Unusual Reduction of Graphene Oxide by Titanium Dioxide Electrons Produced by Ionizing Radiation: Reaction Products and Mechanism

David Behar, Tijana Rajh, Yuzi Liu, Justin Connell, Vojislav Stamenkovic, Joseph Rabani

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

The research concerns the reduction of graphene oxide (GO) by excess electrons on TiO2 nanocrystallites, eTiO2 -, produced with the aid of ionizing radiation in the presence of 2-propanol at acidic pH prior to mixing with a GO solution. Under these conditions, 2-propanol reacts with the radiation-produced â¢OH radicals and produces the strongly reducing CH3Câ¢OHCH3 free radicals. The latter, together with the radiation-produced hydrated electrons, reacts with the TiO2 nanoparticles by electron transfer, producing up to 60 excess electrons per colloid particle. The reaction of eTiO2 - with GO takes place after mixing the two sols. The reaction kinetics shows a multistage reduction, extending from seconds to many minutes. Simulations of the time profile of eTiO2 - based on the complex kinetics involving four types of reactive GO segments reacting with eTiO2 - agree with the observed rate of electron decay. The multireaction kinetics is expected in view of several reducible segments of GO (Câ•C, C-O-C, C-OH, and Câ•O) and the trapping energy distribution of eTiO2 -. GO used in the present study had 48.8% Câ•C (sp2), 3.4% C-C (sp3), 29.6% C-O bonds (as C-OH and C-O-C), 12.6% Câ•O, and 5.6% O-Câ•O. XPS analysis along the reaction time shows that the reduction of the oxygen-containing segments is the fastest process, while the saturation of Câ•C double bonds is considerably slower. The latter involves the formation of C-H and C-C bonds. High-resolution transmission electron microscopy (HRTEM) shows the formation of nanodiamond islands within the amorphous carbon backbone.

Original languageEnglish (US)
Pages (from-to)5425-5435
Number of pages11
JournalJournal of Physical Chemistry C
Volume124
Issue number9
DOIs
StatePublished - Mar 5 2020
Externally publishedYes

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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