Copper Oxide Nanowire Arrays Research Articles

A core–shell copper oxides-cobalt oxides heterostructure nanowire arrays for nitrate reduction to ammonia with high yield rate

Electrochemical nitrate reduction to ammonia (NRA) can realize the green synthesis of ammonia (NH3) at ambient conditions, and also remove nitrate contamination in water. However, the current catalysts for NRA still face relatively low NH3 yield rate and poor stability. We present here a core–shell heterostructure comprising cobalt oxide anchored on copper oxide nanowire arrays (CuO NWAs@Co3O4) for efficient NRA. The CuO NWAs@Co3O4 demonstrates significantly enhanced NRA performance in alkaline media in comparison with plain CuO NWAs and Co3O4 flocs. Especially, at −0.23 V vs. RHE, NH3 yield rate of the CuO NWAs@Co3O4 reaches 1.915 mmol h−1 cm−2, much higher than those of CuO NWAs (1.472 mmol h−1 cm−2), Co3O4 flocs (1.222 mmol h−1 cm−2) and recent reported Cu-based catalysts. It is proposed that the synergetic effects of the heterostructure combing atom hydrogen adsorption and nitrate reduction lead to the enhanced NRA performance.

Vertical copper oxide nanowire arrays attached three-dimensional macroporous framework as a self-supported sensor for sensitive hydrogen peroxide detection

A hierarchical nanostructure consisting of uniform copper oxide nanowires vertically grown on three-dimensional copper framework (CuO NWs/3D-Cu foam) was prepared by a two-step synthetic process. The uniform CuO NWs anchored onto the 3D foam exhibited outstanding electrocatalytic activity towards hydrogen peroxide reduction due to the unique one‐dimensional direction with its excellent catalytic activity and large surface area of 3D substrate, which enhanced electroactive sites and charge conductivity. As a result, a wide linear detection range of 1 µM–1 mM, good sensitivity of 8.87 µA/(mM ⋅ cm2), low detection limit of 0.98 µM, and rapid response time of 5 s to hydrogen peroxide were achieved under a working potential of −0.4 V in phosphate buffer solution (pH of 7.4). In addition, the CuO NWs/3D-Cu foam material showed excellent selectivity to hydrogen peroxide and good resistance against poisonous interferents, including ascorbic acid, dopamine, urea, uric acid, and potassium chloride. Furthermore, the CuO NWs/3D-Cu foam presented good reproducibility, stability, and accurate detection for hydrogen peroxide in real sample; therefore, it may be considered to be a potential free-standing hydrogen peroxide sensor in practical analysis applications.

Copper Oxide-Based Photocathodes and Electrocatalysts for the (Photo)Electrochemical Reduction of Protons and Carbon Dioxide

The use of renewable electricity to drive chemical reactions is an approach to storing the energy from intermittent sources (solar, wind) in the form of chemical bonds. Combining photoabsorber and electrocatalytic components into integrated devices, we developed copper oxide-based photocathodes for proton reduction to hydrogen (1,2), as well as carbon dioxide reduction to carbon monoxide (3), in demonstrations of efficient solar-to-fuels conversion. Recently, oxide-derived copper emerged as an intriguing electrocatalyst for the conversion of carbon dioxide into hydrocarbon products. In an effort to modify the product selectivity of copper oxide nanowire arrays, we used atomic layer deposition to apply conformal layers of tin oxide to the electrode surface. This copper-tin-oxide hybrid exhibited nearly unity selectivity for carbon monoxide as CO2 reduction product, deviating significantly from the behavior expected for copper or tin alone, neither of which typically produce CO at high selectivity. This result suggests sub-monolayer composition modification of electrode surfaces can be a powerful strategy for tuning electrocatalyst selectivity. J. Luo, L. Steier, M.-K. Son, M. Schreier, M. T. Mayer and M. Grätzel, Nano Letters, 2016, 16, 1848–1857.P. Dias, M. Schreier, S. D. Tilley, J. Luo, J. Azevedo, L. Andrade, D. Bi, A. Hagfeldt, A. Mendes, M. Grätzel and M. T. Mayer, Adv. Energy Mater., 2015, 5, 1501537.M. Schreier, J. Luo, P. Gao, T. Moehl, M. T. Mayer and M. Grätzel, J. Am. Chem. Soc., 2016, 138, 1938–1946.M. Schreier, F. Héroguel, L. Steier, S. Ahmad, J. S. Luterbacher, M. T. Mayer, J. Luo and M. Grätzel, Nature Energy, 2017, 2, 17087.

One-step preparation of ultra-thin copper oxide nanowire arrays/copper wire electrode for non-enzymatic glucose sensor

A novel binder-free glucose sensor based on vertically aligned ultra-thin copper oxide nanowire arrays (CuO NWAs) grown on copper wire (CW) was developed by using a simple and fast heat treatment method. Scanning electron microscope and transmission electron microscopy results showed that the length and diameter of CuO NWAs were about 8 μm and 40 nm, respectively. The electrochemical performance of CuO NWAs/CW electrode for glucose oxidation was studied in alkaline solution by cyclic voltammetry and chronoamperometry. Results showed that the novel integrated electrode exhibited good electrocatalytic performance toward glucose oxidation with wide linear ranges of 5.0 μM to 0.555 mM and 0.555 to 8.555 mM, high sensitivity of 850.7 and 446.7 μA mM−1 cm−2, and detection limit of 2.86 μM (S/N = 3). The good sensing performance was attributed to the superior electrocatalysis activity of high-density CuO NWAs with large active surface area.

Effect of graphene oxide nanosheets on visible light-assisted antibacterial activity of vertically-aligned copper oxide nanowire arrays

In the present work, the effect of graphene oxide (GO) nanosheets on the antibacterial activity of CuO nanowire arrays under visible light irradiation is shown. A combined thermal oxidation/electrophoretic deposition technique was employed to prepare three-dimensional networks of graphene oxide nanosheets hybridized with vertically aligned CuO nanowires. With the help of standard antibacterial assays and X-ray photoelectron spectroscopy, it is shown that the light-activated antibacterial response of the hybrid material against gram-negative Escherichia coli is significantly improved as the oxide functional groups of the GO nanosheets are reduced. In order to explore the physicochemical mechanism behind this behavior, ab-initio simulations based on density functional theory were performed and the effect of surface functional groups and hybridization were elucidated. Supported by the experiments, a three-step photo-antibacterial based mechanism is suggested: (i) injection of an electron from CuO into rGO, (ii) localization of the excess electron on rGO functional groups, and (iii) release of reactive oxygen species lethal to bacteria. Activation of new photoactive and physical mechanisms in the hybrid system makes rGO-modified CuO nanowire coatings as promising nanostructure devices for antimicrobial applications in particular for dry environments.

Utilizing Waste Cable Wires for High‐Performance Fiber‐Based Hybrid Supercapacitors: An Effective Approach to Electronic‐Waste Management

AbstractIn recent years, electronic waste (e‐waste) such as old cable wires, fans, circuit boards, etc., can be often seen in large piles of leftover in dumping yards. Employing these e‐waste sources for energy storage devices not only increases the economic value but also decreases the reliance on fossil fuels. In this context, waste cable wires are utilized to obtain precious copper (Cu) fibers and used as a cost‐effective current collector for the fabrication of fiber‐based hybrid supercapacitor (FHSC). With the braided Cu fibers, forest‐like nickel oxide nanosheet grafted carbon nanotube coupled copper oxide nanowire arrays (NiO NSs@CNTs@CuO NWAs/Cu fibers) are designed via simple wet‐chemical approaches. As a battery‐type material, the forest‐like NiO NSs@CNTs@CuO NWAs/Cu fiber electrode shows superior electrochemical properties including high specific capacity (230.48 mA h g−1) and cycling stability (82.72%) in aqueous alkaline electrolyte. Moreover, a solid‐state FHSC is also fabricated using forest‐like NiO NSs@CNTs@CuO NWAs/Cu fibers as a positive electrode and activated carbon coated carbon fibers as a negative electrode with a gel electrolyte, which also shows a higher energy and power densities of 26.32 W h kg−1 and 1218.33 W kg−1, respectively. The flexible FHSC is further employed as an energy source for various electronic gadgets, demonstrating its suitability for wearable applications.

Three-Dimensional Copper Foam Supported CuO Nanowire Arrays: An Efficient Non-enzymatic Glucose Sensor

Metal and metal oxides with various nanostructures have been widely studied in non-enzymatic glucose sensing. In this work, we report an efficient catalyst platform, which is made of three-dimensional copper foam (CF) skeleton and copper oxide nanowire arrays (CuONWA), is used to construct glucose sensor. The three-dimensional CuONWA/CF was synthesized via a facile wet-chemical method and subsequent annealing. The CuONWA is evenly covered by CuO nanoflowers. The morphology and composition of the platform were characterized. The nanowire arrays and nanoflowers both enhanced the electrocatalytic performance of the integrated electrode via greatly increasing the surface area of the CF substrate. The electrocatalytic properties of the non-enzymatic glucose sensor were characterized by a series of electrochemical measurements. The sensor exhibits excellent performance, with a linear range of 0.10μM–0.50mM, a sensitivity of 32330μAmM−1cm−2, a low limit of detection of 20nM (S/N=3), excellent selectivity, reproducibility, and stability. The sensor was also used for glucose sensing in human serum and Wahaha ice black tea, with relative standard deviations (for n=6) of 3.15% and 2.43%, respectively.

Templated electrodeposition of vertically aligned copper oxide nanowire arrays on 3D Ni foam substrates for determination of glucosamine in pharmaceutical caplet samples

A copper oxide nanowire network electrode has been fabricated through an electrodeposition procedure using mesoporous silica film as the template on Ni foam.

Sculpturing metal foams toward bifunctional 3D copper oxide nanowire arrays for pseudo-capacitance and enzyme-free hydrogen peroxide detection

Nanoengineered copper foam with 3D free-standing CuO nanowires is used for enhanced pseudocapacitance energy storage and electroanalysis of H2O2.

Tungsten Oxide Coated Copper Oxide Nanowire Arrays for Enhanced Activity and Durability with Photo-Electro-Chemical Water Splitting

: Recently, we showed that the deposition of crystalline WO3 layers on copper oxide nanowire arrays to result in a five-fold improvement of photocurrent density (~ 1.7 mA/cm2 at 0 V 10 vs. RHE) over titania coated copper oxide NW arrays. Most importantly, the deposition of WO3 or CuWO4 reduced CuO phase impurity to Cu2O. Improvement in the phase purity of nanowire arrays, led to the enhancement in photoactivity.1 The origin of degradation in photoelectrochemical performance with time is currently being investigated. Introduction : Photoelectrochemical (PEC) water splitting using sunlight is an attractive approach for producing clean hydrogen towards reducing carbon dioxide emissions and meeting the growing global energy demand. The biggest obstacle with PEC water splitting is the unavailability of a suitable semiconductor with proper band gap and band edge energetics and durability. Cu2O is a promising semiconducting material for photo-electro-chemical water splitting due to its band gap (Eg = 2.0 eV) and its band edge 25 positions straddling the water oxidation and reduction reactions. Major drawbacks with Cu2O include its poor stability in aqueous solutions, short carrier diffusion lengths (20-100 nm) and high absorption depth (10 microns). A semiconductor with a 2 eV band gap is expected to yield a photocurrent density of about 15 mA/cm2. The photoactivity performance of Cu2O has been a major concern, in addition to its rapid dissolution in aqueous solution.One-dimensional nanostructures such as nanowires have the potential to produce high photoactivity due to fast charge transport properties and reduced length scales for minority carrier diffusion expected in single crystalline nanowires. In our previous work, we developed a rapid two-step process for the scalable synthesis of copper oxide nanowire arrays on copper foils.2 This involves a wet chemical oxidation of copper foils followed by oxidation in atmospheric microwave plasma. The nanowire arrays were subsequently coated with titania using atomic layer deposition to improve the aqueous stability. The photocurrents obtained with this method are much lower (<0.4 mA/cm2) but better than the data obtained with polycrystalline thin films to that date. The presence of a mixed phase of Cu2O and CuO has been identified as a possible cause for the low photoactivity. CuO has an indirect band gap of 1.4 eV leading to inefficient photon absorption and also cannot generate sufficient energy required to split water. Hence, phase purity of Cu2O is an important factor that needs to be addressed to improve the photoactivity of the Cu2O NW arrays made through atmospheric plasma oxidation. In this contribution, we investigated the use of n-type crystalline WO3 conformal layers on Cu2O nanowire arrays using hot wire chemical vapor deposition and studied their impact on photoactivity and durability. Experimental: Copper oxide nanowire arrays were synthesized by wet chemical oxidation followed by short exposure to atmospheric plasma. Copper foils were immersed in an aqueous solution of sodium hydroxide and ammonium persulfate. The copper hydroxide nanowires produced were converted into copper oxide nanowires by means of exposure to an atmospheric plasma discharge for 2 minutes. The details of the process are described elsewhere. The deposition of WO3 or CuWO4 was performed in a HWCVD reactor using oxygen flow over hot tungsten and copper filaments used as the sources for tungsten oxide and copper oxide vapors. Results and Discussion: The copper oxide nanowires are coated with titania layer using atomic layer deposition and tungsten oxide layers and copper tungstate layers using hot-wire chemical vapor deposition. The PEC characterization studies show 3-4 times enhancement in photoactivity for copper tungstate coated copper oxide nanowire arrays compared to that titania coated copper oxide nanowire arrays. See Figure 1. Acknowledgements: Financial support from US DOE (DE-FG02-07ER46375) is acknowledged.

Copper oxide nanowire arrays synthesized by in-situ thermal oxidation as an anode material for lithium-ion batteries

Copper oxide nanowires with an average length of 7.4μm are prepared by in-situ thermal oxidation at 500°C for 6h in air, and their lithium storage performances are promoted by a further ammonia treatment. The morphologies, structures and lithium storage properties of copper oxide nanowire arrays are investigated by X-ray diffraction, scanning electron microscopy, high-resolution transmission electron microscopy and a series of electrochemical measurements. The results show that after the reprocessing, the CuO nanowire arrays exhibit a higher reversible capacity of 645 mAhg−1 after 100 cycles at a current density of 50 mAg−1, excellent cyclability and high-rate capability. The good electrochemical performance and simple preparation process make it a promising anode material for lithium-ion batteries.

Tungsten oxide-coated copper oxide nanowire arrays for enhanced activity and durability with photoelectrochemical water splitting

The deposition of crystalline CuWO4 and WO3 layers on copper oxide nanowire arrays resulted in a five-fold improvement of the photocurrent density (∼1.7 mA cm−2 at −0.1 V vs. RHE) over titania-coated copper oxide NW arrays. The deposition of WO3 or CuWO4 reduced the CuO phase impurities in Cu2O. The improvement in the phase purity of the nanowire arrays led to a considerable enhancement in the resulting photoactivity. These protective coatings have been shown to play a dual role of marginally extending the durability of the electrode and promoting charge separation.

Scalable synthesis and photoelectrochemical properties of copper oxide nanowire arrays and films

Here, we present a scalable method based on both atmospheric plasma and wet chemical oxidation methods to synthesize thin films and nanowire arrays of both cupric and cuprous oxides. In terms of nanowire arrays, the wet chemical oxidation is shown to produce copper hydroxide nanowire arrays on copper foils using hydrogen peroxide as the oxidant similar to ammonium persulfate. Experiments using different concentrations of hydrogen peroxide at constant pH resulted in higher nucleation density and smaller diameter of copper hydroxide nanowires. A scheme involving a short period of wet oxidation followed by plasma annealing resulted in high number density of Cu2O nanowire arrays. The overall process is rapid on the order of 1min reaction time scale. Photoelectrochemical characterization of titania coated copper oxide nanowire and thin film electrodes showed that the nanowire array electrodes exhibited significantly higher photoactivity than the thin film electrodes. The performance of resulting Cu2O NW array electrodes can be optimized further with other protective coatings.