Cobalt Oxide-Decorated Silicon Carbide Nano-Tree Array Electrode for Micro-Supercapacitor Application

A cobalt oxide (Co3O4)-decorated silicon carbide (SiC) nano-tree array (denoted as Co3O4/SiC NTA) electrode is synthesized, and it is investigated for the use in the micro-supercapacitor. Firstly, the well-standing SiC nanowires (NWs) are prepared by nickel (Ni)-catalyzed chemical vapor deposition (CVD) method, and then the thin layer of Co3O4 and the hierarchical Co3O4 nano-flower-clusters are, respectively fabricated on the side-walls and the top side of the SiC NWs via electrodeposition. The deposition of Co3O4 on the SiC NWs benefits for the charge transfer at the electrode/aqueous electrolyte interface due to its extremely hydrophilic surface characteristic after Co3O4 decoration. Furthermore, the Co3O4/SiC NTA electrode would possess a directional charge transport route along the nanowire length of SiC NWs owing to their well-standing architecture. By using the Co3O4/SiC NTA electrode for micro-supercapacitor, the areal capacitance obtained from cyclic voltammetry measurement reaches 845 mF cm−2 at a 10 mV s−1 scan rate. Finally, the capacitance durability is also evaluated by the cycling test of cyclic voltammetry at a high scan rate of 150 mV s−1 for 2000 cycles.

Synthesize Fe2O3 Polyhedral Applying for Rechargeable Batteries

Polyhedral Fe2O3 materials were synthesized by hydrothermal method. Their structure, size, and morphology were investigated by X-ray diffraction and scanning electron microscopy. The electrochemical characteristics of Fe2O3 electrodes were studied via cyclic voltammetry measurement. The effects of the additives on the electrochemical properties of the electrode were also studied. The results show that the synthesized polyhedral Fe2O3 presented the clear redox peaks. Combined with electrode additive nanocarbon and electrolyte additive K2S, the Fe2O3/C composite electrodes gave higher redox current, larger redox peaks. This demonstrates the important role of additives such as nanocarbon increased the electrical conductivity and the active surface area of ​​the electrode, while K2S enhanced the redox reaction rate of iron, improved the cycleability of iron oxide, and thus increased the discharge capacity of Fe2O3/C electrodes. Polyhedral Fe2O3 synthesized via hydrothermal route has a potential applying as negative electrode in rechargeable batteries.

Electrochemical Impedance Spectroscopy Microsensor Based on Molecularly Imprinted Chitosan Film Grafted on a 4-Aminophenylacetic Acid (CMA) Modified Gold Electrode, for the Sensitive Detection of Glyphosate

A novel electrochemical impedance spectroscopy (EIS) microsensor was implemented for the dosage of traces of glyphosate, in real and synthetic water samples. Molecularly imprinted chitosan was covalently immobilized on the surface of the microelectrode previously modified with 4-aminophenylacetic acid (CMA). The characterization of the resulting microelectrodes was carried out by using cyclic voltammetry measurement (CV), scanning electron microscopy (SEM), and electrochemical impedance spectrometry (EIS). EIS responses of the CS-MIPs/CMA/Au microsensor toward GLY was well-proportional to the concentration in the range from 0.31 × 10−9 to 50 × 10−6 mg/mL indicating a good correlation. The detection limit of GLY was 1 fg/mL (S/N = 3). Moreover, this microsensor showed good reproducibility and repeatability, high selectivity, and can be used for the detection of GLY in river water.

Performance Characteristics of Lithium Titanate Doped Zirconium as Anode Material of Lithium Ion Battery and Its Potential for Cycle Recovery

Lithium titanate or (Li4Ti5O12) is one of potential materials applied as anode material for energy storage device. The material, however, has poor electrochemical properties. This study is aimed to study Zr-doped Li4Ti5O12 properties and electrochemical performance in a full cell. In this work, a facile solid state reaction is employed to prepare Li4Ti5-xO12Zrx (x=0, 0.025, 0.05, and 0.075). Starting materials were stoichiometrically calculated and handily mixed for an hour, followed by calcination at 800oC for three hours. The XRD pattern reveals that the shipments to the higher angel of the highest peak are observed and indicate successful substitution process. The half-cell (Li metal/Li4Ti4.95O12Zr0.05) provides the highest conductivity value of the assembled cells, 0.15 mS cm-1. Cyclic Voltammetry measurement exhibits that the reduction peak of each half-cell is enhanced as an increasing amount of zirconium. The Charge-Discharge test also confirm that the highest capacity of the cells, 135.0 mAhg-1, is achieved by the cell based Li4Ti4.95O12Zr0.05. Full cell performance present that Li4Ti4.95O12Zr0.05 own higher capacity at various C-rates. Moreover, the specific capacitance of full cell based Li4Ti4.95O12Zr0.05 can sustain 82% after 100th cycle at 0.5C, higher than that of Li4Ti5O12 (22.4%). In addition, full cell performance also exhibits a potential for recovery cycle as shown in 90th cycle.

Electrocatalytic Oxidation of Glucose on Boron and Nitrogen Codoped Graphene Quantum Dot Electrodes in Alkali Media

A novel solvothermal technique has been developed in the presence of C/N/B precursor for synthesizing B-N-coped graphene quantum dots (GQDs) as non-metal electrocatalysts towards the catalytic glucose oxidation reaction (GOR). Both N-doped GQD and B-N-codoped GQD particles (~4.0 nm) possess a similar oxidation and amidation level. The B-N-codoped GQD contains a B/C ratio of 3.16 at.%, where the B dopants were formed through different bonding types (i.e., N‒B, C‒B, BC2O, and BCO2) inserted into or decorated on the GQDs. The cyclic voltammetry measurement revealed that the catalytic activity of B-N-codoped GQD catalyst is significantly higher compared to the N-doped GQDs (~20% increase). It was also shown that the GOR activity was substantially enhanced due to the synergistic effect of B and N dopants within the GQD catalysts. Based on the analysis of Tafel plots, the B-N-codoped-GQD catalyst electrode displays an ultra-high exchange current density along with a reduced Tafel slope. The application of B-N-codoped GQD electrodes significantly enhances the catalytic activity and results in facile reaction kinetics towards the glucose oxidation reaction. Accordingly, the novel design of GQD catalyst demonstrated in this work sets the stage for designing inexpensive GQD-based catalysts as an alternative for precious metal catalysts commonly used in bio-sensors, fuel cells, and other electrochemical devices.

Organic electrochemical transistor arrays for real-time mapping of evoked neurotransmitter release in vivo

Though neurotransmitters are essential elements in neuronal signal transduction, techniques for in vivo analysis are still limited. Here, we describe an organic electrochemical transistor array (OECT-array) technique for monitoring catecholamine neurotransmitters (CA-NTs) in rat brains. The OECT-array is an active sensor with intrinsic amplification capability, allowing real-time and direct readout of transient CA-NT release with a sensitivity of nanomolar range and a temporal resolution of several milliseconds. The device has a working voltage lower than half of that typically used in a prevalent cyclic voltammetry measurement, and operates continuously in vivo for hours without significant signal drift, which is inaccessible for existing methods. With the OECT-array, we demonstrate simultaneous mapping of evoked dopamine release at multiple striatal brain regions in different physiological scenarios, and reveal a complex cross-talk between the mesolimbic and the nigrostriatal pathways, which is heterogeneously affected by the reciprocal innervation between ventral tegmental area and substantia nigra pars compacta.

Structure and Electrochemical Properties of Li4Ti5O12 Prepared via Low-Temperature Precipitation

This work aimed to prepare the spinel phase Li4Ti5O12 by a combination of the low-temperature precipitation technique and assisted calcination step. X-ray diffraction (XRD) revealed that the intermediated phase was Li2TiO3, and the spinel phase could be evidently formed at 700°C for 12 to 20 hours. The morphology of spinel powder, determined by SEM and TEM, exhibited a good distribution at the submicrometric scale that promoted a fast kinetic of Li migration and an excellent performance at the high-rate cycling test. The stable performances were achieved in the charge-discharge test at different current densities: 80 mA/g (165 mAh/g), 320 mA (160 mAh/g), and 1600 mA (145 mAh/g) upon 100 cycles. Moreover, we observe a capacity retention of 48% (corresponding 80 mA/g) at a high rate of 5000 mAh/g. The cyclic voltammetry measurement displayed a reversible system and revealed the lithium diffusion coefficient of 1.15 × 10−11 cm2/s.

Solid State Gas Sensor Based on Polyaniline Doped with [3,3′-Co(1,2-C2B9H11)2]−1 for Detection of Acetone: Diagnostic to Heart Failure Disease

Acetone in human breath has been regarded as the important disease marker of Heart failure (HF). Therefore, preliminary study has been carried out for the use chemical sensor based on Polyaniline doped with [3,3′-Co(1,2-C2B9H11)2]−1 anion (PANI/COSANE) for the detection and quantification of acetone in human breath. This chemical sensor was prepared by Galvano-statically growing a polymeric layer based on PANI/COSANE and PANI/Nitrate by electrochemical polymerization onto the two different interdigitated gold microelectrodes on a silicon chip surface using cyclic voltammetry. Measurement of change in conductance due to the presence of acetone in its vicinity at room temperature (20–25 °C) is performed in differential configuration mode using Lock-in amplifier. The developed acetone sensor has been calibrated under different acetone atmospheres using a Lock-in amplifier. This novel Acetone micro sensor showed good response, recovery, and stability for the detection of acetone in the range of 1 ppm–8 ppm.

Spray Pyrolysis Technique for the deposition of Lead Oxide (PbO) Thin Films; its Electrochemical behaviour and Structural and optical Properties

Thin film of Lead oxide (PbO) was prepared by spray pyrolysis technique on glass substrate at 250°C. The cyclic voltammetry measurement was carried out to study the oxidation reduction reactions of non-aqueous lead ions at various molar concentrations which is from 0.01M to 0.09M. Elecrochemical studies were carried out with Ag/AgCl as a reference electrode , Pt as working electrode while platinum mesh as counter electrode.Lead oxide appears to be poisonous yellow or reddish yellow solid. Structural characterization of films was analyze with X- ray diffraction (XRD) and optical band gap was determined by UV-Vis Spectroscopy.

Preparation of NiPt Alloys by Galvanic Replacement Reaction on Ni Films for Direct Ethanol Fuel Cell

NiPt alloys were prepared successfully by galvanic replacement reaction on the surface of Ni films. The electrolytic deposition of Ni films was investigated to get the high qualities of Ni films for the galvanic reaction. The influence of the electrolytic currents on the morphology and thickness of Ni films were observed by SEM. The thickness and roughness of the Ni films increase with the increase of electrolytic currents. XRD patterns showed that Ni films were formed in the crystal phase of Ni corresponding to face centered cubic structure. Pure Ni films obtained by annealing the films in hydrogen medium were used to prepare NiPt alloys due to galvanic reaction of Pt2+ with Ni2+ in H2PtCl6 solution. The influence of the H2PtCl6 solution concentration on the composition of NiPt alloys were investigated by EDX. The analyses results showed that NiPt alloy formed by using high solution concentration of H2PtCl6 has high composition of Pt. The electrocatalytic activities of both Ni films and NiPt alloys toward ethanol oxidation in KOH medium were carried out by the cyclic voltammetry measurement. Alloyed samples exhibited high electrocatalytic activities due to carbonaceous removal and weakening Pt-COads bond.