Biography
Biography: Tomer Zidki
Abstract
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.