Catalytic role of bridging oxygens in TiO2 liquid phase photocatalytic reactions
Analysis of H216O photooxidation on labeled Ti18O2
- authored by
- J.F. Montoya, D.W. Bahnemann, P. Salvador, J. Peral
- Abstract
Experiments of photocatalytic oxidation of H
2
16O with a suspended oxygen-isotope labelled Ti
18O
2 photocatalyst are presented here for the first time. The photo-induced evolution of
18O
16O demonstrates that bridging surface oxygens (>
18O
br
2-) behave as real catalytic species of the global water splitting photocatalytic reaction (2H
2O + 4h
+ → O
2(g)↑ + 4H
+). The experimental results are interpreted according to a previously developed water redox photooxidation (WRP) mechanism (Salvador, P. Prog. Surf. Sci. 2011, 86, 41-58), opening a new mechanistic pathway that involves the participation of terminal >O
br
2- bridging oxygens as real photocatalytic species. In the primary step, one-fold coordinated -
18O
br
- radicals are generated from the direct photooxidation of >
18O
br
2- oxygens with valence band holes (>
18O
br
2- + h
+ → -
18O
br
-). In the second step, a couple of adjacent -
18O
br
- radicals chemically react, giving rise to peroxo species (2
18O
br
- →
18O
2
2-), which are further photooxidized with photogenerated valence band holes, initially leading to
18O
2(g) evolution according to the global photoreaction
18O
2
2- + 4h
+ → 2V[>
18O
br
2-] +
18O
2(g)↑. Terminal oxygen vacancies (V[>
18O
br
2-]) become further healed via dissociative adsorption of H
2
16O water molecules (2V[>
18O
br
2-] + 2H
2
16O → 2(>
16O
br
2-) + 2H
+), in such a way that >
18O
br
2- bridging ions are progressively substituted by >
16O
br
2- and the initially evolved
18O
2(g) is further replaced by
16,18O
2(g) and finally by
16O
2(g).
- Organisation(s)
-
Institute of Technical Chemistry
- Type
- Article
- Journal
- Catalysis Science and Technology
- Volume
- 7
- Pages
- 902-910
- No. of pages
- 9
- ISSN
- 2044-4753
- Publication date
- 21.02.2017
- Publication status
- Published
- Peer reviewed
- Yes
- ASJC Scopus subject areas
- Catalysis
- Sustainable Development Goals
- SDG 7 - Affordable and Clean Energy
- Electronic version(s)
-
https://doi.org/10.1039/c6cy02457b (Access:
Closed)
