Nakabayashi Yukihiro, Nosaka Yoshio
Department of Materials Science and Technology, Nagaoka University of Technology, Nagaoka, 940-2188 Japan.
Phys Chem Chem Phys. 2015 Nov 11;17(45):30570-6. doi: 10.1039/c5cp04531b.
It has been believed that photocatalytic oxidation in water proceeds with the reaction of OH radicals generated on the photocatalysts. To explore the actual contribution of OH radicals to photocatalytic oxidation, OH radicals were detected by fluorescence probe method in photoelectrolysis with rutile TiO2 of (100) and (110) facets. The effect of hydrogen peroxide on the OH radical formation at pH 6.7 was investigated to confirm the relevant intermediate which was suggested in our previous report for water oxidation. In alkaline solutions at pH 9.6 and 12.5, the current efficiencies of OH radical formation were 0.01-0.05%, which are far smaller than those at pH 6.7 (0.2-0.6%) due to the deprotonation of the reaction intermediate as confirmed by FT-IR measurements. These experimental results support a plausible reaction mechanism that the surface Ti-O-O-Ti structure is an intermediate of the water oxidation process, by which mechanism the O2 production becomes favorable in alkaline solution.
人们一直认为，水中的光催化氧化是通过光催化剂上产生的羟基自由基的反应进行的。为了探究羟基自由基对光催化氧化的实际贡献，采用荧光探针法在（100）和（110）面的金红石TiO₂光电解中检测羟基自由基。研究了过氧化氢对pH 6.7时羟基自由基形成的影响，以确认我们之前关于水氧化的报告中提出的相关中间体。在pH 9.6和12.5的碱性溶液中，羟基自由基形成的电流效率为0.01 - 0.05%，远低于pH 6.7时的电流效率（0.2 - 0.6%），这是由于FT-IR测量证实反应中间体发生了去质子化。这些实验结果支持了一种合理的反应机制，即表面Ti-O-O-Ti结构是水氧化过程的中间体，通过该机制，在碱性溶液中产生氧气变得有利。
