A detailed study of the structure, morphology and electrochemical properties of Pt/C and Pt/x-SnO2/C catalysts synthesized using a polyol method has been provided. A series of catalysts supported on the SnO2-modified carbon was synthesized and studied by various methods including transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), electrochemical methods, and fuel cell testing. The SnO2 content varies from 5 to 40 wt %. The TEM images, XRD and XPS analysis suggested the Pt-SnO2 hetero-clusters formation. The SnO2 content of ca. 10% ensures an optimal catalytic layer structure and morphology providing uniform distribution of Pt-SnO2 clusters over the carbon support surface. Pt/10wt %-SnO2/C catalyst demonstrates increased activity and durability toward the oxygen reduction reaction (ORR) in course of accelerated stress testing due to the high stability of SnO2 and its interaction with Pt. The polymer electrolyte membrane fuel cell current–voltage performance of the Pt/10wt %-SnO2/C is comparable with those of Pt/C, however, higher durability is expected.
Reduced graphene oxide (RGO) and RGO modified by ozone (RGO-O) and fluorine (RGO-F) were synthesized. Pt nanoparticles were deposited on these materials and also on Vulcan XC-72 using the polyol method. The structural and electrochemical properties of the obtained catalysts were investigated in a model glass three-electrode electrochemical cell and in a laboratory PEM fuel cell. Among the RGO-based catalysts, the highest electrochemically active surface area (EASA) was obtained for the oxidized RGO supported catalyst. The EASA of the fluorine-modified RGO-supported catalyst was half as big. In the PEM fuel cell the performance of RGO-based catalysts did not exceed the activity of Vulcan XC-72-based catalysts. However, the addition of an RGO-O-based catalyst to Vulcan XC-72-based catalyst (in contrast to the RGO-F-based catalyst) allowed us to increase the catalyst layer activity and PEM fuel cell performance. Possible reasons for such an effect are discussed.
We
report on a technique of femtosecond laser-induced crystallization
of glass, allowing improvement in the homogeneity of continuous crystalline
tracks formed in lanthanum borogermanate glass using a focused beam
with the elliptical-shaped waist cross section instead of a conventional
circular one. Second harmonic generation produced by near-infrared
femtosecond laser pulses was demonstrated in the waveguiding mode
for the laser written crystalline track. The structure of the fabricated
single crystalline waveguides is investigated with high resolution
transmission electron microscopy and micro-Raman spectroscopy.
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