Preparation and electrochemical characterization of a new NiMoO4 catalyst for electrochemical O2 evolution

The NiMoO₄ catalyst has been obtained by a precipitation method under a controlled pH condition and characterized ex situ by infrared, X-ray diffraction, Brunauer–Emmett–Teller (BET), and particle size, and in situ by cyclic voltammetry, impedance and steady-state anodic Tafel polarization techniques. Results show that NiMoO₄ has pure crystalline monoclinic phase with the crystallite size ~50 nm and the lattice constants, a?=?9.597 Å, b?=?8.765 Å, c?=?7.667 Å, and β?=?114.22°. Values of the average particle size and BET surface area of the oxide powders are found to be 730 nm and 11.75 m²/g, respectively. The oxygen evolution reaction follows the first-order kinetics with respect to OH^? concentration, the Tafel slope being ~70 mV.     

Fabrication of catalyst-coated membrane by modified decal transfer technique

A decal transfer method based on colloidal ink was developed for the fabrication of membrane electrode assemblies (MEAs). The new method requires fewer steps and utilizes H⁺ form of membrane compared to conventional decal method based on solution ink utilizing Na⁺ form of membrane. The structural features of the electrodes made by the modified decal method were investigated by scanning electron microscopy (SEM). The performance of fabricated electrode was evaluated for oxygen reduction reaction in a proton exchange membrane fuel cell. The results indicate that the modified decal method has the potential to be a facile method of fabricating electrodes with high performance.     

Thermolytic investigations on nickel(II) complexes of 4‐N‐(4′‐antipyrylmethylidene)aminoantipyrine with various counterions

Phenomenological characteristics and kinetic and mechanistic aspects of the thermal decomposition of nitrate, chloride, bromide, and iodide complexes of nickel(II) with 4‐N‐(4′‐antipyrylmethylidene)aminoantipyrine have been studied using thermogravimetric (TG) and differential thermogravimetric (DTG) techniques. Kinetic parameters such as activation energy, preexponential factor, and entropy of activation were quantified. The rate‐controlling process in all stages of decomposition was found to be based on random nucleation with one nucleus on each particle according to the Mampel model. © 2006 Wiley Periodicals, Inc. Int J Chem Kinet 39: 53–58, 2007     

COMPARE: A computer program for comparative analysis of EPR data for low-symmetry paramagnetic centers

A quantitative method has been proposed for comparative analysis of EPR (electron para-magnetic resonance) data for low-symmetry paramagnetic centers and a computer program, COMPARE, based on this method has been developed. Quantitative parametersS _A andS _D are introduced to describe the closeness of the orientation of any two-axis systems and the principal values of any two tensors, respectively. The method helps to identify the pairs of data sets, comprising the principal values as well as the orientations of the principal axes of the second-rank spin Hamiltonian terms, which may likely belong to the same physical center but have been ascribed to distinct centers. Other useful applications of the program COMPARE are briefly discussed.     

Enantioselective Formal C(sp2)−H Vinylation

An enantioselective formal C(sp²)?H vinylation of prochiral 2,2‐disubstituted cyclopentene‐1,3‐dione is presented. This vinylative desymmetrization is realized by using a two‐step procedure that consists of a catalytic enantioselective vinylogous Michael addition of deconjugated butenolides to cyclopentene‐1,3‐dione and a base‐mediated decarboxylation. The overall process utilizes deconjugated butenolides as the source of the highly substituted vinyl unit. Five‐membered carbocycles containing a remote all‐carbon quaternary stereogenic center are obtained in good yields and with good to high enantioselectivities.     

Microchip capillary electrophoresis with amperometric detection for rapid separation and detection of phenolic acids

A microchip capillary-electrophoresis protocol for rapid and effective measurements of food-related phenolic acids (including chlorogenic, gentisic, ferulic, and vanillic acids) is described. Relevant parameters of the chip separation and amperometric detection are examined and optimized. Under optimum conditions, the analytes could be separated and detected in a 15 mM borate buffer (pH 9.5, with 10% of methanol) within 300 s using a separation voltage of 2000 V and a detection voltage of +1.0 V. Linear calibration plots are observed for micromolar concentrations of the phenolic acid compounds. The negligible sample volumes used in the microchip procedure obviates surface fouling common to amperometric measurements of phenolic compounds. The new microchip protocol offers great promise for a wide range of food applications requiring fast measurements and negligible sample consumption. An application on a commercial red wine was performed with minimal sample preparation and promising results.     

Extraction-spectrophotometric determination of nickel as Ni-(PAR)2-(CTAB)2 complex in polymetallic sea-bed nodules and steels

A red, water-soluble complex of nickel with PAR can be extracted into chloroform with CTAB at pH 7.0. The system obeys Beer's law upto 0.5 g/ml with a molar absorptivity of 45 200 L·mol^–1·cm^–1 at 540 nm. Job's method of continuous variations revealed that the composition of the extracting species is 1:2:2 for nickel:PAR:CTAB. Based on this extraction, a highly sensitive and selective spectrophotometric method for the determination of nickel in polymetallic sea-bed nodules and in steels, after prior separation of iron and manganese, was developed. The standard deviation was 0.04–0.127 g for 5–25 g of nickel.     

Polyimide-epoxy alloys prepared via micro-modification: Water sorption and diffusion

A novel polyimide-epoxy or PI-EP alloys are prepared by the modification of polyamic acid in the concentration range of 1.54×10⁻⁶ to 1.54×10⁻² mol/L. The methanol sorption for these alloys at 24 hrs and at equilibrium conditions are determined and the residual solvent in fully cyclized polyimides were calculated. The presence of the residual solvent is visualized in fully imidized polymer and a structure containing partly imidized amic acid moiety is proposed and their concentration (in percentage) is calculated. The water sorption for these alloys at 24 hrs and at equilibrium conditions and the values of the water diffusion coefficient are determined from absorption isotherms. The PI-EP alloys have shown comparatively lower water sorption and higher diffusion coefficient than the unmodified polyimide. The mechanistic aspects of water sorption and diffusion are discussed.