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Molybdenum oxide (MoO3) thin film based electrochromic cell characterisation in 0.1 M LiClO4.PC electrolyte
No full textElectrochromic thin films of molybdenum oxide (MoO3) were prepared on transparent conducting
oxide substrates, i.e. fluorine doped tin oxide coated (FTO or SnO2:F) glass substrates by
electron beam evaporation technique using pure MoO3 (99?99%) pellets at various substrate
temperatures (i.e. Tsub5room temperature (30uC), 100 and 200uC) under the vacuum of
161025 mbar. The room temperature prepared films were further annealed Tanne at 200 and
300uC for about one hour in the vacuum environment. The electrochemical nature of the films was
studied by the cyclic voltammetry technique using a three electrode electrochemical cell in 0?1M
LiClO4.PC electrolyte. The performance of the films was also tested by making electrochromic
cells. The films produced at higher substrate temperature show lesser modulation in the visible
spectrum, compared with the films produced at lower temperatures. A maximum colouration
efficiency of 66 cm2 C21 was observed in the infrared region for the films prepared at room
temperature
Photoelectrochemical properties of pulse electrodeposited cadmium selenide films
No full textCdSe films were deposited by the pulse plating technique in the presence of silicotungstic
acid.The films deposited in the presence of silicotungstic acid exhibited hexagonal
structure. The films exhibited a direct band gap of 1.67 eV. With addition of
silsicotungstic acid, the average grain size decreased from 17.1 nm to 11.7 nm, and the
grain became more homogeneous.The surface roughness decreased from 2.83 nm to 1.97
ater adding silicotungstic acid.The efficiency of the photoelectrochemical cells increases
with addition of silico-tungstic acid
Preparation, corrosion and structural properties of Cu–Ni multilayers from sulphate/citrate bath
No full textPotentiostatic electrodeposition was used to produce Cu–Ni multilayer by two-wave pulse plating technique
from sulphate/citrate electrolyte at pH 4. Cyclic voltammetry studies provide information about
the deposition potential. The compositions of multilayers were studied using X-ray fluorescence (XRF).
Electrochemical corrosion studies of the deposited multilayer on copper were studied by potentiodynamic
polarization and electrochemical impedance spectroscopy (EIS). The surface of the layer having
smooth, small grain and compact structure was confirmed by scanning electron microscopy (SEM) and
atomic force microscopy (AFM) analysis. The face centered cubic lattices are present in the Ni–Cu multilayer
and this is confirmed by the X-ray diffraction (XRD) data. The multilayer structures have better corrosion
resistance than the base substrate
Effect of thermophilic sulphate-reducing bacteria (Desulfotomaculum geothermicum) isolated from Indian petroleum refinery on the corrosion of mild steel
No full textThe role of thermophilic sulphate-reducing bacteria
(SRB) Desulfotomaculum geothermicum in mild steel
corrosion was evaluated by electrochemical study and
surface analysis technique. In the presence of D. geothermicum,
the corrosion rate was 0.0698 mmpy at
50°C, which was higher when compared to control.
Polarization study revealed that the bacteria enhanced
cathodic reaction and suppressed anodic reaction.
XRD data revealed that the presence of FeS enhanced
the cathodic reaction by the formation of a protective
film on the metal surface. Pitting was observed by
confocal microscopy, which may be due to cathodic
depolarization. The study implicates the importance
of D. geothermicum in the corrosion of cooling towers
of the petroleum refinery
Microwave assisted synthesis and electrochemical behaviour of LiMg0.1Co0.9O2 for lithium rechargeable batteries
No full textLayered LiMg0.1Co0.9O2 has been synthesized using microwave assisted solution technique. The precursor
has been subjected to thermo-gravimetric/differential thermal analysis (TG/DTA) and calcined at 850 ◦C.
The precursor and the calcined powders were characterized by X-ray diffraction (XRD) to confirm the
formation of single-phase layered material. Fourier transform infrared (FTIR) studies were carried out
to understand the nature of the metal–ligand bond and the observations were consistent with the XRD
spectrum. Scanning (SEM) and transmission electron microscope (TEM) images have been obtained to
understand the surface morphology and the grain orientation of the synthesized material. Coin cells of
2016 type have been assembled using the synthesized layered material as the cathode active material,
lithium foil as the counter and reference electrodes and 1M LiPF6 in 1:1 EC/DEC as the electrolyte. Coin
cellswere assembled and crimp sealed inside an argon filled glove box. The charge/discharge characteristics
of the coin cellswere evaluated galvanostatically in the potential range 2.7–4.3 V. Results indicate that
LiMg0.1Co0.9O2 delivers an average discharge capacity of∼135mAhg−1 over the investigated 20 cycles and
is a potential candidate for use as cathode material in lithium rechargeable cells
Novel Self-Supported Natural and Synthetic Polymer Membranes for Air Humidification
No full textNovel self-supported natural and synthetic
polymer membranes of chitosan-hydroxy ethyl cellulosemontmorillonite
(CS-HEC-MMT) and polyvinyl alcohol
(PVA)-polystyrene sulfonic acid (PSSA) are prepared by solution
casting method followed by crosslinking. These
membranes are employed for air humidification at varying
temperatures between 30C and 70C and their performances
are compared with commercial Nafion
VR
membranes.
High water fluxes with desired humidified-air output have
been achieved for CS-HEC-MMT and PVA-PSSA hybrid
membranes at air-flow rates of 1–10 slpm. Variation in the
air/water mixing ratio, dew point, and relative humidity
that ultimately results in desired water flux with respect to air-flow rates are also quantified for all the membranes.
Water flux values for CS-HEC-MMT are less than those for
Nafion VR and PVA-PSSA membranes, but the operational stability of CS-HEC-MMT membrane is higher than PVAPSSA
and comparable with Nafion VR both of which can operate
up to 70C at repetitive cycles of humidification
Carbon-Supported Pt–TiO2 as a Methanol-Tolerant Oxygen-Reduction Catalyst for DMFCs
No full textCarbon-supported Pt–TiO2 Pt–TiO2/C catalysts with varying at. wt ratios of Pt to Ti, namely, 1:1, 2:1, and 3:1, are prepared by
the sol–gel method. The electrocatalytic activity of the catalysts toward oxygen reduction reaction ORR, both in the presence and
absence of methanol, is evaluated for application in direct methanol fuel cells DMFCs. The optimum at. wt ratio of Pt to Ti in
Pt–TiO2/C is established by fuel cell polarization, linear sweep voltammetry, and cyclic voltammetry studies. Pt–TiO2/C heattreated
at 750°C with Pt and Ti in an at. wt ratio of 2:1 shows enhanced methanol tolerance, while maintaining high catalytic
activity toward ORR. The DMFC with a Pt–TiO2/C cathode catalyst exhibits an enhanced peak power density of 180 mW/cm2
in contrast to the 80 mW/cm2 achieved from the DMFC with carbon-supported Pt catalyst while operating under identical
conditions. Complementary data on the influence of TiO2 on the crystallinity of Pt, surface morphology, and particle size, surface
oxidation states of individual constituents, and bulk and surface compositions are also obtained by powder X-ray diffraction,
scanning and transmission electron microscopy, X-ray photoelectron spectroscopy, energy dispersive analysis by X-ray, and
inductively coupled plasma optical emission spectrometry
Preparation of catalytic films of platinum on Au substrates modified by self-assembled PAMAM dendrimer monolayers
No full textIn this work we demonstrate the preparation of highly catalytically active Pt formed by the galvanic
replacement of the copper adlayer on Au substrates, modified by the self-assembly of fourth generation
amine terminated PAMAM dendrimer (G4NH2). The copper adlayer was formed on the dendrimermodified
gold substrate by chemical preconcentration of copper ions followed by electrochemical
reduction. The Pt overlayer was characterized by SEM, XPS and by cyclic voltammetry. The catalytic
efficiency of the modified film thus prepared through soft route was evaluated by the electro catalytic
oxidation of methanol using cyclic voltammetry, chronoamperometry and AC impedance techniques.
This work also demonstrates that the copper adlayer formed on the dendrimer-modified electrode can
undergo galvanic replacement by nobler metals like Au and Ag, besides Pt. An elegant soft route involving
a new three-step protocol to build the concentration of active Pt on the Au surface has been developed.
Concentration of the same metal (Pt) or two different metals (Pt–Au) can be built at the interface in a
stepwise manner at ambient temperature
An alternative approach to selective sea water oxidation for hydrogen production
No full textSea water electrolysis is one of the promising ways to produce hydrogen since it is available in plentiful
supply on the earth. However, in sea water electrolysis toxic chlorine evolution is the preferred reaction
over oxygen evolution at the anode. In this work, research has been focused on the development of electrode
materials with a high selectivity for oxygen evolution over chlorine evolution. Selective oxidation in
sea water electrolysis has been demonstrated by using a cation-selective polymer. We have used a permselective
membrane (Nafion), which electrostatically repels chloride ions (Cl) to the electrode surface
and thereby enhances oxygen evolution at the anode. The efficiency and behaviour of the electrode have
been characterized by means of anode current efficiency and polarization studies. The surface morphology
of the electrode has been characterized by using a scanning electron microscope (SEM). The results
suggest that nearly 100% oxygen evolution efficiency could be achieved when using an IrO2/Ti electrode
surface-modified by a perm-selective polymer
Direct Oxidation of Dimethylsulphoxide and Reduction of Maleic Acid in Methanesulphonic Acid Medium
No full textThe direct electro oxidation of dimethylsulphoxide (DMSO) to dimethylsulphone
(DMSO2) at a Pb/PbO2 anode and electro reduction of maleic acid (MA)
to succinic acid (SA) at stainless steel cathode have been has been carried out in
methane sulphonic acid (MSA) medium in a batch divided cell. It is to be noted
that, as methane sulphonic acid medium (MAS) is biodegradable, it is a preferred
medium for the electrochemical reactions.
The process parameters such as concentration of MSA, DMSO and current density
have been critically examined and the comparative performances of Pb/PbO2
with TSIA electrode as well as the reusing of electrolyte under optimum conditions
have been investigated. The reaction parameters such as acid concentration,
current density, the use of divided and undivided cells, etc. have been studied on
electrochemical reduction of MA to SA.
In the case of direct electro oxidation of dimethylsulphoxide to dimethylsulphone,
the current efficiency on TSIA anode has been around 60- 65% while that with
Pb/PbO2 has been more than 90%. The electro reduction of MA to SA has given
current efficiency around 65 – 70%. Based on the result obtained on trials, the
optimum parameters of the reaction found to be 1.0 M acid concentration and 5.0
A dm−2 current density. Divided cell has given good results when compared to
undivided cell