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| Articles
by
Riaz Ahmed |
Total Records (
3 ) for
Riaz Ahmed |
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Muhammad ARSHAD
,
Saeed- ur-REHMAN
,
Ammad Hussain QURESHI
,
Khalid MASUD
,
Muhammad ARIF
,
Aamer SAEED
and
Riaz AHMED
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The nitrate complexes of transition metals with 1,2-diimidazoloethane
(DIE) of the general formula M(DIE)(NO3)2, where M = Co(II),
Cu(II), Zn(II), and Cd(II), were synthesized. The compositions of metal complexes
and ligand were investigated by elemental analysis in order to ensure their
purity and the structure elucidations were based on conductivity measurements,
room temperature magnetic moment studies, proton NMR, and electronic and IR
spectra. The thermal behavior of these complexes possessing distorted tetrahedral
geometry and their ligand was studied by means of thermoanalytical techniques
in static air atmosphere in order to determine their mode of decomposition and
thermal stability. All these complexes and ligand show 2-step weight loss upon
heating to 740 °C, with simultaneous loss of inorganic and organic fragments
exhibiting almost the same mode of decomposition pattern. The residue after
heating above 640 °C corresponded to metal oxide. There was no residue in the
case of ligand. The composition of intermediates and end products formed during
degradation was confirmed by microanalysis and IR spectroscopy. It follows from
the results that the thermal stability of the complexes increases in the following
sequence:
Co(II) < Cu(II) < Zn(II) < Cd(II) |
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Abdul Sattar Ali KHAN
,
Riaz AHMED
and
Muhammad Latif MIRZA
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The catalytic activities of an equal amount of 3 different
carbon supported catalysts containing 10% Pt, 20% Pt + 10% Ru, and
30% Pt were evaluated in neutral and basic media for methanol
oxidation by cyclic voltammetry. The prominent oxidation peak for
methanol appeared in the forward anodic sweep at around 1.0 V in
neutral medium, while in basic medium it appeared at significantly
lower potential close to 0.2 V. The peak current for methanol
oxidation was higher on a catalyst containing higher Pt loading. The
comparison of polarization behavior of 20% Pt + 10% Ru and 30% Pt
catalysts showed that the presence of Ru increases the catalytic
activity at the lower polarization region. The enhancement of
catalytic activity by Ru was more obvious in basic medium as compared
with neutral medium. The heterogeneous rate constants were evaluated
from peak current data. At room temperature, the heterogeneous rate
constant for methanol oxidation on a given catalyst was higher in
basic medium as compared with neutral medium. The effect of
temperature on peak current was investigated. At lower temperature,
the catalytic activities were lower in neutral medium but approached
near that in basic medium at higher temperature owing to the higher
apparent enthalpy of activation “Δ H*” for methanol oxidation
in neutral medium. The Δ H* values were calculated from the
analysis of peak current data and found to be in the range 24 to 27 kJ
mol-1 in neutral medium and 15 to 17 kJ mol-1 in basic medium. |
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Abdul Sattar Ali Khan
,
Riaz Ahmed
and
Muhammad Latif Mirza
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Platinum-based catalysts are considered the most efficient
catalysts for triggering electrochemical reactions in proton exchange
membrane (PEM) fuel cells. In the present study, commercial catalysts
containing 10% and 30% Pt supported on Vulcan XC-72 carbon were
studied to assess their performance in PEM fuel cells. Both catalysts
consisted of Pt particles of almost the same size. The utility of
these catalysts in PEM fuel cells was studied by finding the real
surface area and rate of electro-oxidation of methanol in 0.5 M
H2SO4 by using cyclic voltammetry. The methanol oxidation reaction
was used for characterization of catalysts of PEM fuel cells due to
the liquid nature of methanol and the close resemblance of basic
electrochemical features of direct methanol fuel cells and PEM fuel
cells. Comparison of the data of real surface area and rate of
electro-oxidation of methanol showed that 30% Pt catalyst having
higher Pt loading is more suitable for PEM fuel cells as compared with
10% Pt catalyst. The PEM fuel cell components were designed and
fabricated for testing of membrane electrode assemblies (MEAs). The
importance of an additional gas diffusion layer in the form of carbon
paper was also emphasized for improving gas diffusion and electrical
contact of electrodes of MEAs with the flow field area of
monopolar/bipolar plates of PEM fuel cells. The MEAs prepared from
10% and 30% Pt catalysts with Pt loading of 0.5 mg cm-2 gave
the maximum power density of 119 and 185 mW cm-2, respectively. It
was concluded that nanosize carbon supported Pt catalysts having
higher Pt loading are more suitable catalysts for preparing high
performance MEAs of PEM fuel cells and the cyclic voltammetric data of
real surface area and rate of methanol oxidation may be utilized to
assess the performance of a given catalyst prior to its use in the
preparation of MEAs of PEM fuel cells. |
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