Dominant role of OH and Ti defects on the electronic structure of TiO thin films for water splitting

Anatase/rutile constituting TiO 2 thin films were prepared by sputter deposition, and the influence of the post-annealing step with a narrow window at 200 °C revealed a gaining factor of 5 in H 2 production. An in-depth analysis of the photocatalytic performance revealed the dominant role of interme...

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Published in:Dalton transactions : an international journal of inorganic chemistry 2022-10, Vol.51 (4), p.153-15311
Main Authors: Mendoza Diaz, Maria Isabel, Balocchi, Andrea, Oyekan, Kolade, Tan, Kui, Vandenberghe, William G, Esteve, Alain, Rossi, Carole
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Summary:Anatase/rutile constituting TiO 2 thin films were prepared by sputter deposition, and the influence of the post-annealing step with a narrow window at 200 °C revealed a gaining factor of 5 in H 2 production. An in-depth analysis of the photocatalytic performance revealed the dominant role of intermediate states rather than the heterocrystalline nature and the mesoscale structure. Structural, chemical and optical investigations based on scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, UV-visible spectroscopy and photoluminescence supported by ab initio calculation correlated the H 2 production with the dual presence of OH − and Ti 3+ defects in the form of titanium interstitial atoms. In addition, steady-state photoluminescence measurements determined the chemically active role of ethanol, commonly used as a hole scavenger, in inducing deep hole traps upon dissociation on the surface. These results give new directions for the design of TiO 2 based photocatalytic systems for light-driven H 2 production through water splitting, guided by a detailed description of defects present on the electronic structure and their chemical identification. Electron traps are created by Ti 3+ species associated to Ti interstitials and oxygen vacancies, whereas hole traps are associated to adsorbed OH − ; thus, extending the charges lifetime contributing to the redox reactions for H 2 production.
ISSN:1477-9226
1477-9234
DOI:10.1039/d2dt01871c