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Title: First Principles Insight into H2 Activation and Hydride Species on TiO2 Surfaces

Abstract

Hydrogen interaction with the TiO2 surfaces is important in many catalytic and photocatalytic reactions. However, the mechanisms of H2 activation on TiO2 surfaces remain unclear. Here in this work, we study H2 activation on the most commonly examined and stable surfaces of different TiO2 polymorphs, including rutile TiO2(110), anatase TiO2(101), and brookite TiO2(210), by first-principles density functional theory. We find that for all three surfaces, the heterolytic pathway is kinetically more favorable (leading to a hydride and a hydroxyl), even though the homolytic dissociation of H2 is thermodynamically more favorable (leading to two hydroxyls). For rutile TiO2(110), the hydride produced by the heterolytic dissociation of H2 can transfer from Ti to O with an activation energy of 0.99 eV, yielding the homolytic products. For anatase TiO2(101) and brookite TiO2(210), the barrier of hydrogen transfer from Ti to O is higher (1.48–1.68 eV). This indicates that hydrides on can be kinetically stabilized on TiO2 surfaces. In conclusion, our study sheds light on the mechanisms of H2 dissociation on TiO2 and provides rational for the existence of hydrides on TiO2 or other reducible metal oxides which may facilitate hydrogenation reactions.

Authors:
 [1]; ORCiD logo [2]; ORCiD logo [1]
  1. Univ. of California, Riverside, CA (United States). Department of Chemistry
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Chemical Sciences Division and Center for Nanophase Materials Sciences
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Chemical Sciences, Geosciences & Biosciences Division
OSTI Identifier:
1468080
Grant/Contract Number:  
AC05-00OR22725; AC02-05CH11231
Resource Type:
Accepted Manuscript
Journal Name:
Journal of Physical Chemistry. C
Additional Journal Information:
Journal Volume: 122; Journal Issue: 35; Journal ID: ISSN 1932-7447
Publisher:
American Chemical Society
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 08 HYDROGEN

Citation Formats

Hu, Guoxiang, Wu, Zili, and Jiang, De-en. First Principles Insight into H2 Activation and Hydride Species on TiO2 Surfaces. United States: N. p., 2018. Web. doi:10.1021/acs.jpcc.8b05251.
Hu, Guoxiang, Wu, Zili, & Jiang, De-en. First Principles Insight into H2 Activation and Hydride Species on TiO2 Surfaces. United States. doi:10.1021/acs.jpcc.8b05251.
Hu, Guoxiang, Wu, Zili, and Jiang, De-en. Thu . "First Principles Insight into H2 Activation and Hydride Species on TiO2 Surfaces". United States. doi:10.1021/acs.jpcc.8b05251. https://www.osti.gov/servlets/purl/1468080.
@article{osti_1468080,
title = {First Principles Insight into H2 Activation and Hydride Species on TiO2 Surfaces},
author = {Hu, Guoxiang and Wu, Zili and Jiang, De-en},
abstractNote = {Hydrogen interaction with the TiO2 surfaces is important in many catalytic and photocatalytic reactions. However, the mechanisms of H2 activation on TiO2 surfaces remain unclear. Here in this work, we study H2 activation on the most commonly examined and stable surfaces of different TiO2 polymorphs, including rutile TiO2(110), anatase TiO2(101), and brookite TiO2(210), by first-principles density functional theory. We find that for all three surfaces, the heterolytic pathway is kinetically more favorable (leading to a hydride and a hydroxyl), even though the homolytic dissociation of H2 is thermodynamically more favorable (leading to two hydroxyls). For rutile TiO2(110), the hydride produced by the heterolytic dissociation of H2 can transfer from Ti to O with an activation energy of 0.99 eV, yielding the homolytic products. For anatase TiO2(101) and brookite TiO2(210), the barrier of hydrogen transfer from Ti to O is higher (1.48–1.68 eV). This indicates that hydrides on can be kinetically stabilized on TiO2 surfaces. In conclusion, our study sheds light on the mechanisms of H2 dissociation on TiO2 and provides rational for the existence of hydrides on TiO2 or other reducible metal oxides which may facilitate hydrogenation reactions.},
doi = {10.1021/acs.jpcc.8b05251},
journal = {Journal of Physical Chemistry. C},
number = 35,
volume = 122,
place = {United States},
year = {2018},
month = {8}
}

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