A simple and effective strategy is presented to integrate individual platinum nanoparticles (NPs) into macroscopic thin films based on the reduction of organoplatinum(II) complexes [PtCl2(cod)] 1a, [PtI2(cod)] 1b (cod = 1,5-cyclooctadiene) and cis-[Pt(p-MeC6H4)2(SMe2)2] 2, at the toluene-water interface in the absence of stabilizer. Structure and morphology of the platinum NPs were characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and selected area electron diffraction (SAED) techniques. Finally, platinum thin films were deposited on glassy carbon electrode and their electro-oxidation was investigated in the methanol oxidation reaction. Pt NPs thin films showed highly improved electrocatalytical activity toward methanol oxidation as compared with commercial platinum catalysts. The present method provides a facile and low-cost strategy toward the synthesis of different electrocatalysts of noble metals for application in fuel cells.
Asphaltene
deposition is one of the most challenging aspects of
the petroleum industry that takes place through production, processing,
and transportation. In the present study, first, the effect of temperature
on the aggregation kinetics of asphaltene in a heptane–toluene
mixture is investigated during a set of experiments done at different
fixed temperatures. In spite of most previous works in which the collision
efficiency is assumed to be constant and equal to one, the obtained
experimental data in this study provides deep insights into the mechanism
of aggregation of asphaltene particles within an organic medium. A
population balance model considering the fractal structure for asphaltene
aggregates and variable value for collision efficiency is developed
to predict the enlargement of asphaltene floccules with the passage
of time. The results show that the assumption of a constant value
for collision efficiency is not realistic. The calculated value of
collision efficiency decreases with the increase of average particle
size during each experiment. Also, the value of collision efficiency
decreases with the increase of temperature. In the second part of
this work, the zeta potential of asphaltene aggregates in the mixture
is measured during the evolution of floccules in separate tests. These
results are applied to investigate the asphaltene stability and also
to validate the size measurement data obtained in the first part.
The measured zeta potentials of evolving particles indicate that the
asphaltene aggregates are more stable at high temperatures than at
low temperatures. Due to this fact, aggregates reach a significantly
smaller mean size at high temperatures in comparison to that at low
temperatures.
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