NiII1,4,8,11-tetraazacyclotetradecane electrocatalytic films prepared on top of surface anchored PAMAM dendrimer layers. A new type of electrocatalytic material for the electrochemical oxidation of methanol

Gold electrodes, previously prepared with surface anchored PAMAM dendrimers, were further modified with a Ni-containing tetraazamacrocycle resulting in a novel electrocatalytic material which proved to be particularly efficient for the electrochemical oxidation of methanol in basic aqueous medium.     

Mesoporous Co3O4 monolayer hollow-sphere array as electrochemical pseudocapacitor material

A Co(3)O(4) monolayer hollow-sphere array with mesoporous walls exhibits high pseudocapacitances of 358 F g(-1) at 2 A g(-1) and 305 F g(-1) at 40 A g(-1), as well as excellent cycling stability for application as pseudocapacitors.     

NdFeO3纳米晶的合成及气敏性能

以Nd2O3,Fe(NO3)3·9H2O,硝酸(1∶1)为原料,在柠檬酸体系中用溶胶凝胶法合成了具有钙钛矿结构的稀土复合氧化物NdFeO3;用XRD和TEM对产物的组成、颗粒大小、形貌进行了表征;结果表明:产物为纳米颗粒,平均粒径为28nm左右,且颗粒均匀。还采用静态配气法测试了材料的气敏性能,发现NdFeO3对H2S有很高的灵敏度,且抗干扰能力强,有较好的工业应用前景。     

Synthesis and electrochemical properties of Zn3V3O8 as novel anode material

Zn₃V₃O₈ two-dimensional micro sheets are successfully synthesized by combination of solvothermal method and heat treatment. The Zn₃V₃O₈ has better electrochemical performances after calcinations.     

Persulfate treatment as a method of modifying carbon electrode material for aqueous electrochemical capacitors

The activated carbon was modified by the wet method with a solution of ammonium persulfate at room temperature with different times. Kinetics studies showed that the modification took place mostly during the first 60 min of the process. The physicochemical properties of the obtained carbon were evaluated by thermogravimetric studies, Raman and FTIR spectroscopy, elementary and BET analyses. Furthermore, the fabricated material was applied in symmetric capacitors operated on the three aqueous electrolytes (1 M H₂SO₄, 6 M KOH and 1 M Na₂SO₄). Mild conditions of the modification process are optimal to obtain electroactive groups on the carbon surface, which make this material useful in a supercapacitor application. In our studies, we noticed that this type of functional groups mainly appears on the surface of the activated carbon, in the first oxidation stage. With prolonged oxidation, they may transform into undesirable groups. The results show that this kind of modification improves the capacity of all the tested supercapacitors. It was connected mainly with an increase of the carbon material’s wettability and in the case of capacitor operated in acid and base electrolytes due to a redox reaction of oxygen functional groups.

Open image in new window

Graphical abstract Persulfate treatment of carbon material.

     

Phenylboronic acid and dopamine as probe set for electrochemical detection of saccharides

A novel electrochemical approach for detection of saccharides via indicator displacement assay was presented. In this system, 2-fluorophenylboronic acid and dopamine (DA) were performed as probe set. The electrochemical properties of DA and the binding to 2-fluorophenylboronic acid in phosphate buffer at different pH values were investigated by cyclic voltammetry. After addition of fructose to the solution, a competition for the binding 2-fluorophenylboronic acid occurred that led to the release of the DA. The regenerate oxidation current of DA increased with increasing fructose concentration. Under optimized experimental conditions, the peak current was linearly related to fructose concentration in the range of 0.3-5.0 mmol/L with a detection limit of 0.1 mmol/L. In addition, the interaction between 2-fluorophenylboronic acid and other cis-diol compounds such as glucose, galactose and mannose was investigated.     

New electrode material GCE/AgNPs-D3 as an electrochemical sensor used for the detection of thallium ions

Optimal working parameters for the innovative electrode GCE/AgNPs-D3 were determined and the selectivity was assessed. The stripping anodic peak current of thallium characterized in linearity over range from 4.9 ⋅ 10⁻⁸ to 4.9 ⋅ 10⁻⁷ mol ⋅ dm⁻³, with LOD = 7.16 ppb (3.5 ⋅ 10⁻⁸ mol ⋅ dm⁻³). Furthermore, the new electrode showed more than sevenfold improvement in the thallium current signal compared to the unmodified electrode GCE. High selectivity was achieved using EDTA disodium salt as a complexing agent for other metals.     

Pyridinium bromide as a new mediator for electrochemical transformations involving CH-acids

1. Download : Download high-res image (70KB)
2. Download : Download full-size image

     

Investigating metal-organic framework as a new pseudo-capacitive material for supercapacitors

A new application of metal organic framework （MOF） as a pseudo-capacitive material for supercapacitors is investigated. To this end, a simple nickel-based MOF, formulated Ni3（btc）2.12H2O, is synthesized via a hydrothermal reaction. As an electro-active material, such nickel-based MOF exhibits superior pseudo- capacitive behavior in KOH aqueous electrolyte with a high specific capacitance of 726 F g-1. Also, it displays good electrochemical stability with 94.6% of the initial capacitance over consecutive 1000 cycles. In addition, a simple asymmetric supercapacitor with a high energy density of 16.5 Wh kg-1 is successfully built using the nickel-based MOF as positive electrode and commercial activated carbon as negative electrode in KOH electrolyte.     

Fe2O3 xerogel used as the anode material for lithium ion batteries with excellent electrochemical performance

A new strategy was applied to synthesise a porous nanostructure of α-Fe(2)O(3) xerogel assembled from nanocrystalline particles (～5 nm) with abundant mesopores (～3 nm) using a hydrothermal method. The α-Fe(2)O(3) xerogel exhibits excellent cycling performance (up to 1000 cycles) and rate capability (reversible discharging capacity 280 mAh g(-1) at 10 C) as a potential anode for high power lithium-ion batteries.     

Ionic liquid-functionalized graphene as modifier for electrochemical and electrocatalytic improvement: comparison of different carbon electrodes

Electrochemical activities of typically electrochemical targets at three kinds of modified carbon electrodes, i.e. carbon ionic liquid electrode (CILE), graphene/carbon paste electrode (CPE), and ionic liquid-functionalized graphene (IL-graphene)/CPE, were compared in detail. The redox processes of the probes at IL-graphene/CPE were faster than those at CILE and graphene/CPE from cyclic voltammetry. An electrochemical method for the simultaneous determination of guanine and adenine was described with detection limits of 6.5 × 10⁻⁸ mol L⁻¹ (guanine) and 3.2 × 10⁻⁸ mol L⁻¹ (adenine). Single A → G mutation of sequence-specific DNA could be discriminated by the IL-graphene/CPE.     

The electrochemical performance of AB3-type hydrogen storage alloy as anode material for the nickel metal hydride accumulators

For the purpose of lowering the cost of metal hydride electrode, the La of LaY₂Ni₉ electrode was replaced by Ce. The electrochemical performances of the CeY₂Ni₉ negative electrode, at a room and different temperatures, were compared with the parent alloy LaY₂Ni₉. At room temperature during a long cycling, the evolution of the electrochemical capacity—the diffusivity indicator (\( \frac{D_{\mathrm{H}}}{a^2} \))—the exchange current density, and the equilibrium potential were determined. At different temperatures, the electrochemical characterization of this alloy allowed the estimation of the enthalpy, the entropy, and the activation energy of the hydride formation. The evolution of the high-rate dischargeability was also evaluated at different temperatures. Compared with the parent LaY₂Ni₉ alloy, CeY₂Ni₉ exhibits an easy activation and good reaction reversibility. This alloy also conserves a good lifetime during a long-term cycling. A lower activation energy determined for this alloy corresponds to an easy absorption of hydrogen into this new alloy.     

Electrochemical characterization of MnO2 as electrocatalytic energy material for fuel cell electrode

 Development of inexpensive non Pt based high electrocatalytic energy materials is the need of the hour for fuel cell electrode to produce clean alternative green energy from synthesized bio alcohol using biomass. MnO₂, electro synthesized at different current density is found to be well performed electrocatalytic material, comparable to Pt, with higher current density, very low overvoltage for the electrochemical oxidation of methanol. From EIS study, the polarization resistance of the coated MnO₂ is found to be much low and electrical double layer capacitance is high, the effect increases with increase in current density of electro deposition. XRD, EDX and AAS analysis confirm the MnO₂ deposition. The morphology of SEM images exhibits an enhanced 3D effective substrate area, for electro oxidation of the fuel. A few nano structured grains of the deposited MnO₂ is also observed at higher current density. The fact supports that a high energetic inexpensive electro catalytic material has been found for fuel cell electrode to synthesis renewable energy from methanol fuel.     

Conductive polymers as a new type of thermoelectric material

Thermoelectric properties were investigated for the films of electrically conductive doped polyanilines. The thermoelectric performance, evaluated by thermoelectric figure-of-merit (ZT = T (S² σ) / κ), of various protonic acid-doped polyaniline bulk films was found to depend on the electrical conductivity σ of the film. Thus, the higher the electrical conductivity, the higher the figure-of-merit is, because the thermal conductivity κ of polyaniline films does not depend on the electrical conductivity. Among the conductive bulk films of polyaniline, the highest figure-of-merit (ZT = 1 × 10⁻⁴) was observed for (±)-10-camphorsulfonic acid (CSA)-doped polyaniline in an emeraldine form (σ - 188 S cm⁻¹) at room temperature. The multilayered film, composed of electrically insulating emeraldine base layers and electrically conducting CSA-doped emeraldine salt layers, exhibited 6 times higher ZT at 300 K than that of a bulk film of CAS-doped polyaniline, showing the highest ZT value of 1.1 × 10⁻² at 423 K. Stretching of the CAS-doped polyaniline film also increased the figure-of-merit of doped polyaniline films along the direction of the stretching.     

Partially reduced graphite oxide as an electrode material for electrochemical double-layer capacitors

Partially reduced graphite oxide was prepared from graphite oxide by using synthetic graphite as precursor. The reduction of graphite oxide with a layer distance of 0.57?nm resulted in a reduction of the layer distance depending on the degree of reduction. Simultaneously the amount of oxygen functionalities in the graphite oxide was reduced, which was corroborated by elemental analysis and EDX. The electrochemical activation of the partially reduced graphite oxide was investigated for tetraethylammonium tetrafluoroborate in acetonitrile and in propylene carbonate. The activation potential depends significantly on the degree of reduction, that is, on the graphene-layer distance and on the solvent used. The activation potential decreased with increasing layer distance for both positive and negative activation. The resulting capacitance after activation was found to be affected by the layer distance, the oxygen functionalities and the used electrolyte. For a layer distance of 0.43?nm and with acetonitrile as the solvent, a differential capacitance of 220?Fg(-1) was achieved for the discharge of the positive electrode near the open-circuit potential and 195?Fg(-1) in a symmetric full-cell assembly.     

A pH-controllable electrochemical molecule switch employing a new electrochemical measurement system as switching transducer

A new design concept of electrochemical pH-controllable molecular switch is presented by utilizing a new electrochemical measurement system as switching transducer. A pH sensor is connected in series between the terminal points of the working and counters electrodes of a potentisostat, and immersed in the solution together with a reference electrode, establishing a novel electrochemical measurement system. In this system, the variation of pH-controllable interface potential at the pH-sensing film/solution interface can be converted to current response when amperometry technique is employed. Based on this unique current–potential relationship, a pH-controllable switch is designed to monitor the protonation and deprotonation reaction of pH-sensing molecule. The current direction interchanges between positive and negative via pH control, illustrating a reversible conformation transition between protonated state and deprotionated state of molecule. The magnitude of current value represents the degree of protonation and deprotonation reaction of molecule. The strategy is successfully demonstrated with a remarkably reversible polyaniline-based pH-controllable switch, which confirms the feasibility of the novel electrochemical measurement system as switching transducer for designing electrochemical pH-controllable switches. This study may open up a potential avenue to construct the electrochemical pH-controllable switches.     

Celestine blue as a new indicator in electrochemical DNA biosensors

Celestine blue(CB)was introduced as a new electroactive indicator in DNA biosensors.The interaction of CB with DNA was investigated by electrochemical and spectroscopic methods.The effect of buffer kind and p H on the electrochemical behavior of CB was studied.The peak currents of CB were linearly related to DNA concentration in the range of 5.0×10~(-9) to 1.0×10~(-7)mol/L.The detection limit of this approach was 4.76×10~(-10) mol/L.Based on spectrometry data a hypochromic effect was observed in UV-Vis spectra of CB with increasing DNA concentration.The results illustrate the possible interaction mode between CB and DNA is electrostatic binding.     

3-D nanoporous gold thin film for the simultaneous electrochemical determination of dopamine and ascorbic acid

In this study, we demonstrated a novel fabrication method of three dimensional nanoporous gold thin film (NPGF) onto gold (Au) substrate using electrochemical deposition method. Scanning electron microscope (SEM) investigation reveals the formation of highly-ordered pores, approximately 30 nm in diameter and 150 nm thick. The NPGF-modified electrode shows a linear range (0.1–40 μM) for dopamine detection in the presence of ascorbic acid. The electrochemical measurements of mixtures of dopamine, ascorbic acid, and uric acid in human serum sample for real sample applications was also investigated based on differential pulse voltammetry (DPV) technique. These high sensitivity and selectivity features of the proposed NPGF biosensor offer great promise for real sample biosensor application.