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The Influence of Surface Reconstruction and C-impurities on Photocatalytic Water Dissociation by TiO2

Published online by Cambridge University Press:  26 February 2011

Xiliang Nie  and
Karl Sohlberg
Xiliang Nie
Affiliation:
Department of Chemistry, Drexel University, Philadelphia, PA 19104
Karl Sohlberg
Affiliation:
Department of Chemistry, Drexel University, Philadelphia, PA 19104
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Abstract

TiO2 is well known as a prototype photocatalyst for water dissociation. To understand the mechanism of its photocatalytic water dissociation we performed first-principles calculations. We find that the surface of the catalytically favorable (TiO) termination is very different from the physically favorable (oxygen) termination. The calculated surface energy of the catalytically favorable (TiO) termination is about 10 times larger than that of the physically favorable (oxygen) termination. Analysis of the surface band structure suggests that while O-vacancies are intrinsic active sites for water dissociation into H2 and O2 gas, they are not essential for photocatalytic water dissociation. We also find that carbon impurities decrease the band-gap of TiO2, in agreement with previously reported experimental results. Moreover, we identify the origin of the arcane “double band gap” in carbon doped TiO2. The two onsets seen in the photoabsorption spectrum result from excitations from two of three C p-states within the band gap, not from domains of different composition.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 801: Symposium BB – Materials and Technologies for a Hydrogen Economy , 2003 , BB6.6
Copyright
Copyright © Materials Research Society 2004

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References

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