Oxide Nanocomposite Electrode Research Articles

Development of Graphenated Polyamic Acid Sensors for Electroanalytical Detection of Anthracene

Polyaromatic hydrocarbons (PAHs) are typically present in environmental samples at very low concentrations. Therefore, extensive sample preparation is necessary to enhance the signal for analytical determination of these compounds by classical methods based on chromatography or spectroscopy. In this study an electrochemical sensor for anthracene based on polyamic acid- graphene oxide (PAA-GO) nanocomposite electrode was prepared for application in the direct analysis of small volumes of samples with minimal pre-treatment steps. Polyamic acid and graphene oxide (GO) are materials with well-defined electrochemistry of their own and both are readily synthesised under ambient laboratory conditions. The sensor was prepared by cyclic voltammetric co-deposition of PAA and GO onto a commercial screen printed carbon electrode (SPCE) in five voltammetric cycles with initial and switch potentials of -1000 mV and +1000 mV, respectively, at a potential scan rate of 50 mV/s. The sensor materials (GO, PAA and PAA-GO) were characterised by Fourier transform infrared spectroscopy (FTIR), high resolution scanning electron microscopy (HRSEM) and cyclic voltammetry (CV), while their corresponding screen printed electrode systems (GO/SPCE, PAA/SPCE and PAA-GO/SPCE) were evaluated as possible chemical sensors for anthracene.

Binder‐Free Carbon‐Coated Silicon–Reduced Graphene Oxide Nanocomposite Electrode Prepared by Electrophoretic Deposition as a High‐Performance Anode for Lithium‐Ion Batteries

AbstractA simple yet versatile binder‐free electrophoretic deposition method is developed to fabricate a carbon‐coated Si/reduced graphene oxide (Si@C/rGO) nanocomposite as a high‐performance anode for lithium‐ion batteries. In this nanostructure, high specific capacity Si nanoparticles are uniformly coated with the carbon layer and embedded in graphene sheets to form an integrated, robust and conductive framework. Electrochemical studies show that this nanostructured Si@C/rGO electrode exhibits a high reversible specific capability (1165 mA h g−1 at 0.1 A g−1, three times of that of graphite) and excellent cycling stability (capacity retention of 96.8 % at 1 A g−1, and 95.4 % at 2 A g−1 after 100 cycles).

Facile Synthesis of Pt-CuO Nanocomposite Films for Non-Enzymatic Glucose Sensor Application

Nanocomposite films of Pt-CuO were synthesized via galvanostatic electrodeposition combined with galvanic replacement and post-synthesis thermal anneal. First, Cu-Cu2O composite was prepared by galvanostatic electrodeposition; heat-treatment of the as-prepared Cu-Cu2O composite at 375°C for 10 h resulted in a CuO electrode showing response to glucose with long term stability. Further enhanced response to glucose was obtained with a Pt-CuO electrode, which was synthesized by galvanic replacement of Cu-Cu2O in 10 mM PtCl4 solution for 30 s followed by annealing at 375°C for 10 h. The resulting Pt-CuO electrode showed excellent response to glucose in alkaline solution with an analytical sensitivity of 3812 μAmM−1cm−2, a limit of detection (LOD) of 7.5 μM, and a linear response range to glucose up to 0.6 mM. These results may be extended to the fabrication of other noble metal-metal oxide nanocomposite electrodes for sensor applications.

Implantable Graphene-based Neural Electrode Interfaces for Electrophysiology and Neurochemistry in In Vivo Hyperacute Stroke Model

Implantable microelectrode arrays have attracted considerable interest due to their high temporal and spatial resolution recording of neuronal activity in tissues. We herein presented an implantable multichannel neural probe with multiple real-time monitoring of neural-chemical and neural-electrical signals by a nonenzymatic neural-chemical interface, which was designed by creating the newly developed reduced graphene oxide-gold oxide (rGO/Au2O3) nanocomposite electrode. The modified electrode on the neural probe was prepared by a facile one-step cyclic voltammetry (CV) electrochemical method with simultaneous occurrence of gold oxidation and GOs reduction to induce the intimate attachment by electrostatic interaction using chloride ions (Cl(-)). The rGO/Au2O3-modified electrode at a low deposition scan rate of 10 mVs(-1) displayed significantly improved electrocatalytic activity due to large active areas and well-dispersive attached rGO sheets. The in vitro amperometric response to H2O2 demonstrated a fast response of less than 5 s and a very low detection limit of 0.63 μM. In in vivo hyperacute stroke model, the concentration of H2O2 was measured as 100.48 ± 4.52 μM for rGO/Au2O3 electrode within 1 h photothrombotic stroke, which was much higher than that (71.92 μM ± 2.52 μM) for noncoated electrode via in vitro calibration. Simultaneously, the somatosensory-evoked potentials (SSEPs) test provided reliable and precise validation for detecting functional changes of neuronal activities. This newly developed implantable probe with localized rGO/Au2O3 nanocomposite electrode can serve as a rapid and reliable sensing platform for practical H2O2 detection in the brain or for other neural-chemical molecules in vivo.

A sol–gel derived, copper-doped, titanium dioxide–reduced graphene oxide nanocomposite electrode for the photoelectrocatalytic reduction of CO2to methanol and formic acid

Highly efficient photoelectrocatalytic reduction of CO2into methanol and formic acid at Cu doped RGO–TiO2photoelectrode.

Sensitive Detection of Hydroxylamine on Poly(3,4- ethylenedioxythiophene)/graphene Oxide Nanocomposite Electrode

Sensitive Detection of Hydroxylamine on Poly(3,4- ethylenedioxythiophene)/graphene Oxide Nanocomposite Electrode

Ecofriendly Approach to Making Graphene–Tin/Tin Oxide Nanocomposite Electrodes for Energy Storage

AbstractA sustainable, nontoxic, and ecofriendly lithium‐ion battery is the ultimate dream in the field of energy storage. First, the ecofriendly production of large quantities of electrode material is a great challenge. Herein, a green process for making tin‐/tin oxide‐based alloy electrodes by means of a simple solvent [N,N‐dimethylformamide (DMF)]‐assisted self‐reduction method is proposed. The end products of this reduction process are identified as dimethylamine (DMA), carbon dioxide, and hydrochloric acid. Both the solvent (DMF) and reaction product (DMA) are biodegradable and the reaction byproducts (DMA and CO2) can be reconverted back into DMF. The simple mixing of two colloids in the same solvent (DMF) is adopted to incorporate tin nanoparticles into a graphene matrix; this helps to distribute nanoparticles on the graphene surfaces. The resulting nanocomposite displays an improved reversible capacity of 750 mAh g−1 at a current rate of 160 mA g−1, with stable cyclic retention and a discharge capacity of more than 600 mAh g−1 at a high current rate of 700 mA g−1 after 35 cycles. The effect of graphene on nanoparticle shape management during electrochemical cycling is studied by using transmission electron microscopy.

Preparation of polyaniline/graphene oxide nanocomposite for the application of supercapacitor

Abstract Graphene oxide was synthesized by an improved Hummers method. Three polyaniline (PANI)/graphene oxide (GO) nanocomposite electrode materials were prepared from aniline (ANI), GO, and ammonium persulfate (APS) by chemical polymerization with the mass ratio ( m ANI : m GO ) 1000:1, 100:1, and 10:1 in ice water, respectively. The crystal structure and the surface topography of all materials were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectrum (FT-IR) and scanning electron microscopy (SEM). The electrochemical properties of the composite were evaluated by cyclic voltammetry, galvanostatic charge/discharge, and the impedance spectroscope, respectively. The test results show that the composites have similar and enhanced cyclic voltammetry performance compared with pure PANI based electrode material. The PANI/GO composite synthesized with the mass ratio ( m ANI : m GO ) 1000:1 possessed excellent capacitive behavior with a specific capacitance as high as 355.2 F g −1 at 0.5 A g −1 in 1 mol L −1 H 2 SO 4 electrolyte due to the unique morphology of Mace-like PANI/GO composite, and after 1000 cycles, the specific capacitance of the composite still has 285.8 F g −1 . These results demonstrate exciting potentials of the composite for high performance supercapacitors or other power source system.

Nanostructured CuO/reduced graphene oxide composite for hybrid supercapacitors

To address the issues such as low ionic conductivity, poor electrode kinetics and cyclic stability, the strategy of combining carbon-based materials with transition metal oxide (TMO) is adopted. In this article, the preparation of CuO/reduced graphene oxide (RGO) nanocomposite electrodes by a simple, low cost hydrothermal method is described. This hybrid nanocomposite exhibits a high specific capacitance of 326 F g−1 at a current density of 0.5 A g−1. It shows a high energy density of 65.7 W h kg−1 at a power density of 302 W kg−1. Further, this material does not exhibit any measureable degradation in electrochemical performance, even after 1500 cycles. Symmetric hybrid capacitors exhibit a specific capacitance of 97 F g−1 at 0.2 A g−1 with a power density of 72 W kg−1. These superior electrochemical features demonstrate that the CuO/RGO hybrid nanocomposite is a promising material for next-generation supercapacitor systems.

Nickel-cobalt nanostructures coated reduced graphene oxide nanocomposite electrode for nonenzymatic glucose biosensing

Nickel-cobalt nanostructures (Ni-Co NSs) electrodeposited on reduced graphene oxide (RGO)-modified glassy carbon electrode (GCE) was prepared and used for highly sensitive glucose detection. RGO nanosheets were firstly assembled onto GCE surface by π–π interaction and then Ni-Co NSs were constructed on RGO/GCE by dynamic potential scan. The electrochemical and electrocatalytic behaviors of the Ni-Co NSs/RGO/GCE toward glucose oxidation were evaluated by cyclic voltammograms, chronoamperometry and amperometric method. The effects of some factors related to the fabrication of Ni-Co NSs/RGO/GCE, such as potential scan number and the molar ratio of Ni2+/Co2+ in a solution, on the catalytic performance of the Ni-Co NSs/RGO/GCE were also explored. The results showed that the Ni-Co NSs/RGO/GCE exhibited the best catalytic activity at the potential scan number of 20 and the Ni2+/Co2+ molar ratio of 1:1. The glucose concentration in the range of 10μM to 2.65mM linearly depended on the catalytic current (r=0.9967, n=17). The sensitivity was 1773.61μAcm−2mM−1, and the detection limit was 3.79μM (S/N=3). This high catalytic activity, good sensitivity and stability of the Ni-Co NSs/RGO/GCE sensor opened up a new kind of hybrid materials in electrochemical detection of glucose.

SnO2/Reduced Graphene Oxide Nanocomposite for the Simultaneous Electrochemical Detection of Cadmium(II), Lead(II), Copper(II), and Mercury(II): An Interesting Favorable Mutual Interference

A well-known gas sensing material SnO2 in combination with reduced graphene oxide was used in heavy metal ions detection for the first time. This work reports the detailed study on the SnO2/reduced graphene oxide nanocomposite modified glass carbon electrode, which could be used for the simultaneous and selective electrochemical detection of ultratrace Cd(II), Pb(II), Cu(II), and Hg(II) in drinking water. The SnO2/reduced graphene oxide nanocomposite electrode was characterized voltammetrically using redox couples (Fe(CN)63–/4–), complemented with electrochemical impedance spectroscopy (EIS). Square wave anodic stripping voltammetry (SWASV) has been used for the detection of Cd(II), Pb(II), Cu(II), and Hg(II). The detection limit (3σ method) of the SnO2/reduced graphene oxide nanocomposite modified GCE toward Cd(II), Pb(II), Cu(II) and Hg(II) is 1.015 × 10–10 M, 1.839 × 10–10 M, 2.269 × 10–10 M, and 2.789 × 10–10 M, respectively, which is very well below the guideline value given by the World Health Organ...

Synthesis of cuprous oxide nanocomposite electrodes by room-temperature chemical partial reduction

We demonstrate a template-free synthetic approach for the preparation of a highly conductive Cu/Cu(2)O nanocomposite electrode by a chemical reduction process. Cu(2)O octahedra were prepared through chemical dehydrogenation of as-synthesized Cu(OH)(2) nanowire precursors. To provide a sufficiently electron-conducting network, the Cu(2)O particles were transformed into Cu/Cu(2)O nanocomposites by an intentional reduction process. The Cu/Cu(2)O nanocomposite electrodes showed enhanced cycling performance compared to Cu(2)O particles. Furthermore, their rate capabilities were superior to those of their mechanically mixed Cu/Cu(2)O counterparts. This enhanced electrochemical performance of the hybrid Cu/Cu(2)O nanocomposites was ascribed to the formation of homogeneous nanostructures, offering an efficient electron-transport path provided by the presence of highly dispersed Cu nanoparticles.

Carbon Nanotube/Manganese Oxide Ultrathin Film Electrodes for Electrochemical Capacitors

Multiwall carbon nanotube (MWNT)/manganese oxide (MnO2) nanocomposite ultrathin film electrodes have been created via redox deposition of MnO2 on layer-by-layer (LbL)-assembled MWNT films. We demonstrate that these LbL-assembled MWNT (LbL-MWNT)/MnO2 thin films consist of a uniform coating of nanosized MnO2 on the MWNT network structure using SEM and TEM, which is a promising structure for electrochemical capacitor applications. LbL-MWNT/MnO2 electrodes yield a significantly higher volumetric capacitance of 246 F/cm3 with good capacity retention up to 1000 mV/s due to rapid transport of electrons and ions within the electrodes. The electrodes are generated with two simple aqueous deposition processes: the layer-by-layer assembly of MWNTs followed by redox deposition of MnO2 at ambient conditions, thus providing a straightforward approach to the fabrication of high-power and -energy electrochemical capacitors with precise control of electrode thickness at nanometer scales.

Nanocomposite electrode materials for high energy density rechargeable lithium batteries

The manganese and chromium oxide nanocomposite electrode materials were synthesized by redox reactions using transition metal powders in solutions. The layered Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)] O2 (x= 0.054, 0.0142, 0.147 and 0.311) materials having α-NaFeO2 (R-3 m) structure were prepared by solid-state reactions with LiOH and the pre-prepared manganese and chromium precursors. The amount of chromium, after removing the traces of Li2CrO4 from the prepared samples, is found to increase with temperature. The Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)] O2 material with x = 0.147 exhibits a high discharge capacity of 280 mAh g− 1 in the first cycle and a good reversible capacity of about 250 mAh g− 1 when cycled in the voltage range 2.0–4.9 V. Whereas, the Li[CrxLi(1/3 − x/3)Mn(2/3 − 2x/3)]O2 material with x = 0.311 delivers a very low initial discharge capacity of 98 mAh g−1, which is found to be increased up to a discharge capacity of about 260 mAh g− 1 at the 30th cycling. This drastic increase in capacity is attributed to the redox couples of Cr+ 4/Cr+ 6 and Cr+3/Cr+4.

A Hybrid Metal Oxide Supercapacitor in Aqueous KOH Electrolyte†

AbstractA novel type of composite electrode based on sheet like cobalt oxide particles has been used in supercapacitors. Cobalt oxide cathodically deposited from Co(NO3)2 solution with carbon nanotubes as matrix exhibited large pseudo‐capacitance of 322 F·g−1 in 6 mol·L−1 KOH. A sol‐gel process for the preparation of ultrafine RuO2 particles was developed to design electrodes with large surface area. The composite electrodes were developed by the deposition of RuO2 on the surface of carbon nanotubes. A specific capacitance of 785 F·g−1 can be achieved with the 20% carbon nanotubes loaded. To characterize the metal oxide nanocomposite electrode, a cyclic voltammetry and AC impedance test are executed. This study also reports a hybrid capacitor, which consists of cobalt oxide composite as a cathode and ruthenium oxide composite as an anode. The electrochemical performance of the hybrid capacitor is characterized by a dc charge/discharge test and cyclic voltammograms. The hybrid capacitor shows capacitor behavior with an extended operating voltage of 1.4 V. The maximum energy density and specific power density of the cell reach the value of 23.7 and 8.1 kW·g−1 respectively. The hybrid capacitor exhibits high‐energy density and stable power characteristics.