Copper Oxide Nanofibers Research Articles

Copper oxide nanofibers obtained by solution blow spinning as catalysts for oxygen evolution reaction

In this work, we report copper oxide nanofibers (CuO – N) synthesized by Solution Blow Spinning (SBS) for oxygen evolution reaction (OER), and their comparison with a control sample based on a commercial powder (CuO – C). Both materials were characterized by various techniques, including X-ray diffraction (XRD), magnetometry, scanning electron microscopy (SEM), and spectroscopy (Fourier transform infrared (FT-IR), Raman and X-ray photoelectron (XPS)) to determine the purity, microstructural and surface chemical properties. Subsequently, the performance of copper oxide catalysts in a 1.0 M KOH solution was investigated. Copper oxide with nanofiber morphology (CuO – N) exhibited a small overpotential of 385 mV @ 10 mA cm−2 and a Tafel coefficient of only 76 mV dec−1, i.e., fast kinetics for water splitting, a result that is modulated by oxygen vacancies (O2/O1 = 0.83). The oxygen vacancies are due to the presence of Cu1+ in the lattice. The analyses of the magnetization measurements at 5 K suggest a larger amount of Cu1+ in sample CuO – N. Therefore, this work sheds light on how to design low-cost nanofibrous catalysts based on abundant transition metals in the earth's crust by SBS, an economical and scalable technique, which is promising for energy applications.

Charge transfer effects and O2- vacancies in pure CuO nanofibers and enriched with 3.0% Mn

This research shows the relationship between oxygen vacancies and the charge transfer effects generated from the synthesis process using the electrospinning method in an uncontrolled atmosphere for copper oxide nanofibers (CuO NFs) pure and enriched with 3.0% Mn. The thermal measurements obtained through TGA-DSC allowed finding the calcination temperature and obtaining the tenorite structure with monoclinic phase at 700 °C. In addition, the combination of x-ray photoelectron spectrum (XPS) with the multiplet calculation using Cowan's codes suggests that the charge transfer effects play an important role in CuO NFs. After XPS analysis was possible to determine the presence of oxygen vacancies (Vo) and oxygen adsorbed (Ao) in the XPS O 1s region placed at 532 eV. The synthesized materials show a mixture of oxides, and a single oxidation state for Cu3+ in a superlattice according to the selected area electron diffraction (SAED) analysis. Finally, the CuO NFs enriched with 3.0% show the presence of Mn4+ and Mn3+ according to the XPS Mn 2p region analysis.

Aluminum-Doped Mesoporous Copper Oxide Nanofibers Enabling High-Efficiency CO2 Electroreduction to Multicarbon Products

Copper is the most promising catalyst for the electrocatalytic conversion of CO2 into multicarbon (C2+) products but it is often plagued by low selectivity and productivity. Here, we report that aluminum (Al)-doped mesoporous copper oxide nanofibers (Cu-Al MONFs) can exhibit excellent performance in the electrocatalytic reduction of CO2 to C2+ products, with the remarkable C2+ Faradaic efficiency of 76.4% at a high current density of 600 mA cm–2. In sharp contrast, the comparative CuO nanofibers exhibit extremely severe hydrogen evolution (FE up to ∼70%) and limited C2+ products under the same condition. Detailed investigations indicate that the introduction of Al not only induces the formation of a mesoporous structure during the etching process but also adjusts the electronic structure of Cu via doping, which optimize the intermediate binding and C–C coupling on the Cu-Al MONFs. This work provides new inspiration for exploring high-performance Cu-based materials for electrocatalytic reduction of CO2.

Research Report on the Application of MEMS Sensors Based on Copper Oxide Nanofibers in the Braking of Autonomous Vehicles.

Herein, we report a novel nanofiber as a humidity sensor applied to autonomous vehicles. We prepared copper oxide nanofibers by electrospinning, characterized the obtained materials by XRD, SEM, and TEM, and fabricated MEMS sensors based on copper oxide nanofibers. The humidity sensitivity performance of the sensor was tested in different humidity environments. We found that the MEMS humidity sensor based on copper oxide nanofibers can detect the change of humidity in the environment over a large humidity range. Its fast response/mixing speed (1 s), good stability, and sensitivity make it to fully adapt to the high speed of the car.

Engineered CuO Nanofibers with Boosted Non-Enzymatic Glucose Sensing Performance

Developing biosensors with advanced nanomaterial is crucial to enhance the sensing performance of the as-fabricated biosensors. Herein, we engineered copper(II) oxide (CuO) nanofibers using a hydrothermal route in a four-neck flask. The structural and morphological properties of as-engineered CuO nanofibers were analysed using an X-ray diffractometer, field-emission scanning, and transmission electron microscopes. The results indicated, CuO nanofibers bear nanosized diameters and length is in the order of micrometers. These CuO nanofibers were utilized to fabricate non-enzymatic biosensors (Nafion/CuO nanofibers/GCE (glassy carbon electrode)) for enhanced glucose detection and the sensing performance of the biosensors were evaluated using cyclic voltammetry (CV) technique in sodium hydroxide buffer. Employing engineered CuO nanofibers as a non-enzymatic material led fabricated biosensor to achieve high sensitivity of 483.10 μMmM–1cm–2, with the lower detection limit (200 nM) and 0.10–10.85 mM linear detection range. Further, the fabricated biosensor showed good reproducibility, excellent selectivity, cyclic and long-time storage stabilities. This work presents a simple hydrothermal technique to prepare CuO nanofibers in large quantity, demonstrating cost-effective synthesis for non-enzymatic biosensor fabrications and many other applications.

High-Performance Supercapacitor with Faster Energy Storage and Long Cyclic Life Based on CuO@MnO2 Nano-Core–Shell Array on Carbon Fiber Surface

Supercapacitors are a new type of energy storage device, receiving wide attention of researchers in recent years. The electrode material is the core part of the supercapacitor and therefore has higher research value. In this paper, we report an efficient preparation of electrode based on CuO@MnO2 core–shell nanoarray structure and supercapacitor with rapid charge and discharge and long cycle life. First, the surface of the carbon fiber (CF) is electrochemically deposited with a uniform layer of copper (Cu). Second, after in situ chemical treatment on the surface of the Cu layer, copper hydroxide (Cu(OH)2) nanofibers grow and then are converted into copper oxide (CuO) nanofibers. This is the first time that Cu(OH)2 nanofibers have been grown in situ on the surface of CF. Finally, a layer of MnO2 nanocoating grows in situ on the surface of CuO nanofibers to form the CuO@MnO2 core–shell structure. The supercapacitor exhibits excellent charge and discharge rates, taking 4.86 s at a current density of 7 A·g–1, and much shorter than other materials. In addition, it has good capacity retention (96.81%) after 5000 cycles and reaches a maximum energy density of 21.32 Wh·kg–1 at a power density of 7.20 kW·kg–1. Because the prepared electrode material based on the CuO@MnO2 core–shell structure has a faster charge and discharge rate, excellent cycle stability, and high energy density, it will have great application prospects in fields such as spherical triboelectric nanogenerator in the future.

Electrospun copper oxide nanofibers and catalysis for combustion of ammonium perchlorate

Copper oxide (CuO) nanofibers were successfully prepared by electrospinning and subsequent heat treatment. The chemical composition and morphology of the fibers were characterized by SEM, XRD and EDS. Beaded nanofibers with 100nm in diameter were prepared by simple electrospinning and calcining. The catalytic effect of CuO nanofibers on the combustion of ammonium perchlorate (AP) was investigated by TG and DTA. The results showed that the decomposition temperature of AP shifted by 101.9 °C to the low temperature and the catalytic efficiency was very high. This is mainly attributed to the higher surface to volume ratio of beaded copper oxide nanofibers compared with smooth nanofibers and spherical nanoparticles. The results suggest that the electrospinning of CuO nanofibers is a promising one-dimensional nanometer material in the field of propellant catalysis.

Mechanism and experimental evidence of rapid morphological variant of copper oxide nanostructures by microwave heating

In this work, the formation mechanisms under rapid microwave radiation of copper oxide nanofibers and copper oxide nanoparticles were proposed. The copper oxide nanofibers were synthesized by using only pure copper powders. Whereas, ethanol addition in pure copper powders significantly influenced nucleation and morphological formation of the copper oxide nanoparticles. Both nanofibers and nanoparticles were determined by X-ray diffractometer (XRD) showing a mixture of Cu2O and CuO phases. The mixed structures were clearly confirmed by transmission electron microscope (TEM). The copper oxide nanofiber diameters were in the range of 500–5,500 nm with an average length of about 2.5 cm and a circular cylindrical shape and smooth surface. The nanoparticles showed a spherical shape with homogeneous size in the diameter range of 80–120 nm. This report further investigated a formation mechanism using experimental results. The study showed that the formation could be attributed to surface reactions of ethanol in polar characteristic way that accumulated thermal into Cu powders.

Fabrication and characterization of Zn doped CuO nanofiber using newly designed nanofiber generator for the photodegradation of methylene blue from textile effluent

Abstract High aspect ratio, Zn doped copper oxide (Zn-CuO) nanofibers have been fabricated employing a newly designed electrospun coating unit using copper acetate, sodium hydroxide and polyethylene glycol in aqueous state. The prepared Zn doped copper oxide (Zn-CuO) nanofibers were sintered at 400 °C, 500 °C and 600 °C separately and characterized using X-ray diffraction XRD, Fourier transformation infrared spectroscopy FT-IR, scanning electron microscopy SEM, energy dispersive spectroscopy EDS. The average crystallite size was in the range of 28 nm to 30 nm. Optical properties of Zn-CuO nanofibers were analyzed using UV-DRS studies which showed a blue shift in the absorption band. An increase in band gap with the increase in postannealing temperature was observed due to the blue shift in absorption edge of CuO causing enhanced photodegradation. The catalytic properties of the CuO nanofibers were tested using methylene blue in aqueous medium. The influences of parameters responsible for high photodegradation were optimized and the rate of the photodegradation process was calculated using photodegradation kinetics. The reusability test was conducted to find the stability of the fabricated Zn-CuO nanofibers.

Synthetic Mechanism Discovery of Monophase Cuprous Oxide for Record High Photoelectrochemical Conversion of CO2 to Methanol in Water.

Precise control of the oxidation state of transition-metal oxides, such as copper, is important for high selectivity of CO2 reduction in an aqueous condition to compete with the reduction of water. The phase of copper oxide nanofibers was controlled by predictive synthesis, which controls the nanoscale gas-solid reaction by considering thermodynamics and kinetics. The driving force of the phase transformation between the different oxidation states of copper oxide is calculated by comparing the Gibbs free energy of each of the oxidation states. From the calculation, the kinetically processable window for the fabrication of Cu2O in which monophase Cu2O can be fabricated in a reasonable reaction time scale is discovered. Herein, we report the monophase Cu2O nanofiber photocathode, which photoelectrochemically converted CO2 into methanol with over 90% selectivity in an aqueous electrolyte, and a hierarchical structure is developed to optimize the photoactivity and stability of the electrode. Our work suggests a rational design of the calcination strategy for precisely controlling the oxidation states of transition metals that can be applied to various applications in which the phase of the materials plays an important role.

Green Synthesis of 1,1'-Carbonyldiimidazole Using Copper Oxide Nanofiber as a Heterogeneous Catalyst.

Poly(vinyl pyrrolidone) (PVP)/copper oxide composite nanofibers were prepared by electrospinning technique using PVP and copper acetate as precursors and calcinated at high temperature to yield polymer free, phase pure copper oxide nanofibers (CuO NFs). The powder X-ray diffraction (XRD) pattern, transmission electron microscopic (TEM) images and selected area electron diffraction pattern (SAED) results showed that the calcinated CuO NFs were crystalline with 166 nm diameter and monoclinic in phase. From the catalytic application point of view, the newly prepared electrospun CuO NFs were tested for N-arylation of imidazole using aryl halides. To our surprise, 1,1'-carbonyldiimidazole (CDI) was obtained under the conditions of air and nitrogen atmosphere. Furthermore, the same product CDI was obtained from the reactions where in no aryl halide was involved but with imidazole alone as substrate. Our methodology to prepare CDI is free from the use of toxic phosgene as carbonyl source, as reported earlier. Hence, the present process possesses some advantages such as green and cost effective alternate for the existing synthesis method.

Effects of Mixed-Phase Copper Oxide Nanofibers in ZnO Dye-Sensitized Solar Cells on Efficiency Enhancement

Effects of Mixed-Phase Copper Oxide Nanofibers in ZnO Dye-Sensitized Solar Cells on Efficiency Enhancement

Poly-l-cysteine/electrospun copper oxide nanofibers-zinc oxide nanoparticles nanocomposite as sensing element of an electrochemical sensor for simultaneous determination of adenine and guanine in biological samples and evaluation of damage to dsDNA and DNA purine bases by UV radiation

A new nanocomposite film constructed of poly-l-cysteine/zinc oxide nanoparticles–electrospun copper oxide nanofibers (PLC/ZnO-NPs–CuO-NFs) was prepared on the surface of the graphite electrode (GE). The novel electrode was successfully applied for the simultaneous determination of guanine (G) and adenine (A), two of the most important components of DNA and RNA. The PLC/ZnO-NPs–CuO-NFs/GE enhanced the anodic peak currents of the purine bases conspicuously and could determine them sensitively and separately in 0.1 M phosphate buffer solution at the physiological pH (7.0). The synthesized nanofibers, nanoparticles and nanocomposite were characterized by different methods such as Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), scanning electron microscopy (SEM), field emission scanning electron microscopy (FE-SEM), atomic force microscopy (AFM), X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDS). Under the optimum operating conditions, linear calibration curves were obtained in the range of 0.05–6.78 and 0.01–3.87 μM with a detection limit of 12.48 and 1.25 nM for G and A, respectively. The proposed method was applied to quantify A and G in three different DNA samples with satisfactory results. In addition, damage to human blood double-stranded DNA (dsDNA) and DNA purine bases (liberated in previously hydrolyzed human blood dsDNA) caused by UV-C and UV-B were evaluated. The results demonstrated that the proposed biosensing platform not only provides a novel and sensitive approach to detecting DNA damage, but also can be used for simultaneous determination of purine bases and major products of DNA oxidative damage.

Nano-textured copper oxide nanofibers for efficient air cooling

Ever decreasing of microelectronics devices is challenged by overheating and demands an increase in heat removal rate. Herein, we fabricated highly efficient heat-removal coatings comprised of copper oxide-plated polymer nanofiber layers (thorny devil nanofibers) with high surface-to-volume ratio, which facilitate heat removal from the underlying hot surfaces. The electroplating time and voltage were optimized to form fiber layers with maximal heat removal rate. The copper oxide nanofibers with the thorny devil morphology yielded a superior cooling rate compared to the pure copper nanofibers with the smooth surface morphology. This superior cooling performance is attributed to the enhanced surface area of the thorny devil nanofibers. These nanofibers were characterized with scanning electron microscopy, X-ray diffraction, atomic force microscopy, and a thermographic camera.

CuO Nanofibers Immobilized on Paraffin-Impregnated Graphite Electrode and its Application in the Amperometric Detection of Glucose

1-D nanostructures are promising materials for development of electrochemical devices offering benefits such as fast electron transfer rates and large surface areas. Copper oxide nanofibers (CuO-NFs) synthesized by electrospinning technique and subsequent thermal treatment, were used to modify paraffin-impregnated graphite electrode (PIGE) for a sensitive non-enzymatic glucose detection. The structure and morphology of CuO-NFs were characterized by scanning electron microscopy and transmission electron microscopy. The electrocatalytic activity towards glucose oxidation was evaluated by cyclic voltammetry and chronoamperometry. The results reveal a wide linear response to glucose ranging from 1.0 × 10-6 to 1.93 × 10-3mol L-1 (R2 = 0.9927). The limit of detection was 0.39 × 10-6 mol L-1 (LOD = 3σ/s). The high aspect ratio of the nanofibers arranged in a three-dimensional network structure significantly enhances the electron transfer process. The electrode preparation is simple and rapid execution, and more importantly the graphite rod is relative low-cost and easy to achieve surface renewal for reusability.

Electrospun copper oxide nanofibers as infrared photodetectors

Copper oxide (CuO) nanofibers (NFs) were synthesized in the form of dense mesh via electrospinning technique and evaluated as infrared (IR) photodetectors. When illuminated with an IR (808 nm) laser diode with a power density of 10–40 mW/cm2, significant photocurrent with a response time as low as 1–2 ms was observed. Such efficient photodetection behavior of electrospun CuO NFs was attributed to their unique morphology defined by tiny crystalline domains attached together in a linear 1D fashion offering very high surface-to-volume ratio and efficient electron transport. It was also found that an appropriate thickness of CuO NFs mesh is required for optimizing device responsivity.

High areal capacity, micrometer-scale amorphous Si film anode based on nanostructured Cu foil for Li-ion batteries

We report a feasible design to fabricate micrometer-scale Si films deposited on nanostructured Cu foil as high areal capacity anodes for Li-ion batteries with excellent cycling performance. Nanostructured copper oxides are prepared by anodic oxidation of Cu foil in alkaline solution. The resultant copper oxide nanofibers function as matrix for thick Si films (1–2 μm) loading. Metallic Cu nanofibers are obtained by in-situ electrochemical reduction at low potentials, which work as electrical highways for fast electron transport and a reliable mechanical matrix to accommodate volume changes during lithium–silicon alloy/dealloy processes. The engineered thick Si film anode exhibit both high areal capacity (0.48 mAh cm−2 for 1 μm Si film and 0.6 mAh cm−2 for 2 μm Si film after 200 cycles at 0.225 mA cm−2) and excellent rate capability (0.52 mAh cm−2 at 1.05 mA cm−2 for 2 μm Si film). The 2 μm silicon film electrode is able to recover to the initial value of 1 mAh cm−2 when the current rate is set back to 0.15 mA cm−2 even after cycling at high current rates. The reported concept can be a general method for high-loading-film electrodes, which is industrial scalable and compatible with current battery manufacturing processes.

Tuning the oxidation states and crystallinity of copper oxide nanofibers by calcination

Cu oxide/polyvinyl alcohol (PVA) nanofibers were synthesized by sol–gel and electrospinning technique. The obtained Cu oxide/PVA nanofibers were heated to remove the PVA compound at 673 and 873 K. The ultrafine Cu oxide nanofibers were characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The SEM images showed that the Cu oxide nanofibers were successfully synthesized by electrospinning and calcination and the average diameters of the electrospun Cu/PVA nanofibers were 268.9 ± 97.2 nm. After the nanofibers were calcined at higher temperature than rt, the morphologies of the nanofibers changed. XRD results indicated that the crystalline structure changed from amorphous phase to monoclinic CuO through cubic Cu2O. TEM images also verified the crystal phase of Cu oxide nanofibers. XPS spectra revealed that the thermal oxidation of Cu proceeded during calcination.

Preparation and Characterization of Copper Oxide Nanofibers by Microwave-Assisted Thermal Oxidation

Preparation and Characterization of Copper Oxide Nanofibers by Microwave-Assisted Thermal Oxidation

Binary CuO/Co3O4 nanofibers for ultrafast and amplified electrochemical sensing of fructose

Cobalt oxide-doped copper oxide composite nanofibers (CCNFs) were successfully achieved via electrospinning followed by thermal treatment processes and then exploited as active electrode material for direct enzyme-free fructose detection. The morphology and the structure of as-prepared samples were investigated by X-ray diffraction spectrum (XRD) and scanning electron microscopy (SEM). The electrocatalytic activity of CCNFs films towards fructose oxidation and sensing performances were evaluated by conventional electrochemical techniques. Cyclic voltammetry (CV) and chronoamperometry (I−t) revealed the distinctly enhanced sensing properties towards fructose compared to pure copper oxide nanofibers (CNFs), i.e., showing significantly lowered overpotential of 0.30V, ultrafast (1s) and ultrasensitive (18.988μAmM−1) current response in a wide linear range of 1.0×10−5M to 6.0×10−3M with satisfied reproducibility and stability, which could be ascribed to the synergic catalytic effect of the binary CuO/Co3O4 composite nanofibers and the highly porous three-dimensional network films structure of the CCNFs. In addition, a good selectivity for fructose detection was achieved. Results in this work demonstrated that CCNFs is one of the promising catalytic electrode materials for enzymeless fructose sensor fabrication.