Issue 40, 2011

Effective increasing of optical absorption and energy conversion efficiency of anatase TiO2nanocrystals by hydrogenation

Abstract

Disorder-engineered nanophase anatase TiO2 through hydrogenation has been demonstrated to exhibit substantial solar-driven photocatalytic activities [X. Chen, L. Liu, P. Y. Yu, S. S. Mao, Science, 2011, 331, 746], while the detailed image of the disorder is unclear, and the role of the hydrogenation as well as the mechanism of high photoactivity is still ambiguous. Based on first-principles calculations, we find by taking into account the synergic effect of Ti–H and O–H bonds that hydrogen atoms can be chemically absorbed both on Ti5c and O2c atoms for (101), (001), and (100) surfaces, while previous studies predicted that chemical absorption of H on both Ti5c and O2c only takes place on the (001) surface due to overlooking the synergic effect. The hydrogenation induces obvious lattice distortions on (101) and (100) surfaces of nanoparticles enhancing the intraband coupling within the valence band, while the (001) surface is not largely affected. Different from the previous understanding that the lattice disorder accounts for the induced mid-gap states while the hydrogen only stabilizes the lattice disorders by passivating their dangling bonds, we find that the adatoms not only induce the lattice disorders but also interact strongly with the Ti 3d and O 2p states, resulting in a considerable contribution to the mid-gap states. The optical absorption is dramatically red shifted due to the mid-gap states and the photogenerated electron–hole separation is substantially promoted as a result of electron–hole flow between different facets of hydrogenated nanoparticles, which may account for the exceptional high energy conversion efficiency under solar irradiation. Even more interestingly, we find that hydrogenation reverses the redox behavior of different surfaces of nanoparticles, which provides new hints that one can tune the photoexcited electron–hole flow between different surfaces of nanoparticles in accordance to one's request by appropriate chemical surface treatment. We believe that band-offset-engineering between different facets of nanocrystals can be an effective way to facilitate energy conversion efficiency and should be applicable to other nanophase materials.

Graphical abstract: Effective increasing of optical absorption and energy conversion efficiency of anatase TiO2 nanocrystals by hydrogenation

Supplementary files

Article information

Article type
Paper
Submitted
14 Jun 2011
Accepted
26 Aug 2011
First published
14 Sep 2011

Phys. Chem. Chem. Phys., 2011,13, 18063-18068

Effective increasing of optical absorption and energy conversion efficiency of anatase TiO2 nanocrystals by hydrogenation

J. Lu, Y. Dai, H. Jin and B. Huang, Phys. Chem. Chem. Phys., 2011, 13, 18063 DOI: 10.1039/C1CP22726B

To request permission to reproduce material from this article, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements