Accumulation Process of Photogenerated Electrons in Titanium(IV) Oxide Photocatalyst Particles: Photoacoustic Infrared Spectroscopy Study

• Published in: Journal of physical chemistry. C Vol. 126; no. 10; pp. 4889 - 4898
• Main Authors: Shinoda, Tatsuki, Murakami, Naoya
• Format: Journal Article
• Language: English
• Published: American Chemical Society 17.03.2022
• Subjects: C: Chemical and Catalytic Reactivity at Interfaces; crystal structure; energy; infrared spectroscopy; irradiation; photocatalysts; surface area; titanium; ultraviolet radiation
• ISSN: 1932-7447; 1932-7455; 1932-7455
• DOI: 10.1021/acs.jpcc.2c00603

Photoabsorption of trapped electrons in titanium­(IV) oxide (TiO2) particles was investigated by using photoacoustic infrared spectroscopy (IR-PAS). During ultraviolet (UV) irradiation, an upward shift of the IR-PAS spectrum appeared as a result of increment of the photoacoustic (PA) signal due to accumulation of trapped electrons at defective sites in TiO2 particles. The results for various samples indicated that anatase TiO2 (specific surface area (SSA): 11–290 m2 g–1) possesses shallower energy trapping sites for electrons than rutile (SSA: 27–114 m2 g–1) and brookite TiO2 (SSA: 23 m2 g–1). Time-course IR-PAS measurements also suggested that the accumulation process of photogenerated electrons in TiO2 particles during steady-state UV irradiation depends on the energy depth of electron trapping sites and that the behavior of photogenerated electrons is mainly determined by the crystal structure. Thus, the IR-PAS method is a useful technique for analysis of the generation process and energy depth of trapped electrons in powdered photocatalysts during steady-state excited-light irradiation.