Factors affecting oxygen evolution through water oxidation on polycrystalline titanium dioxide

• Published in: RSC advances Vol. 6; no. 52; pp. 46994 - 47000
• Main Authors: Nishimoto, Yuuya, Hasegawa, Yuichi, Adachi, Kenta, Yamazaki, Suzuko
• Format: Journal Article
• Language: English
• Published: 01.01.2016
• Subjects: Catalytic activity; Crystallites; Evolution; Oxidation; Photocatalysis; Reduction; Specific surface; Titanium dioxide
• ISSN: 2046-2069; 2046-2069
• DOI: 10.1039/C6RA06151F

The effect of physicochemical properties such as specific surface area, crystalline phase, crystallite size, and crystallinity of TiO 2 on photocatalytic water oxidation was investigated. Two types of polycrystalline TiO 2 samples which have different physicochemical properties were prepared by a sol–gel method. The photocatalytic activities of the TiO 2 samples for water oxidation were evaluated by the O 2 evolution rate from an aqueous silver nitrate solution under ultraviolet light irradiation. Comparison of the two types of TiO 2 samples revealed that the specific surface area and crystalline phase were not related to the O 2 evolution rate. In contrast, a linear relationship between the crystallite sizes and the O 2 evolution rates was observed for most of the TiO 2 samples. Crystal face selective Pt and PbO 2 depositions on the TiO 2 samples were observed by photocatalytic reduction of PtCl 6 2− and oxidation of Pb 2+ ions, respectively, indicating that the oxidation and reduction sites are separated on the surface. An increase in the crystallite size of the TiO 2 promotes a spatial separation of the redox sites and suppresses the electron–hole recombination, leading to the enhancement of the photocatalytic activity.