Polymer template-assisted microemulsion synthesis of large surface area, porous Li2MnO3 and its characterization as a positive electrode material of Li-ion cells

Lithium-rich manganese oxide (Li2MnO3) is prepared by reverse microemulsion method employing Pluronic acid (P123) as a soft template and studied as a positive electrode material. The as-prepared sample possesses good crystalline structure with a broadly distributed mesoporosity but low surface area. As expected, cyclic voltammetry and charge-discharge data indicate poor electrochemical activity. However, the sample gains surface area with narrowly distributed mesoporosity and also electrochemical activity after treating in 4 M H2SO4. A discharge capacity of about 160 mAh g(-1) is obtained. When the acid-treated sample is heated at 300 A degrees C, the resulting porous sample with a large surface area and dual porosity provides a discharge capacity of 240 mAh g(-1). The rate capability study suggests that the sample provides about 150 mAh g(-1) at a specific discharge current of 1.25 A g(-1). Although the cycling stability is poor, the high rate capability is attributed to porous nature of the material.

High catalytic activity of Au-PEDOT nanoflowers toward electrooxidation of glucose

Electrochemically deposited porous film of poly(3,4-ethylenedioxythiophene) (PEDOT) on carbon paper current collector is used as the substrate for electrochemical deposition of Au. PEDOT facilitates the formation of Au nanoflowers with an enhanced electrochemical active surface area, when compared with sub-micron size Au particles deposited on bare carbon paper electrode. Owing to enhanced surface area of Au nanoflowers, the Au-PEDOT/C electrode shows greater activity than Au/C electrode toward electrooxidation of glucose in 0.5 M NaOH electrolyte. Cyclic voltammetry studies show that the peak current density increases with increase in concentrations of glucose and NaOH in the electrolyte. H-1-NMR spectroscopy data indicates that sodium formate and gluconate are the primary products of electrooxidation of glucose on Au-PEDOT/C electrode. Repetitive cyclic voltametry and amperometry studies suggest that the electrochemical stability of Au-PEDOT/C electrode is higher than that of Au/C electrode. Thus, electrochemically deposited nanostructured Au on PEDOT/C is an efficient catalyst for direct glucose oxidation in alkaline media. (C) 2013 The Electrochemical Society. All rights reserved.

On Using Nanoporous Alumina Films as Tribological Coating

Anodization of aluminum alloys is a common surface treatment procedure employed for the protection against corrosion. A thin amorphous layer of alumina is formed on the surface of alloy, which seals the alloy surface from the surrounding. This alumina layer being harder than the base aluminum alloy can be useful as a tribological coating. But since this alumina layer is randomly formed with disordered voids and pores, predicting the mechanical properties is difficult. Specific anodizing conditions can be used to form highly ordered anodic nanoporous alumina films 1] on the aluminum alloy surface. These nanoporous alumina layer can be effectively used as a tribological coating, because of the highly ordered controllable geometry and the empty pores which can be used as reservoirs for lubricant.

Highly Stable Hexacoordinated Nonoxidovanadium(IV) Complexes of Sterically Constrained Ligands: Syntheses, Structure, and Study of Antiproliferative and Insulin Mimetic Activity

Three highly stable, hexacoordinated nonoxidovanadium(IV), V-IV(L)(2), complexes (1-3) have been isolated and structurally characterized with tridentate aroylhydrazonates containing ONO donor atoms. All the complexes are stable in the open air in the solid state as well as in solution, a phenomenon rarely observed in nonoxidovanadium(IV) complexes. The complexes have good solubility in organic solvents, permitting electrochemical and various spectroscopic investigations. The existence of nonoxidovanadium(IV) complexes was confirmed by elemental analysis, ESI mass spectroscopy, cyclic voltammetry, EPR, and magnetic susceptibility measurements. X-ray crystallography showed the N3O3 donor set to define a trigonal prismatic geometry in each case. All the complexes show in vitro insulin mimetic activity against insulin responsive L6 myoblast cells, with complex 3 being the most potent, which is comparable to insulin at the complex concentration of 4 mu M, while the others have moderate insulin mimetic activity. In addition, the in vitro antiproliferative activity of complexes 1-3 against the He La cell line was assayed. The cytotoxicity of the complexes is affected by the various functional groups attached to the bezoylhydrazone derivative and 2 showed considerable antiproliferative activity compared to the most commonly used chemotherapeutic drugs.

Enhanced electrochemical performance of graphene nanosheet thin film anode decorated with tin nanoparticles

Graphene nanosheet (GNS) was synthesized by using microwave plasma enhanced CVD on copper substrate and followed by evaporation of tin metal. Scanning and transmission electron microscopy show that nanosize Sn particles are well embedded into the GNS matrix. The composition, structure, and electrochemical properties were characterized by X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), cyclic voltammetry (CV) and chrono-potentiometry. The first discharge capacity of as-deposited and annealed SnGNS obtained was 1551 mA h/g and 975 mA h/g, respectively. The anodes show excellent cyclic performance and coulombic efficiency.

Self-assembly of discrete metallamacrocycles employing half-sandwich octahedral diruthenium(II) building units and imidazole-based ligands

Equimolar combination of a series of binuclear half-sandwich p-cymene ruthenium(II) building units Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1a](OTf)(2), Ru-2(mu-eta(4)-N,N'-diphenyloxamidato)( MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1b](OTf)(2) and Ru-2(mu-eta(4)-C6H2O4)(MeOH)(2)(eta(6)-p-cymene)(2)](OTf)(2) 1c](OTf)(2) separately with imidazole-based ditopic ligands (L-1-L-2) in methanol yielded a series of tetranuclear metallamacrocycles 2-7](OTf)(4), respectively L-1 = 1,4-bis(imidazole-1-yl)benzene; L-2 = 4,4'-bis(imidazole-1-yl)biphenyl; OTf- = O3SCF3-]. Similarly, the reaction of Ru-2(mu-eta(4)-C2O4)(MeOH)(2)(eta(6)-p-cymene)2](OTf)(2) 1a](OTf)(2) with a triazine-based tritopic ligand 1,3,5-tris(imidazole-1-yl) triazine (L3) in 3: 2 M ratio afforded an unexpected tetranuclear macrocycle 8](OTf)(4) instead of an expected trigonal prismatic cage 8a](OTf)(6). All the self-assembled macrocycles 2-8](OTf)(4) were isolated in moderate to high yields and were fully characterized by multinuclear H-1, F-19] NMR, IR and electrospray ionization mass spectrometry (ESI-MS). In addition, X-ray diffraction study on the single crystals of 3](OTf)(4) and 8](OTf)(4) also indicated the formation 2 + 2] self-assembled macrocycles. Despite the possibility of formation of different conformational isomeric macrocycles (syn-and anti) and polymeric product due to free rotation of ligand sites of imidazole linkers, the selective formation of single conformational isomer (anti) as the only product is quite interesting. Furthermore, the photo-and electrochemical properties of these assemblies have been studied using UV/Vis absorption and cyclic voltammetry analysis. (c) 2013 Elsevier B.V. All rights reserved.

Optical, Electrochemical, and Structural Properties of Spray Coated Dihexyl Substituted Poly (3,4 propylene dioxythiophene) Film for Optoelectronics Devices

The dihexyl substituted poly (3,4-propylenedioxythiophene) (PProDOT-Hx(2)) thin films uniformly deposited by cost effective spray coating technique on transparent conducting oxide coated substrates. The electro-optical properties of PProDOT-Hx(2) films were studied by UV-Vis spectroscopy that shows the color contrast about 45% with coloration efficiency of approximate to 185cm(2)/C. The electrochemical properties of PProDOT-Hx(2) films were studied by cyclic voltammetry and AC impedance techniques. The cyclic voltammogram shows that redox reaction of films are diffusion controlled and ions transportation will be faster on the polymer film at higher scan rate. Impedance spectra indicate that polymer films are showing interface charge transfer process as well as capacitive behavior between the electrode and electrolyte. The XRD of the PProDOT-Hx(2) thin films revealed that the films are in amorphous nature, which accelerates the transportation of ions during redox process.

Pristine and graphitized-MWCNTs as durable cathode-catalyst supports for PEFCs

Long-term deterioration in the performance of PEFCs is attributed largely to reduction in active area of the platinum catalyst at cathode, usually caused by carbon-support corrosion. Multi-walled carbon-nanotubes (MWCNTs) as cathode-catalyst support are found to enhance long-term stability of platinum catalyst (Pt) in relation to non-graphitic carbon. In addition, highly graphitic MWCNTs (G-MWCNTs) are found to be electrochemically more stable than pristine MWCNTs. This is because graphitic-carbon-supported-Pt (Pt/MWCNTs) cathodes exhibit higher resistance to carbon corrosion in-relation to non-graphitic-carbon-supported-Pt (Pt/C) cathodes in PEFCs during accelerated stress-test (AST) as evidenced by chronoamperometry and carbon dioxide studies. The corresponding change in electrochemical surface area (ESA), cell performance, and charge-transfer resistance are monitored through cyclic voltammetry, cell polarization, and impedance measurements, respectively. The extent of crystallinity, namely amorphous or graphitic nature of the three supports, is examined by Raman spectroscopy. X-ray diffraction and transmission electron microscopy studies both prior and after AST suggest lesser deformation in catalyst layer and catalyst particles for Pt/G-MWCNTs and Pt/MWCNTs cathodes in relation to Pt/C cathodes, reflecting that graphitic carbon-support resists carbon corrosion and helps mitigating aggregation of Pt particles. It is also found that with increasing degree of graphitization, the electrochemical stability for MWCNTs increases due to the lesser surface defects.

Evolution of Surface Roughness During Electropolishing

The characteristics of surface roughness span a range of length scales determined by the nature of the surface generation process. The mechanism by which material is removed at a length scale determines the roughness at that scale. Electropolishing preferentially reduces the peaks of surface protuberances at sub-micron length scales to produce smooth surfaces. The material removal in electropolishing occurs by two different mechanisms of anodic leveling and microsmoothing. Due to insufficient lateral resolution, individual contribution of these two mechanisms could not be measured by conventional roughness measurement techniques and parameters. In this work, we utilize the high lateral resolution offered by Atomic force microscopy along with the power spectral density method of characterization, to study the evolution of roughness during electropolishing. The power spectral density show two corner frequencies indicating the length scales over which the two mechanisms operate. These characteristic frequencies are found to be a function of the electropolishing time and hence can be used to optimize the electropolishing process.

Electrodeposition of Ag-Ni-Fe Nanowires

Present work provides an electrodeposition based methodology for synthesizing Ag-Ni-Fe nanowires. Nanowire morphology was achieved by using an anodic alumina membrane having cylindrical pores of similar to 200 nm diameter. Compositional analysis at a single nanowire level revealed a fairly uniform distribution of component elements in the nanowire volume. Structural characterization strongly indicated toward a presence of randomly oriented, non-equilibrium, nano-crystalline phase volume inside the nanowires. Magnetic characterization revealed a soft magnetic character for the as-synthesized Ag-Ni-Fe nanowires. (C) 2014 The Electrochemical Society. All rights reserved.

Coconut kernel-derived activated carbon as electrode material for electrical double-layer capacitors

Carbonization of milk-free coconut kernel pulp is carried out at low temperatures. The carbon samples are activated using KOH, and electrical double-layer capacitor (EDLC) properties are studied. Among the several samples prepared, activated carbon prepared at 600 A degrees C has a large surface area (1,200 m(2) g(-1)). There is a decrease in surface area with increasing temperature of preparation. Cyclic voltammetry and galvanostatic charge-discharge studies suggest that activated carbons derived from coconut kernel pulp are appropriate materials for EDLC studies in acidic, alkaline, and non-aqueous electrolytes. Specific capacitance of 173 F g(-1) is obtained in 1 M H2SO4 electrolyte for the activated carbon prepared at 600 A degrees C. The supercapacitor properties of activated carbon sample prepared at 600 A degrees C are superior to the samples prepared at higher temperatures.

Synthesis and characterization of Ag-Co-Ni nanowires

This work provides an electrodeposition-based methodology for synthesizing multicomponent nanowires containing Ag, Co and Ni atoms. Nanowire morphology was obtained by using an anodic alumina membrane with cylindrical pores of similar to 200-nm diameter. Structural, compositional and magnetic characterization revealed that the as-synthesized nanowires adopted a core-shell microstructure. The core (axial region) contained pure Ag phase volumes with a plate-like morphology oriented perpendicular to the nanowire axis. The shell (peripheral region) contained pure Ag nanoparticles along with superparamagnetic Co and Ni rich clusters.

Electron microscopy of Ag-(Ni-O) core-shell nanowires

This report provides information about an electrodeposition based two-step synthesis methodology for producing core-shell Ag-(Ni-O) nanowires and their detailed structural and compositional characterization using electron microscopy technique. Nanowires were produced by employing anodic alumina templates with a pore diameter of 200 nm. In the first step of the synthesis process, nanocrystalline Ni-O was electrodeposited in a controlled manner such that it heterogeneously nucleated and grew only on the template pore walls without filling the pores from bottom upwards. This alumina template with pore walls coated with Ni-O was then utilized as a template during the electrodeposition of Ag in the second step. Electrodeposited Ag filled the template pores to finally produce Ag-(Ni-O) core-shell nanowires with an overall diameter of 200 nm.

Reduced graphene oxide-supported nickel oxide catalyst with improved CO tolerance for formic acid electrooxidation

The superior catalytic activity along with improved CO tolerance for formic acid electro-oxidation has been demonstrated on a NiO-decorated reduced graphene oxide (rGO) catalyst. The cyclic voltammetry response of rGO-NiO/Pt catalyst elucidates improved CO tolerance and follows direct oxidation pathway. It is probably due to the beneficial effect of residual oxygen groups on rGO support which is supported by FT-IR spectrum. A strong interaction of rGO support with NiO nanoparticles facilitates the removal of CO from the catalyst surface. The chronoamperometric response indicates a higher catalytic activity and stability of rGO-NiO/Pt catalyst than the NiO/Pt and unmodified Pt electrode catalyst for a prolonged time of continuous oxidation of formic acid. Copyright (C) 2014, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.

Ag nanoparticles-anchored reduced graphene oxide catalyst for oxygen electrode reaction in aqueous electrolytes and also a non-aqueous electrolyte for Li-O-2 cells

Silver nanoparticles-anchored reduced graphene oxide (Ag-RGO) is prepared by simultaneous reduction of graphene oxide and Ag+ ions in an aqueous medium by ethylene glycol as the reducing agent. Ag particles of average size of 4.7 nm were uniformly distributed on the RGO sheets. Oxygen reduction reaction (ORR) is studied on Ag-RGO catalyst in both aqueous and non-aqueous electrolytes by using cyclic voltammetry and rotating disk electrode techniques. As the interest in non-aqueous electrolyte is to study the catalytic performance of Ag-RGO for rechargeable Li-O-2 cells, these cells are assembled and characterized. Li-O-2 cells with Ag-RGO as the oxygen electrode catalyst are subjected to charge-discharge cycling at several current densities. A discharge capacity of 11 950 mA h g(-1) (11.29 mA h cm(-2)) is obtained initially at low current density. Although there is a decrease in the capacity on repeated discharge-charge cycling initially, a stable capacity is observed for about 30 cycles. The results indicate that Ag-RGO is a suitable catalyst for rechargeable Li-O-2 cells.