Research Institute for Technical Physics and Materials Science of HAS

Budapest, Hungary

Research Institute for Technical Physics and Materials Science of HAS

Budapest, Hungary
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Horvath A.,Institute of Isotope and Surface Chemistry of Hungary | Stefler G.,Institute of Isotope and Surface Chemistry of Hungary | Geszti O.,Research Institute for Technical Physics and Materials Science of HAS | Kienneman A.,CNRS The Institute of Chemistry and Processes for Energy, Environment and Health | And 3 more authors.
Catalysis Today | Year: 2011

Ni, NiRh and NiCo catalysts supported on Ce-Zr-oxide synthesised by pseudo sol-gel method have been investigated. Monometallic samples were performed with two different Ce/Zr ratios and by conventional impregnation. BET, XPS, TPR, TPO and TEM were applied for sample characterization and dry reforming of methane was carried out with a feed mixture consisted of CH4/CO 2/Ar = 10/10/80 or CH4/CO2 = 70/30 ratio. Co and Rh containing samples were proved to be stable catalysts, the impregnated Ni catalyst only slightly, while sol-gel Ni samples slowly deactivated during the long term overnight run. The amount of carbon on the sample's surface after catalytic runs varied between 1 and 12 mg C/100 mg of catalyst. The Ni samples prepared by sol-gel and impregnation method had a peak maximum in TPO at 400 °C and 600 °C, respectively. In the case of bimetallic sol-gel samples the carbon that gave TPO peak at 360 °C was slowly transformed to that at 600 °C, showing that after several carbon deposition (dry reforming) and gasification (TPO) cycles structural changes in the catalyst and in the carbon morphology take place and graphitic carbon and nanotube formation become prevailing as was detected by TEM. Upon high temperature pre-treatment and methane dry reforming reaction, alloyed NiRh, NiCo particles and sintered Ni were observed, with the simultaneous presence of carbidic carbon, carbon nanotubes and shell-type graphitic carbon deposition. Support degradation and segregation happened to some extent, but still there was a certain amount of Ni in strong interaction with the support probably still included in the oxide matrix. Broad metal particle size distribution seems to play a role in long term stability. When pure methane was decomposed on Ni catalyst prepared by sol-gel method, the carbonaceous deposit could completely be removed by the subsequent CO2 treatment, emphasizing the active role of Ce-Zr mixed oxide support in gasification of surface coke.


Galkin N.G.,RAS Institute of Radio Engineering and Electronics | Dozsa L.,Research Institute for Technical Physics and Materials Science of HAS | Chusovitin E.A.,RAS Institute of Radio Engineering and Electronics | Dotsenko S.A.,RAS Institute of Radio Engineering and Electronics | And 2 more authors.
Physics Procedia | Year: 2011

Semiconducting CrSi2 nanocrystals (NCs) with high density (4×1010 cm-2) and narrow size distribution were grown by reactive deposition epitaxy (RDE) of 0.6 nm Cr at 550 °C on Si(111)7×7 substrate. Based on DRS, AFM and TEM results silicon cap epitaxy growth procedure on silicon with high density of CrSi2 NCs has been proposed. Monolithic Si(111)/CrSi2 NCs/Si(111) structures with three layers of buried CrSi2 NCs have been successfully grown by repeating of CrSi2 NCs formation and silicon epitaxial growth. Electrical characterization of Schottky junctions formed on the grown structures has shown that the formation of point defects generated during the growth of the Si cap layer strongly depends on the cap growth conditions and on the Cr deposition rate. © 2010 Published by Elsevier B.V.


Horvath A.,Institute of Isotope and Surface Chemistry of Hungary | Beck A.,Institute of Isotope and Surface Chemistry of Hungary | Stefler G.,Institute of Isotope and Surface Chemistry of Hungary | Benko T.,Institute of Isotope and Surface Chemistry of Hungary | And 4 more authors.
Journal of Physical Chemistry C | Year: 2011

SiO2-supported Au nanoparticles derived from sol were promoted with 0.04-7.4 wt % CeO2 using two methods. The addition of Ce precursor was done directly to the Au sols before sol immobilization step (method A) or to the suspension of parent Au/SiO2 (method B). Both preparation routes resulted in CeO2 decoration of 1-3 nm over Au nanoparticles, which induced high CO oxidation activity. However, above 0.6 wt % CeO2 content, the activity did not change significantly, but it greatly exceeded that of pure Au/CeO2 used for reference. High-resolution transmission microscopy (HRTEM) showed that up to this concentration ceria patches are attached onto gold surface, and the further increase in Ce-loading caused CeO2 spread over the support surface as well. Strong interaction of Ce species with stabilizer ligands located around Au is suggested as the reason for CeO2 localization on gold. © 2011 American Chemical Society.

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