Reactions of radicals at nanoparticles surfaces

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Tomer Zidki

Ariel University, Israel

: J Nanomater Mol Nanotechnol

Abstract

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Radicals reactions are of importance due to their formation near surfaces in a variety of processes, e.g. in catalytic processes, in electrochemistry, in photo-catalytic processes, in environmental processes, etc. It was therefore decided to study the mechanisms and kinetics of reaction of M°-NPs, M=Ag; Au; Cu; Pt; Pd, Pt/Au-alloy-NPs and TiO2-NPs with methyl radicals. (All the M°-NPs were prepared by reduction of the corresponding salts with NaBH4). These reactions are very fast, approaching the diffusion-controlled limit, forming long-lived transients with (M°-NP)-(CH3)n σ bonds. These transients decompose yielding C2H6 for Ag°-, Au°- and TiO2-NPs, CH4 for Cu°-NPs, for Pt°- and Pd°-NPs most methyl remain bound to the NPs, and are released as methane when H2 is added to the suspension, though some C2H6, C2H4 and oligomerization products are formed. The reaction of .C(CH3)2OH radicals with SiO2 supported metal-NPs (M°-SiO2-NCs, NCs=nanocomposites) is more complicated. At low [M°-SiO2-NCs], the NCs catalyze the reduction of water by these radicals, for M=Pt the NCs are clearly a catalyst while the Pt°-NPs are not; For M=Ag the NCs catalyze the reduction of water but considerably less than the Ag°-NPs; for M=Au both the MPs and the NCs catalyze the reduction of water. At high [M°-SiO2-NCs] the reduction of water is considerably decreased and at high doses of radicals the Pt°- and Ag°-NCs do not catalyze the reduction of water by the .C(CH3)2OH radicals and induce their disproportionation, and their reduction by H2, on the NCs surfaces. Thus, the SiO2 support affects considerably the properties of the M°-NPs and the nature of this effect depends on the nature of the M°-NPs.

Biography

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Tomer Zidki has completed his PhD in 2009 at Ben-Gurion University of the Negev and has his expertise in “Mechanistic studies of catalytic reactions at nanoparticles surfaces”. His studies show that radicals react extremely fast with metal and supported metal nanoparticles. The products of these reactions are long-lived metalcarbon intermediates in which their lifetime depends on the metal nature. He also has interest in “Catalytic water splitting reactions” and developed very efficient water oxidation catalysts based on co-hydrous-oxide nanoparticles supported on SiO2 nanoparticles. Recently, he developed new metal-alloys nanoparticles which show superior catalytic activity as well as TiO2 based nanocomposites which will be used for various catalytic and photocatalytic reactions.

Email: tomerzi@ariel.ac.il