Long-Lived Photocatalysis Centers Created in ZnO via Resonant Exciton Excitation
ZnO together with TiO2 is a main photocatalyst for various redox reactions to convert light energy into a chemical one and to purify the environment. Intrinsic surface defects in ZnO—the vacancies in anionic and cationic sublattices (F-type and V-type centers)—allow creation of long-lived (up to 103 s) photocatalysis centers and, therefore, tenfold increase in quantum yield of reactions. Slow surface states—the photocatalysis centers—appear via diffusion of electrons and holes generated during the interband transitions in the bulk of a photoactivated sample. The transfer efficiency, however, decreases sharply because of recombination of charge carriers and losses during overcoming the surface Schottky barrier. Neutral energy carriers—excitons—were used in this work to decrease these losses during the energy transfer to a surface. High exciton binding energy in ZnO (60 meV) allows it to move at room temperature without decay. The exciton energy loss for radiation is effectively decreased in our experiments via formation of a 2D surface structure. The results confirm high efficiency of exciton channel to form surface long-lived photocatalysis F-centers and V‑centers during the photoadsorption and photodesorption processes of oxygen, which simulate full cycle of a redox photocatalytic reaction.
Keywords:ZnO excitons oxygen photoadsorption photodesorption surface long-lived centers 2D structure
The authors are grateful to the staff of St. Petersburg State University Resource Centers: “Nanocomposites,” “Physical Methods of Surface Research,” “X-ray Diffraction Studies,” and “Nanophotonics.”
This work was financially supported by the Russian Foundation for Basic Research (project no. 18-03-00754).
CONFLICT OF INTEREST
The authors declare that they have no conflicts of interest.
- 3.C. Jagadish and S. Pearton, Zinc Oxide: Bulk, Thin Films and Nanostructures (Elsevier, Amsterdam, 2006).Google Scholar
- 9.I. Kh. Akopyan, M. E. Labzovskaya, A. A. Lisachenko, B. V. Novikov, A. Yu. Serov, V. V. Titov, N. G. Filosofov, Phys. Solid State 58, No. 9, 1767 (2016).Google Scholar
- 11.A. A. Lisachenko, Phys. Low-Dim. Struct., Nos. 7–8, 1 (2000).Google Scholar