Trapped State Sensitive Kinetics in LaTiO2N Solid Photocatalyst with and without Cocatalyst Loading

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• 作者：Rupashree Balia Singh ; Hiroyuki Matsuzaki ; Yohichi Suzuki ; Kazuhiko Seki ; Tsutomu Minegishi ; Takashi Hisatomi ; Kazunari Domen ; Akihiro Furube
• 刊名：Journal of the American Chemical Society
• 出版年：2014
• 出版时间：December 10, 2014
• 年：2014
• 卷：136
• 期：49
• 页码：17324-17331
• 全文大小：440K
• ISSN：1520-5126

文摘

In addition to the process of photogeneration of electrons and holes in photocatalyst materials, the competitive process of trapping of these charge carriers by existing defects, which can both enhance the photocatalytic activity by promoting electron鈥揾ole separation or can deteriorate the activity by serving as recombination centers, is also very crucial to the overall performance of the photocatalyst. In this work, using femtosecond diffuse reflectance spectroscopy we have provided evidence for the existence of energetically distributed trapped states in visible-light responsive solid photocatalyst powder material LaTiO₂N (LTON). We observe trapped state sensitive kinetics in bare-LTON. CoO_x cocatalyst loading (2 wt % CoO_x-LTON) shows effect on the kinetics only when presence of excess energy (for above bandgap excitation) results in the generation of surface carriers. Thus, the kinetics show appreciable excitation wavelength dependence, and the experimental results obtained for different 位_exc have been rationalized on this basis. In an earlier work by Domen and co-workers, the optimized CoO_x/LTON has been reported to exhibit a high quantum efficiency of 27.1 卤 2.6% at 440 nm, the highest reported for this class of photocatalysts (J. Am. Chem. Soc. 2012, 134, 8348鈥?351). In the present work, the mechanism is addressed in terms of picosecond charge carrier dynamics.