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Pigment–Acceptor–Catalyst Triads for Photochemical Hydrogen Evolution

Authors

  • Kyoji Kitamoto,

    1. Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581 (Japan)
    2. International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University (Japan)
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  • Prof. Ken Sakai

    Corresponding author
    1. Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581 (Japan)
    2. International Institute for Carbon-Neutral Energy Research (WPI-I2CNER), Kyushu University (Japan)
    3. Center for Molecular Systems (CMS), Kyushu University (Japan)
    • Department of Chemistry, Faculty of Sciences, Kyushu University, Hakozaki 6-10-1, Higashi-ku, Fukuoka, 812-8581 (Japan)===

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  • This work was partly supported by a Grant-in-Aid for Scientific Research (B) (grant no. 24350029), a Grant-in-Aid for Scientific Research on Innovative Areas “Coordination Programming” (No. 2107) (grant no. 24108732), and a Grant-in-Aid for Scientific Research on Innovative Areas “Artificial Photosynthesis” (No. 2406) (grant no. 24107004) from the Ministry of Education, Culture, Sports, Science, and Technology (MEXT) of Japan. This was further supported by the International Institute for Carbon Neutral Energy Research (WPI-I2CNER), sponsored by the World Premier International Research Center Initiative (WPI), MEXT (Japan). K.K. acknowledges Research Fellowships of the Japan Society for the Promotion of Science for Young Scientists.

Abstract

In order to solve the problems of global warming and shortage of fossil fuels, researchers have been endeavoring to achieve artificial photosynthesis: splitting water into H2 and O2 under solar light illumination. Our group has recently invented a unique system that drives photoinduced water reduction through “Z-scheme” photosynthetic pathways. Nevertheless, that system still suffered from a low turnover number (TON) of the photocatalytic cycle (TON=4.1). We have now found and describe herein a new methodology to make significant improvements in the TON, up to around TON=14–27. For the new model systems reported herein, the quantum efficiency of the second photoinduced step in the Z-scheme photosynthesis is dramatically improved by introducing multiviologen tethers to temporarily collect the high-energy electron generated in the first photoinduced step. These are unique examples of “pigment–acceptor–catalyst triads”, which demonstrate a new effective type of artificial photosynthesis.

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