Effect of Ti3+ Ions and Conduction Band Electrons on Photocatalytic and Photoelectrochemical Activity of Rutile Titania for Water Oxidation

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• 作者：Fumiaki Amano ; Masashi Nakata ; Akira Yamamoto ; Tsunehiro Tanaka
• 刊名：Journal of Physical Chemistry C
• 出版年：2016
• 出版时间：March 31, 2016
• 年：2016
• 卷：120
• 期：12
• 页码：6467-6474
• 全文大小：498K
• ISSN：1932-7455

文摘

Although TiO₂ is generally considered to be an oxygen deficient n-type compound, the role of oxygen vacancies and Ti³⁺ ions on its photocatalytic activity is not fully understood. In this study, we investigated the effects of high-temperature calcination and H₂ reduction treatment on the water oxidation activity of rutile TiO₂ under ultraviolet irradiation. Calcination above 900 °C decreased the photocatalytic activity of the TiO₂ owing to strong oxidation, but its initial activity was restored by H₂ treatment at above 500 °C. Electron spin resonance (ESR) spectra showed that the high-temperature calcination created O^•– radicals (trapped hole in oxygen lattice site), while the H₂ reduction treatment created Ti³⁺ ions (trapped electron in titanium lattice site) with oxygen vacancies. Diffuse reflectance ultraviolet–visible–near-infrared (UV–vis–NIR) spectroscopy indicated an increase in the amount of electrons in shallow traps and the conduction band with H₂ treatment temperature. Measurements of the sheet resistance and space charge layer capacitance of the thermally oxidized TiO₂ films indicated that the H₂ treatment improved the electrical conductivity owing to an increase in donor density (electron density). Thus, the increase in the photocatalytic and photoelectrochemical activities of the rutile TiO₂ was attributed to donor doping by H₂ reduction.