Issue 17, 2023

Water molecule switching heterogeneous proton-coupled electron transfer pathway


Figuring out the specific pathway of semiconductor-mediated proton-coupled electron transfer (PCET) driven by light is essential to solar energy conversion systems. In this work, we reveal that the amount of adsorbed water molecules determines the photo-induced PCET pathway on the TiO2 surface through systematic kinetic solvent isotope effect (KSIE) experiments. At low water content (<1.7 wt%), the photo-induced single-proton/single-electron transfer on TiO2 nanoparticles follows a stepwise PT/ET pathway with the formation of high-energy H+/D+–O[double bond, length as m-dash]C or H+/D+–O–C intermediates, resulting in an inverse KSIE (H/D) ∼0.5 with tBu3ArO· and KSIE (H/D) ∼1 with TEMPO in methanol-d0/d4 systems. However, at high water content (>2 wt%), the PCET reaction follows a concerted pathway with a lower energy barrier, leading to normal KSIEs (H/D) ≥ 2 with both reagents. In situ ATR-FTIR observation and DFT calculations suggest that water molecules' existence significantly lowers the proton/electron transfer energy barrier, which coincides with our experimental observations.

Graphical abstract: Water molecule switching heterogeneous proton-coupled electron transfer pathway

Supplementary files

Article information

Article type
Edge Article
23 Dec 2022
30 Mar 2023
First published
03 Apr 2023
This article is Open Access

All publication charges for this article have been paid for by the Royal Society of Chemistry
Creative Commons BY license

Chem. Sci., 2023,14, 4564-4570

Water molecule switching heterogeneous proton-coupled electron transfer pathway

Z. Liu, W. Peng, Y. Lin, X. Lin, S. Yin, S. Jia, D. Ma, Y. Yan, P. Zhou, W. Ma and J. Zhao, Chem. Sci., 2023, 14, 4564 DOI: 10.1039/D2SC07038C

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