Optical spectroscopic determination of photoexcited small-polaron hopping in transition metal oxide photocatalysts
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Ultrafast small-polaron formation profoundly shapes the electronic and catalytic behaviour of transition metal oxides (TMOs). Despite its significance, spectroscopic investigations of photoexcited polaron hopping in TMOs have been scarcely explored. Here, we present the first optical spectroscopic observation of photoexcited small-polaron hopping across the first-row TMOs, using femtosecond transient absorption spectroscopy. This polaronic feature rises within 500 fs as Drude-type absorption converts to localized, polaronic absorption. Fitting with a small-polaron optical conductivity model yields polaron relaxation energies of 400–650 meV, evidencing substantial energy loss upon self-trapping. Kinetic analysis shows that oxides with open d-shells localize charge most readily: polaron formation activation barriers are low in all TMOs (0–10 meV), whereas hopping barriers remain much higher (200–350 meV). This work establishes key spectroscopic and kinetic insights, highlighting the trade-off between charge localization and mobility, as well as the critical role of polaron formation in TMOs photocatalysts.
Date Issued
2026-01-05
Date Acceptance
2025-12-22
Citation
Chemical Science, 2026, 17 (8), pp.4203-4212
ISSN
2041-6520
Publisher
Royal Society of Chemistry (RSC)
Start Page
4203
End Page
4212
Journal / Book Title
Chemical Science
Volume
17
Issue
8
Copyright Statement
© 2026 The Author(s). Published by the Royal Society of Chemistry. Open Access Article. This article is licensed under a Creative Commons Attribution 3.0 Unported Licence.
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41522861
PII: d5sc08101g
Publication Status
Published
Coverage Spatial
England
Date Publish Online
2026-01-05