This chapter focuses on photocatalytic mechanisms of hydrogen (H2) evolution to clarify how photons are converted to two electrons that are required for H2 production from two protons. A two-electron-reduced metal complex is produced via disproportionation of the one-electron-reduced species of a metal complex produced via photoinduced electron transfer, leading to H2 evolution. A one-photon two-electron process is made possible in photocatalytic H2 evolution by combination of thermal and photoinduced electron transfer. Photoexcitation of 9-mesityl-10-methylacridinium ion (Acr+–Mes) with NADH that is a hydride (two-electrons and a proton) donor resulted in the reduction of two equivalents of Acr+–Mes to produce two equivalents of Acr•-Mes that reduce protons to produce H2 in the presence of an H2 evolution catalyst. Acr+-Mes can also be applied to photocatalytic generation of H2, accompanied by dehydrogenative oxygenation of an alkene and selective C(sp2)-H amination of arenes. A one-photon two-electron process is also made possible by a bimolecular reaction of the excited state of a metal-hydride complex with the ground state complex to produce H2.
|Title of host publication
|Springer Science and Business Media Deutschland GmbH
|Number of pages
|Published - 2022
Bibliographical noteFunding Information:
The authors gratefully acknowledge the contributions of their collaborators and coworkers mentioned in the cited references, and financial supports from a SENTAN project from JST and JSPS KAKENHI (Grant Numbers 16H02268 to S.F.) from MEXT, Japan, and from the NRF of Korea through CRI (NRF-2021R1A3B1076539 to W.N), GRL (NRF-2010-00353 to W.N.), and Basic Science Research Program (2020R1I1A1A01074630 to Y.M.L. and 2017R1D1A1B03032615 to S.F.).
© 2022, Springer Nature Switzerland AG.
- Electron transfer
- Hydrogen evolution
- Metal-hydride complex
- Reaction mechanism