Coating Platinum Nanoparticles with Methyl Radicals: Effects on Properties and Catalytic Implications

Ronen Bar-Ziv, Israel Zilbermann, Michael Shandalov, Vladimir Shevchenko, Dan Meyerstein

Research output: Contribution to journalArticlepeer-review

14 Scopus citations

Abstract

It was recently reported that the reaction of methyl radicals with Pt0 nanoparticles (NPs), prepared by the reduction of Pt(SO4)2 with NaBH4, is fast and yields as the major product stable (Pt0-NPs)- (CH3)n and as side products, in low yields, C2H6, C2H4, and some oligomers. We decided to study the effect of this coating on the properties of the Pt0-NPs. The results show that the coating can cover up to 75 % of the surface Pt0 atoms. The rate constant of the reaction, k(.CH3+Pt0-NPs), decreases with the increase in the surface coverage, leading to competing reaction paths in the solution, which gradually become dominant, affecting the composition of the products. The methyl coating also affects the zeta potential, the UV spectra, and the electrocatalytic reduction of water in the presence of the NPs. Thus, the results suggest that binding alkyl radicals to Pt0 surfaces might poison the NPs catalytic activity. When the Pt0-NPs are prepared by the reduction of a different precursor salt, PtCl62-, nearly no C2H4 and oligomers are formed and the methyl coating covers a larger percentage of the surface Pt0 atoms. The difference is attributed to the morphology of the Pt0-NPs: those prepared from Pt(SO4)2 are twinned nanocrystals, whereas those prepared from PtCl62- consist mostly of single crystals. Thus, the results indicate that the side products, or most of them at least, are formed on the twinned Pt0 nanocrystal edges created between (111) facets. In addition, the results show that Pt0-NPs react very differently compared with other noble metals, for example, Au0 and Ag0; this difference is attributed in part to the difference in the bond strength, (M0-NP)- CH3, and should be considered in heterogeneous catalytic processes involving alkyl radicals as intermediates.

Original languageEnglish
Pages (from-to)19000-19009
Number of pages10
JournalChemistry - A European Journal
Volume21
Issue number52
DOIs
StatePublished - 21 Dec 2015

Keywords

  • heterogeneous catalysis
  • methyl radicals
  • nanoparticles
  • platinum
  • reaction mechanisms

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