7 nm were obtained at the RA/PS ratio of 2.6. The excess of polyvinylpyrrolidone stabilizer played an essential role in preventing CuNPs oxidation. On the other side, Cu2O polyhedral particles with larger sizes up to 150 nm were identified in the RA/PS ratio range of 2.0-1.84. In addition, Cu2O particles having star morphologies with quantum confinement at their tips were obtained at the RA/PS ratio of 1.66.

A Solvothermal Route to Cu_2O Nanocubes and Cu Nanoparticles

Cu2O nanocubes and Cu nanoparticles were prepared by reducing Cu（ Ⅱ ） salt with ethanol as the reducing agent and solvent in the presence of multidentate ligand poly（vinylpyrrolidone） （PVP） under different conditions. The morphologies and the crystalline structures of the products were characterized by using scanning electron microscopy （SEM）, transmission electron microscopy（TEM）, selected-area electron diffraction（ SAED）, and powder X-ray diffraction（XRD）. In particular, the influences of the solvothennal reaction temperature and alkalinity on the products were investigated. A lower temperature and a lower alkali concentration favor the formation of the Cu2O phase, whereas a higher temperature and a higher alkali concentration generally lead to the formation of the Cu phase.

Catalytic transformation of 4-nitrophenol into 4-aminophenol over ZnO nanowire array-decorated Cu nanoparticles

To realize economical and effective removal of hazardous 4-nitrophenol from the environment,we developed an easily recyclable ZnO nanowire array decorated with Cu nanoparticles.Its salix argyracea-shaped structure not only provides a platform to achieve stable and good dispersion of Cu nanoparticles,but also offers a great deal of catalytically active sites.The density functional theory calculations reveal that ZnO and Cu have a very beneficial synergistic effect on their catalytic capability.This synergy is ascribed to the electronic localization occurring at ZnO/Cu interface,which helps improve Cu nanoparticle’s ability to adsorb electro-negatively 4-nitrophenolate ions and to capture hydrogen radicals,thereby accelerating the hydrogen transfer from metal hydride complex to 4-nitrophenol.Benefiting from these characteristics,it exhibits high efficiency and reusability towards the catalytic reduction of waste 4-nitrophenol to valuable 4-aminophenol with a rate constant of 43.02×10^(-3)s^(-1)and an average conversion of 96.5%in 90 s during 10 cycles.This activity is superior to that of most reported noble-or non-noble-metal powder,bulk,coating,and array catalysts,indicating its competitive advantages in cost and efficiency,as well as enticing application prospects.

Exploring the impact of Nafion modifier on electrocatalytic CO_(2) reduction over Cu catalyst

Nafion as a universal polymer ionomer was widely applied for nanocatalysts electrode preparation.However,the effect of Nafion on electrocatalytic performance was often overlooked,especially for CO_(2)electrolysis.Herein,the key roles of Nafion for CO_(2)RR were systematically studied on Cu nanoparticles(NPs)electrocatalyst.We found that Nafion modifier not only inhibit hydrogen evolution reaction(HER)by decreasing the accessibility of H_(2)O from electrolyte to Cu NPs,and increase the CO_(2)concentration at electrocatalyst interface for enhancing the CO_(2)mass transfer process,but also activate CO_(2)molecule by Lewis acid-base interaction between Nafion and CO_(2)to accelerate the formation of^(*)CO,which favor of C–C coupling for boosting C_(2)product generation.Owing to these features,the HER selectivity was suppressed from 40.6%to 16.8%on optimal Cu@Nafion electrode at-1.2 V versus reversible hydrogen electrode(RHE),and as high as 73.5%faradaic efficiencies(FEs)of C_(2)products were achieved at the same applied potential,which was 2.6 times higher than that on bare Cu electrode(~28.3%).In addition,Nafion also contributed to the long-term stability by hinder Cu NPs morphology reconstruction.Thus,this work provides insights into the impact of Nafion on electrocatalytic CO_(2)RR performance.

Modulating p-d orbital hybridization by CuO/Cu nanoparticles enables carbon nanofibers high cycling stability as anode for sodium storage

Carbon nanofibers(CNFs)have been extensively studied as anode materials for sodium-ion batteries due to their high conductivity,large aspect ratio and good electrochemical stability.The low specific capacity and low first cycle efficiency of CNFs,however,have hindered its practical application.Herein,we present a facile strategy to synthesize a novel CNFs decorated with Cu/CuO nanoparticles(Cu-CNFs)using magnetron sputtering method.Cu/CuO nanoparticles were uniformly distributed on the surface of CNFs.According to the density functional theory(DFT)calculation,Cu/CuO nanoparticles d-orbitals and CNFs p-orbitals present hybridization states,and the Na~+adsorption energy of the modified CNFs decreases from-2.14 to-2.97 eV.The Cu-CNFs composites exhibit excellent sodium storage properties,presenting a desirable initial Coulombic efficiency of 76%and a high specific reversible capacity of 300 mAh·g^(-1)at 0.1 A·g^(-1)after 400 cycles.Cu-CNFs anode has excellent cycling stability under high current density,maintaining a high capacity of 150 mAh·g^(-1)at 1 A·g^(-1)after 6000 cycles.Using magnetron sputtering to regulate the electronic structure provides a new thought for improving the electrochemical performance of carbon materials.

Fabrication of Cu_2O@Cu_2O core-shell nanoparticles and conversion to Cu_2O@Cu core-shell nanoparticles in solution

Cu2O@Cu2O core-shell nanoparticles (NPs) were prepared by using solution phase strategy. It was found that Cu2O@Cu2O NPs were easily converted to Cu2O@Cu NPs with the help of polyvinylpyrrolidine (PVP) and excessive ascorbic acid (AA) in air at room temperature, which was an interesting phenomenon. The features of the two kinds of NPs were characterized by XRD, TEM and extinction spectra. Cu2O@Cu NPs with different shell thicknesses showed wide tunable optical properties for the localized surface plasmon (LSP) in metallic Cu. But Cu2O@Cu2O NPs did not indicate this feature. FTIR results reveal that Cu+ ions on the surface of Cu2O shell coordinate with N and O atoms in PVP and are further reduced to metallic Cu by excessive AA and then form a nucleation site on the surface of Cu2O nanocrystalline. PVP binds onto different sites to proceed with the reduction utill all the Cu sources in Cu2O shell are completely assumed.

Direct growth of special-shape graphene on different templates by remote catalyzation of Cu nanoparticles

A novel method avoiding the complex transfer process is proposed to directly grow low-defect and few-layer graphene on different insulating substrates（SiO2, Al2O3, etc.） by remote catalyzation of Cu nanoparticles（NPs） using ambient pressure chemical vapor deposition（APCVD）. The insulating substrates with special structure are used as templates to grow wrapped graphene sheets with special shapes.Hollow graphene species are obtained by removing the substrates. The prime feature of the proposed method is using Cu NPs as catalyst rather than metal foils. The Cu NPs play an important role in the remote catalyzation during the nucleation of graphene. This method can improve the quality and relatively decrease the growth temperature of the graphene on the insulating substrates, which displays the great potential of APCVD direct growth of graphene on dielectric substrates for electronic and photovoltaic applications.

Synthesis of Cu_2ZnSnS_4 thin film from mixed solution of Cu_2SnS_3 nanoparticles and Zn ions

The Cu2ZnSnS4 thin film was prepared by a facile solution method without vacuum environment and toxic substance. The formation mechanism of the film was studied by transmission electron microscopy (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and Raman scattering measurements. Through cyclic voltammetry and photo-electricity tests, the electrocatalytic activity of the prepared film as the counter electrode of dye-sensitizedsolar cell was also studied. The results show that the mixed precursor solution mainly consists of Cu2SnS3 nanoparticles and Zn ions.After 550 °C annealing process on the precursor film prepared from the mixed solution, Cu2ZnSnS4 thin film is obtained. Besides, itis found that the prepared Cu2ZnSnS4 thin film has the electrocatalytic activity toward the redox reaction of I3?/I? and the dye-sensitized solar cell with the prepared Cu2ZnSnS4 thin film as the counter electrode achieves the efficiency of 1.09%.

Recent progress on copper catalysts with different surface states for CO_(2)electroreduction

The electrochemical carbon dioxide reduction reaction(eCO_(2)RR),which converts CO_(2)into various hydrocarbons or alcohols,has been extensively researched because it promises a sustainable energy economy.However,only copper(Cu)can currently achieve stable and efficient hydrocarbon conversion in the eCO_(2)RR.Therefore,understanding the catalytic mechanisms and summarizing the research progress on synthesis strategies of Cu catalysts are essential for the eCO_(2)RR.This paper reviews Cu catalysts with different surface states of Cu catalysts:oxide-derived Cu,Cu nanoparticles,Cu single atoms,and Cu nanoclusters.It then reviews the development and progress of different Cu-catalyst preparation methods in recent years,focusing on the activity and selectivity of materials.Besides revealing the tendencies of catalytic selection and deep reactive mechanisms of Cu catalysts with four different surface states,this review can guide the subsequent construction of catalysts and provides an understanding of catalytic mechanisms.

Single Step Microwave Assisted Synthesis and Antimicrobial Activity of Silver, Copper and Silver-Copper Nanoparticles

Copper and silver nanoparticles were synthesized and characterized in two minutes at 175°C in a one-step synthesis using a modified polyol (ethylene glycol) method and a microwave heating process. We successfully synthesized spherical Silver (Ag) and Copper nanoparticles (CuNP) with a crystallite size of less than 10 nm, as well as irregular silver-copper nanoparticles (AgCuNP) with a crystallite size of less than 15 nm, as confirmed by X-Ray Diffraction (XRD) and High-Resolution Transmission Electron Microscopy (HRTEM). The successful synthesis of AgCuNP with 1:1 molar ratio and constituted by 51.74% of copper and 48.26% of silver was corroborated using the Energy Dispersive X-ray (EDX) mapping technique. The AgNP and AgCuNP exhibited more stability in suspension, in comparison to CuNP, as observed by continuously monitoring the absorbance with UV-Vis spectroscopy for 12 days. Furthermore, the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of AgNP, CuNP, and AgCuNP were determined, against Gram-negative and Gram-positive bacteria, and yeast. The obtained MIC and MBC values indicate that AgCu nanoparticles exhibited bactericidal properties greater than its constituents. On the contrary, antifungal activity of AgCuNP against yeast was not observed.

Zr（Ⅳ） surface sites determine CH3OH formation rate on Cu/ZrO2/SiO2-CO2 hydrogenation catalysts

Cu/ZrO2/SiO2 are efficient catalysts for the selective hydrogenation of CO2 to CH3OH. In order to understand the role of ZrO2 in these mixed-oxides based catalysts, in situ X-ray absorption spectroscopy has been carried out on the Cu and Zr K-edge. Under reaction conditions, Cu remains metallic, while Zr is present in three types of coordination environment associated with 1) bulk ZrO2, 2) coordinatively saturated and 3) unsaturated Zr(Ⅳ) surface sites. The amount of coordinatively unsaturated Zr surface sites can be quantified by linear combination fit of reference X-Ray absorption near edge structure (XANES) spectra and its amount correlates with CH3OH formation rates, thus indicating the importance of Zr(Ⅳ) Lewis acid surface sites in driving the selectivity toward CH3OH. This finding is consistent with the proposed mechanism, where CO2 is hydrogenated at the interface between the Cu nanoparticles that split H2 and Zr(Ⅳ) surface sites that stabilizes reaction intermediates.

Fabrication and photocatalytic properties of Cu_2S/T-ZnO_w heterostructures via simple polyol process

The Cu2S/tetrapod-like ZnO whisker（T-ZnOw） heterostructures were successfully synthesized via a simple polyol process employing the poly（vinyl pyrrolidone）（PVP） as a surfactant.The as-prepared heterostructures were characterized by X-ray diffraction（XRD）,field emission scanning electron microscopy（FESEM）,X-ray photoelectron spectroscopy（XPS） and Fourier transform infrared（FTIR）.The photocatalytic properties of Cu2S/T-ZnOw nanocomposites synthesized with different PVP concentrations were evaluated by photodegradation of methyl orange（MO） under UV irradiation.The results show that the Cu2S/T-ZnOw nanocomposites exhibit remarkable improved photocatalytic property compared with the pure T-ZnOw.The sample prepared with 3.0 g/L PVP shows an excellent photocatalytic property and the highest photodegradation rate of MO is 97% after UV irradiation for 120 min.Besides,the photocatalytic activity of the photocatalyst has no evident decrease even after four cycles,which demonstrates that the Cu2S/T-ZnOw photocatalyst exhibits an excellent photostability.Moreover,the photocatalytic mechanism of the Cu2S/T-ZnOw nanocomposites was also discussed.

Optical and electrical characterizations of nanoparticle Cu_2S thin films

Copper sulfide thin films are deposited onto different substrates at room temperature using the thermal evaporation technique. X-ray diffraction spectra show that the film has an orthorhombicchalcocite （7-Cu2S） phase. The atomic force microscopy images indicate that the film exhibits nanoparticles with an average size of nearly 44 nm. Specrtophotometric measurements for the transmittance and reflectance are carried out at normal incidence in a spectral wavelength range of 450 nm-2500 nm. The refractive index, n, as well as the absorption index, k is calculated. Some dispersion parameters are determined. The analyses of el and e2 reveal several absorption peaks. The analysis of the spectral behavior of the absorption coefficient, c~, in the absorption region reveals direct and indirect allowed transitions. The dark electrical resistivity is studied as a function of film thickness and temperature. Tellier＇s model is adopted for determining the mean free path and bulk resistance.

Magnetic properties of DNA-templated Co/Cu naonoparticle chains

According to ultraviolet （UV）-vis absorption spectra recorded in the DNA metallization process, DNA-templated Co/Cu binary nanoparticle chains are fabricated by incubating genome DNA of paralichthys olivaceus muscle in CoCl2 and CuCl2 mixture solution for 20 hours and reducing the complex for 2 hours. Transmission electron microscopy observation indicates that Co and Cu nanoparticles with 20 nm in diameter were randomly dispersed on the DNA template. The superconducting quantum interference device （SQUID） measurements display that the magnetic interaction between cobalt particles is greatly decreased by the copper particle. With increasing copper content, the coercivity of the systems enhance from 9 Oe to 100 Oe （1 Oe=79.5775 A/m）.

Tandem catalysis of Cu/Ni multi-sites promotes oxygen reduction reaction

The special electronic characteristics and high atom usage efficiency of metal-nitrogen-carbon(M-N-C)materials have made them extremely attractive for oxygen reduction reactions(ORRs).However,it is inevitable that hydrogen peroxide(H_(2)O_(2))will be formed via the two-electron pathway in ORRs.Herein,the Cu nanoparticles(NPs)have been encapsulated into Ni doped hollow mesoporous carbon spheres(Ni-HMCS)to reduce the generation of H_(2)O_(2)in ORR.Electrochemical tests confirm that the introduction of Cu NPs improves the ORR performance greatly.The obtained Cu/Ni-HMCS exhibits a half-wave potential of 0.82 V vs.reversible hydrogen electrode and a limited current density of 5.5 mA cm^(-2),which is comparable with the commercial Pt/C.Moreover,Cu/Ni-HMCS has been used in Zn-air battery,demonstrating a high power density of 161 mW cm^(-2)and a long-term recharge capability(50 h at 5 mA cm^(-2)).The theoretical calculation proposes a tandem catalysis pathway for Cu/Ni multi-sites catalysis,that is,H_(2)O_(2)released from the Ni-N_(4)and Cu-N_(4)sites migrates to the Cu(111)face,on which the captive H_(2)O_(2)is further reduced to H_(2)O.This work demonstrates an interesting tandem catalytic pathway of dual-metal multi-sites for ORR,which provides an insight into the development of effective fuel cell electrocatalysts.