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Title: Surface electron dynamics in hematite (α-Fe 2O 3): correlation between ultrafast surface electron trapping and small polaron formation

Abstract

Spectroscopically following charge carrier dynamics in catalytic materials has proven to be a difficult task due to the ultrafast timescales involved in charge trapping and the lack of spectroscopic tools available to selectively probe surface electronic structure. Transient extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy is able to follow surface electron dynamics due to its element, oxidation-state, and surface specificity, as well as the ultrafast time-resolution which can be achieved with XUV pulses produced by high harmonic generation. Here, we use ultrafast XUV-RA spectroscopy to show that charge localization and small polaron formation in Fe 2O 3 occur within ~660 fs. The photoexcitation of hematite at 400 nm initially leads to an electronically-delocalized ligand-to-metal charge transfer (LMCT) state, which subsequently evolves into a surface localized LMCT state. Comparison of the charge carrier dynamics for single and polycrystalline samples shows that the observed dynamics are negligibly influenced by grain boundaries and surface defects. Rather, correlation between experimental results and spectral simulations reveals that the lattice expansion during small polaron formation occurs on the identical time scale as surface trapping and represents the probable driving force for sub-ps electron localization to the hematite surface.

Authors:
ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]; ORCiD logo [1]
  1. The Ohio State University; Columbus; USA
Publication Date:
Research Org.:
The Ohio State Univ., Columbus, OH (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
1409484
Alternate Identifier(s):
OSTI ID: 1505562
Grant/Contract Number:  
SC0014051
Resource Type:
Published Article
Journal Name:
Chemical Science
Additional Journal Information:
Journal Volume: 8; Journal Issue: 12; Journal ID: ISSN 2041-6520
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY

Citation Formats

Husek, Jakub, Cirri, Anthony, Biswas, Somnath, and Baker, L. Robert. Surface electron dynamics in hematite (α-Fe2O3): correlation between ultrafast surface electron trapping and small polaron formation. United States: N. p., 2017. Web. doi:10.1039/c7sc02826a.
Husek, Jakub, Cirri, Anthony, Biswas, Somnath, & Baker, L. Robert. Surface electron dynamics in hematite (α-Fe2O3): correlation between ultrafast surface electron trapping and small polaron formation. United States. doi:10.1039/c7sc02826a.
Husek, Jakub, Cirri, Anthony, Biswas, Somnath, and Baker, L. Robert. Mon . "Surface electron dynamics in hematite (α-Fe2O3): correlation between ultrafast surface electron trapping and small polaron formation". United States. doi:10.1039/c7sc02826a.
@article{osti_1409484,
title = {Surface electron dynamics in hematite (α-Fe2O3): correlation between ultrafast surface electron trapping and small polaron formation},
author = {Husek, Jakub and Cirri, Anthony and Biswas, Somnath and Baker, L. Robert},
abstractNote = {Spectroscopically following charge carrier dynamics in catalytic materials has proven to be a difficult task due to the ultrafast timescales involved in charge trapping and the lack of spectroscopic tools available to selectively probe surface electronic structure. Transient extreme ultraviolet reflection-absorption (XUV-RA) spectroscopy is able to follow surface electron dynamics due to its element, oxidation-state, and surface specificity, as well as the ultrafast time-resolution which can be achieved with XUV pulses produced by high harmonic generation. Here, we use ultrafast XUV-RA spectroscopy to show that charge localization and small polaron formation in Fe2O3 occur within ~660 fs. The photoexcitation of hematite at 400 nm initially leads to an electronically-delocalized ligand-to-metal charge transfer (LMCT) state, which subsequently evolves into a surface localized LMCT state. Comparison of the charge carrier dynamics for single and polycrystalline samples shows that the observed dynamics are negligibly influenced by grain boundaries and surface defects. Rather, correlation between experimental results and spectral simulations reveals that the lattice expansion during small polaron formation occurs on the identical time scale as surface trapping and represents the probable driving force for sub-ps electron localization to the hematite surface.},
doi = {10.1039/c7sc02826a},
journal = {Chemical Science},
number = 12,
volume = 8,
place = {United States},
year = {2017},
month = {10}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: 10.1039/c7sc02826a

Citation Metrics:
Cited by: 9 works
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Works referenced in this record:

An ab initio model of electron transport in hematite (α-Fe2O3) basal planes
journal, April 2003

  • Rosso, Kevin M.; Smith, Dayle M. A.; Dupuis, Michel
  • The Journal of Chemical Physics, Vol. 118, Issue 14, p. 6455-6466
  • DOI: 10.1063/1.1558534