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Crystal habits of LiMn2O4 and their influence on the electrochemical performance
No full textCrystal habits of LiMn2O4 prepared through a sol–gel method using different starting materials (metal acetates and metal nitrates) are studied using a crystal shape algorithm. Density functional theory (DFT) as implemented in VASP is employed to study the thermodynamic stabilities and the electronic structure of the different hkl planes of LiMn2O4, as identified by the crystal shape algorithm. The crystal habit of lithium manganate prepared through the metal acetate route, LiMn2O4 (A), seems to possess a higher
thermodynamic stability compared to the metal nitrate route viz. LiMn2O4 (N). Electrochemical cycling measurements show that the capacity retention in LiMn2O4 (A) is better than LiMn2O4 (N) at low (C/10) as well as at higher (5C) rate
Optimization of the process parameters for the removal of boron from drinking water by electrocoagulation – a clean technology
No full textBACKGROUND: There are a number of articles related to removal of boron by electrocoagulation using aluminium electrodes,
but there are fewer articles describing the use of magnesium as the anode material. The main disadvantage of aluminium
electrodes is the residual aluminium present in the treated water due to cathodic dissolution,which can create health problems.
In the case of magnesium electrodes, there is no such disadvantage. This paper presents the results of studies on the removal
of boron using magnesium and stainless steel as anode and cathode, respectively.
RESULTS: Results show that a maximum removal efficiency of 86.32% was achieved at a current density of 0.2 A dm−2 and
pH of 7 using magnesium as the anode and stainless steel as the cathode. The adsorption of boron fitted the Langmuir
adsorption isotherm, suggesting monolayer coverage of adsorbed molecules. The adsorption process follows second-order
kinetics. Temperature studies showed that adsorption was endothermic and spontaneous in nature.
CONCLUSIONS: The magnesium hydroxide generated in the cell remove the boron present in the water and reduced to a
permissible level and making it drinkable. The process scale up results was consistent with the results obtained from the
laboratory scale, showing the robustness of the process
A novel nanosilver/nafion composite electrode for electrochemical sensing of methyl parathion and parathion
No full textA novel nanosilver/nafion composite electrode was fabricated and used for sensing methyl parathion and
parathion for the first time. This electrode offers lower reduction potential and higher sensing current.
Reproducible response for four successive measurements was observed. The maximum sensing current
was obtained in 30 s for various concentrations of pesticides
Understanding the Reactivity Properties of Aun (6 e n e 13) Clusters Using Density Functional Theory Based Reactivity Descriptors
No full textRelativistic density functional theory (DFT) based calculations have been performed on gold clusters with
six to thirteen atoms (Aun; n ) 6-13). The ground state geometries of these clusters as obtained from our
calculations are presented and discussed. This work proposes that atoms in a ground state conformation can
be classified into distinct types of reactive sites in a given geometry. Based on symmetry, susceptibility of
various types of reactive sites in the ground state geometry toward an impending electrophilic and/or a
nucleophilic attack has also been studied using DFT based reactivity descriptors. The studies have also been
extended to high energy isomers in these cluster sizes. The reactivity of various sites as a function of cluster
size and shape was thus analyzed. The study shows that as a general rule the size and shape of the cluster
influences the number and position of available sites for an electrophilic and/or nucleophilic attack. This
makes the reactivity patterns of these clusters highly complex. The study also highlights as to how for a
cluster with seven atoms (Au7) various conformations are likely to coexist indicating that the reactivity patterns
of various high energy conformations are also important while dealing with small sized Au clusters
Role of Halides on the Passivation of Iron in Alkaline Buffer Solutions
No full textCyclic voltammetric studies were carried out on pure iron in alkaline borate and
phosphate buffer solutions at pH 10.8. At higher potentials, on anodic polarization, iron
forms FeB4O7 and FeOOH in borate buffer, and FeHPO4 in phosphate buffer which got
converted to higher valency phosphates.
In phosphate solutions, in presence of halides, the interfacial diffusion layer turned to be
cation selective outer sublayer and an anion selective inner sublayer, and in borate
solutions a precipitate layer of metal oxyhydroxide was formed, which was anion
selective, and anions adsorb on this
Synthesis of LiMn2O4 by molten salt technique
No full textLithium manganese oxide powders have been
successfully prepared by a molten salt synthesis using
eutectic mixture of LiCl and MnO2 salt at 900 °C. The
synthesis was performed in open atmosphere. The crystalline
powders were characterized for their phase identification
using X-ray diffraction analysis. The physicochemical
properties of the lithium manganese oxide powders are
investigated by thermal analysis (thermo gravimetric
analysis/ differential thermal analysis), Fourier transform
infrared spectroscopy, Raman spectroscopy, atomic absorption
spectroscopy, electron spin resonance spectroscopy,
and scanning electron microscopy. This work shows the
feasibility for obtaining lithium manganese oxide at lowtemperature
molten salt flux method
A Durable PEFC with Carbon-Supported Pt–TiO2 Cathode: A Cause and Effect Study
No full textDurability is central to the commercialization of polymer electrolyte fuel cells (PEFCs). The incorporation of TiO2 with platinum
(Pt) ameliorates both the stability and catalytic activity of cathodes in relation to pristine Pt cathodes currently being used in
PEFCs. PEFC cathodes comprising carbon-supported Pt–TiO2 (Pt–TiO2/C) exhibit higher durability in relation to Pt/C cathodes
as evidenced by cell polarization, impedance, and cyclic voltammetry data. The degradation in performance of the Pt–TiO2/C
cathodes is 10% after 5000 test cycles as against 28% for Pt/C cathodes. These data are in conformity with the electrochemical
surface area and impedance values. Pt–TiO2/C cathodes can withstand even 10,000 test cycles with nominal effect on their
performance. X-ray diffraction, transmission electron microscope, and cross-sectional field-emission-scanning electron microscope
studies on the catalytic electrodes reflect that incorporating TiO2 with Pt helps in mitigating the aggregation of Pt particles and
protects the Nafion membrane against peroxide radicals formed during the cathodic reduction of oxygen
PEDOT–PSSA as an alternative support for Pt electrodes in PEFCs
No full textPoly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported
platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT–PSSA
support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and
ionic (H+-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of
PEDOT–PSSA composite also helps reducing Nafion content in PEFC electrodes. During prolonged operation
of PEFCs, Pt electrodes supported onto PEDOT–PSSA composite exhibit lower corrosion in relation to Pt
electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT–
PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy,
scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT–PSSA-supported Pt
catalyst electrodes offer a peak power-density of 810 mW cm–2 at a load current-density of 1800 mA cm–2 with
Nafion content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative
support for platinized PEFC electrodes
Synthesis of macroporous LiMn2O4 with avian egg membrane as a template
No full textAvian eggshell membrane as a template for the
synthesis of a macroporous network of crystalline LiMn2O4
is demonstrated. Well-formed crystals of average size
600 nm formed a network structure whose average pore
size was 2–4 μm. The unique porous structure should make
it an attractive cathode material for lithium-ion batteries. In fact, for an 80% cutoff in capacity retention, LiMn2O4
obtained by a 10-h calcination at 800°C sustained 83
cycles
Effect of some pare earth elements on dry matter partitioning, nodule formation and chlorophyll content in Arachis hypogaea L. plants
No full textRare earth elements (REE) are found to be beneficial to plants in order to improve crop yield. The present study reveals the response of
leguminous plant (Arachis hypogaea L.) to monazite soil containing Rare earth elements (Lanthanum and Samarium). This particular
study explains the effects of rare earths on factors such as growth, total leaf chlorophyll content, number of root nodules and nitrogenase
activity of groundnut plant. A significant increase in plant biomass and total chlorophyll content are observed. The increase in number of
root nodules and the nitrogenase activity (Acetylene reduction, 20.72 n moles C2H4 formed / h/ g fresh nodules) were observed in the
plants exposed to REEs. A profound effect of Lanthanum and Samarium present in the rare earth soil on the chlorophyll content, amylase
activity, SOD and POD level were noticed