Time-resolved rapid-scan FTIR was used to detect the surface intermediate in the water oxidation over Co3O4 nanoparticle catalyst. Two transient infrared bands (species B1013 cm-1 and speciesA840 cm-1) attributed to different surface reaction intermediates were observed in aqueous solution at pH 8.5. Species B1013 cm-1 has isotopic counterparts at 995 and 966 cm-1 in H218O, and at 975 cm-1 in D2O (figure a). Therefore, B1013 cm-1 is proposed to possess a Co(III)OO group with superoxide electronic structure which is hydrogen bonded to an adjacent CoOH (CoOD) or possibly another hydroxyl group such as a protonated bridging oxygen. The isotopic composition of the product in H218O (analyzed with mass spectrometry) agrees well with that in the superoxide species B, which proves that species B is the direct intermediate for the product oxygen. No significant 18O or D isotope frequency shifts was observed for species A840 cm-1 when using H218O or D2O (figure b). The very different kinetic behavior of species B1013 cm-1 and A840 cm-1 indicates that they originate from different surface species (figure c). We propose assignment of the 840 cm-1 band to a surface Co(IV)=O site, formed by oxidation of a surface Co(III)-OH group upon transfer of a hole from [Ru(bpy)3]3+ to Co3O4under concurrent loss of a proton.Figure  ?1 ?: (a) The absorption of species B in H216O (a), H218O (b), D2O (c) and control (without Co3O-4) in H216O (d). (b) The absorption of species A in H216O, H218O, D2O and in control (without Co3O4) in H216O. (c) The kinetics of species B, Ru(bpy)33+ (upper) and species A in H216O (bottom).References [1] M. Zhang, M. de Respinis, H. Frei Nat. Chem. DOI: 10.1038/NCHEM.1874, 2014  .

Direct observations of water oxidation intermediates on Co<sub>3</sub>O<sub>4</sub> nanoparticle catalysts with time-resolved FTIR spectroscopy

248th National Meeting (2014)

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.

Direct observations of water oxidation intermediates on Co3O4 nanoparticle catalysts with time-resolved FTIR spectroscopy

Direct observations of water oxidation intermediates on Co₃O₄ nanoparticle catalysts with time-resolved FTIR spectroscopy