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The effect of cathode materials on the electrochemical reduction of nitric acid
No full textElectrochemical or chemical reduction of nitric acid is a well studied area in literature due to the importance
of the products formed. The present work focuses on the effect of conventional cathode materials including
PbO
2
, amalgamated Cu, graphite, Pb, Pt and a modified electrode material Ti/ TiO
2
on the reduction of nitric
acid. Ammonia and hydroxylamine are the main products which are estimated by conventional titration
methods. Other conditions being similar, the product distribution varies quite drastically as a function of
the electrode material and Ti/ TiO
2
is found to favor a higher ratio of hydroxylamine to ammonia formation
compared to other electrodes. The conditions have also been optimized based on the maximum yield of the
product
Galvanostatic and potentiostatic fluorination of 2-indanone, 1-indanone and 1,3-indandione in Et3N 4HF medium. Adsorption effects on yield and product selectivity
No full textSelective electrochemical fluorination (SEF) of 1-indanone, 2-indanone and 1,3-indandione were carried
out in Et3N � 4HF ionic liquid. Cyclic voltammetric measurements indicated that the ionic liquid undergoes
oxidation below 2 V on platinum electrode while the background limit is extended up to 2.3 V on
glassy carbon electrode. Well defined voltammetric peaks were observed for all the three compounds
on glassy carbon electrode. Significant absorption effects were also noticed. Preparative electrolysis indicated
lower selectivity for all the three compounds under galvanostatic conditions when compared to
potentiostatic conditions. Both under galvanostatic and potentiostatic conditions, 2-indanone, which
exhibits weak adsorption, gave 1-fluoro-2-indanone with high selectivity. 1-Indanone exhibits higher
anodic oxidation potential around 2 V. 1,3-Indandione exhibited strong intermediate or product adsorption
during voltammetric measurements. The yield and selectivity were much lower for these two compounds
under galvanostatic conditions. Quite interestingly in both these cases, the selectivity close to
70% for the monofluorinated compound could be achieved under potentiostatic conditions by passing
up to 6 F/mole of electric charge. Prevention of formation of over oxidation products under potentiostatic
conditions may be the main cause for this improvement as suggested by chronoamperometric
measurements
Electroless deposition of copper from methane sulphonate complexed bath
No full textElectroless copper deposition is widely used for printed circuit applications. A new bath based on
copper methane sulphonate replacing copper sulphate, EDTA and paraformaldehyde has been
developed, which is very useful for plating on non-conductors and through hole plating in printed
circuit manufacturing processes. The new bath has a higher rate of deposition of 3?3 mm h21 than
the conventional sulphate bath (with a rate of 1?5 mm h21) and the bath stability and the quality of
the deposits are very good. Scanning electron microscopy, X-ray diffraction and atomic force
microscopy studies have been carried out and the crystallite size of the copper is measured to be
134 nm with a preferred orientation of 200 planes. The deposit obtained is pure copper and the
surface roughness is of the order of 10 nm
Removal of phosphate from agricultural soil by electrokinetic remediation with iron electrode
No full textPhosphorus is considered the limiting nutrient
in eutrophication of agricultural soil in Korea. This study
evaluates the coupled application of electrokinetic process
by iron and titanium electrodes for removal of phosphate
from agricultural soils. Experiments were conducted to
evaluate phosphate removal under the following conditions:
(I) control; (II) 1% starch addition in the soil without
EK; (III) 1% starch addition at the anolyte using a cast iron anode and a carbon cathode; (IV) no starch addition using a cast iron anode and a carbon cathode, and; (V) 1% starch at the anolyte using a titanium anode and a carbon cathode. When an iron anode was used under 0.5, 1.0 and 2.0 V/cm,the removal of phosphate was significant at 2 V/cm. The
addition of starch also helps to remove nitrate significantly using an iron electrode. The results reveal that iron electrodes result in significantly more removal compared to titanium electrodes
A solid-polymer-electrolyte direct methanol fuel cell (DMFC) with Pt–Ru nanoparticles supported onto poly(3,4-ethylenedioxythiophene) and polystyrene sulphonic acid polymer composite as anode
No full textNano-sized Pt–Ru supported onto a mixed-conducting polymer composite comprising
poly(3,4-ethylenedioxythiophene)-polystyrene sulphonic acid (PEDOT–PSSA) is employed as anode in a
solid-polymer-electrolyte direct methanol fuel cell (SPE–DMFC) and its performance compared with the
SPE–DMFC employing conventional Vulcan XC-72R carbon supported Pt–Ru anode. Physical characterization
of the catalyst is conducted by Fourier-transform infra-red (FTIR) spectroscopy, X-ray diffraction
(XRD), Scanning electron microscopy (SEM) and Energy dispersive X-ray analysis (EDAX) in
conjunction with cyclic voltammetry and chronoamperometry. The study suggests that PEDOT–PSSA to
be a promising alternative catalyst-support-material for SPE–DMFCs
Electrochlorinator for the in-situ electro synthesis of sodium hypochlorite for disinfection of water
No full textAnalysis of the electrochemical phenomenon at the rebar–concrete interface using the electrochemical impedance spectroscopic technique
No full textThe corrosion rate of rebar during the various stages where it occurs, such as passivation, initiation of corrosion
and severe corrosion, needs to be determined non-destructively for the maintenance, restoration and replacement of
concrete structures. The double layer capacitance (Cdl) and the charge transfer resistance or polarisation resistance
(Rp) of the corrosion processes have been associated with the slope of the low-frequency arc in the Nyquist plot,
and this can be related to the electrochemical phenomenon that occurs at the steel–concrete interface. The present
studies, based on electrochemical impedance spectroscopy (EIS) conducted on three different densities of concrete
with addition of 0.5 and 1% chloride over a period of 1765 days, reveal that the capacitive behaviour of a lowfrequency
arc with a slope more than �1 indicates the passive condition of rebar. Warburg diffusion behaviour with
a slope exactly equal to �1 denotes the initiation of corrosion on the rebar. A slope of less than �1 is obtained
when corrosion spreads uniformly on the rebar. Other electrochemical parameters such as Rp, Cdl and phase angle
are correlated with the phenomenon occurring at the steel–concrete interface. An Rp value greater than 250 k�
cm2 indicates the passive condition of rebar, whereas values of less than 230 and 14 k� cm2 indicate initiation and
severe corrosion of the rebar respectively. Similarly, a Cdl value greater than 1000 �F/cm2 indicates the severe
corrosion of rebar, whereas less than 100 �F/cm2 denotes the passive condition of rebar. If the rebar is in the
passive condition, the phase angle is more than 308, whereas it is less than 208 under severe corrosion. The
reduction of intrinsic chloride diffusivity owing to pore restructuring by pozzolanic reaction and adsorption of a
greater amount of chloride ions into the interlayer of additional calcium silicate hydrate content are responsible for
delayed initiation of corrosion in Portland pozzolana cement (PPC) and Portland slag cement (PSC) concretes,
when compared with ordinary Portland cement (OPC) concrete
Electrochemical synthesis of nanosize polyaniline from aqueous surfactant solutions
No full textElectrochemical polymerization of aniline was carried out in micellar solutions of camphor sulphonic acid
(CSA, anionic surfactant), cetyltrimethylammonium bromide (CTAB, cationic surfactant) and TritonX 100
(Tx100, nonionic surfactant), to reveal the morphology against the nature of the surfactant molecule. The
resultant polyaniline film was characterized by Fourier transform infrared (FTIR) spectroscopic and cyclic
voltammetric techniques. The surface morphology observed from different surfactant molecules was found
to be distinctly different. Polyaniline synthesized from CSA and Tx100 solutions, showed uniform nanosized
(100 nm) globular structures
Effects of annealing temperature on structural, optical, and electrical properties of antimony-doped tin oxide thin films
No full textAntimony-doped tin oxide (ATO) films, approximately 320nm in thickness,
have been prepared by electron beam evaporation onto glass
substrates. The films were annealed at temperatures between 400C and 550C in air and their structure and surface morphologies were observed by
X-ray diffraction (XRD) and atomic force microscopy (AFM) after the
different annealing treatments. XRD patterns of the ATO thin films
as-deposited and annealed at 400�C showed that they were amorphous, but
annealing beyond 400�C caused the films to become polycrystalline with
tetragonal structure and orientated in the (1 1 0) direction. The grain size
in the annealed films, obtained from the XRD analysis, was in the range
146–256A ˚ and this increased with the annealing temperature. The
dislocation density, cell volume and strain were found to decrease gradually
with increasing annealing temperature. Photoluminescence spectra revealed
an intensive blue/violet peak at 420 nm, which increased gradually in height
with annealing. It is suggested that an increase in the population of Sbþ5
ions might be the reason for the enhancement of the blue/violet emission.
The optical properties of the films were also investigated in the
UV-visible-NIR region (300–1000 nm). The optical constants, namely
the refractive index n and the extinction coefficient k in the visible region
were calculated. The optical energy band gap, as determined by the
dependence of the absorption coefficient on the photon energy at short
wavelengths, was found to increase from 3.59 to 3.76 eV with annealing
temperature
Observation of Photoconductivity in Sn-Doped ZnO Nanowires and Their Photoenhanced Field Emission Behavior
No full textSn-doped ZnO nanowire films have been successfully synthesized by electrodeposition on zinc foil followed
by annealing in air at 400 °C for 4 h. The XRD patterns of the annealed specimens exhibit a set of welldefined
diffraction peaks indexed to the wurtzite phase of ZnO. The surface morphology of the as-synthesized films showed a network of densely packed flakes/sheets on the substrate. However, upon annealing, the formation of ZnO nanowires, processing length in the range of several micrometers and diameter less than 150 nm, on the entire substrate is observed. The relative atomic percentage of Sn, estimated from the energy dispersive spectra, was found to be 0.5 and 2.0 in the ZnO films deposited for 10 and 40 min durations,
respectively. From the field emission studies, the values of the turn-on field and threshold field, required to
draw emission current density of 10 and 100 μA/cm2, are observed to be 0.68 and 1.1 V/μm for 0.5% Sndoped
ZnO and 1.72 and 2.25 V/μm for 2.0% Sn-doped ZnO, respectively. The field emission current stability
investigated for a duration of 6 h at the preset value of 100 μA is found to be excellent. A prominent photoenhancement in the field emission current upon visible light illumination of the Sn-doped ZnO nanowires
films has been observed. This enhancement has been attributed to the photoconductivity of the Sn-doped
ZnO