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Study of Excited States and Electron Transfer of Semiconductor‐Metal‐Complex Hybrid Photocatalysts for CO 2 Reduction by Using Picosecond Time‐Resolved Spectroscopies
Author(s) -
Sato Shunsuke,
Tanaka Sei'ichi,
Yamanaka Kenichi,
Saeki Shu,
Sekizawa Keita,
Suzuki Tomiko M.,
Morikawa Takeshi,
Onda Ken
Publication year - 2021
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.202004068
Subject(s) - photoexcitation , photocatalysis , semiconductor , electron transfer , picosecond , excited state , photochemistry , materials science , catalysis , chemistry , optoelectronics , atomic physics , optics , laser , biochemistry , physics
A semiconductor‐metal‐complex hybrid photocatalyst was previously reported for CO 2 reduction; this photocatalyst is composed of nitrogen‐doped Ta 2 O 5 as a semiconductor photosensitizer and a Ru complex as a CO 2 reduction catalyst, operating under visible light (>400 nm), with high selectivity for HCOOH formation of more than 75 %. The electron transfer from a photoactive semiconductor to the metal‐complex catalyst is a key process for photocatalytic CO 2 reduction with hybrid photocatalysts. Herein, the excited‐state dynamics of several hybrid photocatalysts are described by using time‐resolved emission and infrared absorption spectroscopies to understand the mechanism of electron transfer from a semiconductor to the metal‐complex catalyst. The results show that electron transfer from the semiconductor to the metal‐complex catalyst does not occur directly upon photoexcitation, but that the photoexcited electron transfers to a new excited state. On the basis of the present results and previous reports, it is suggested that the excited state is a charge‐transfer state located between shallow defects of the semiconductor and the metal‐complex catalyst.