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Optical properties of anatase TiO2: synergy between transition metal doping and oxygen vacancies

  • Julio César González-Torres
  • Luis A. Cipriano
  • Enrique Poulain
  • Víctor Domínguez-Soria
  • Raúl García-Cruz
  • Oscar Olvera-Neria
Original Paper

Abstract

Charge carriers (electrons and holes) are generated on the TiO2 using UV radiation; this excitation energy can be reduced by modifying the material electronic structure, for example, by doping or creating oxygen vacancies. Here, the electronic structure of a transition metal-doped anatase, bulk and surface, and their interaction with oxygen vacancies are studied using density functional theory. The visible light response of metal-doped TiO2 (101) is also determined. Transition metals generate intra-band gap states, which reduce the excitation energy but may also act as charge recombination sites. Dopants Fe, Co, and Ni remarkably enhance the visible light response due to the states in the middle of the gap. However, Co and Ni create heavier charge carriers. Our results show that Pd and Pt-doped TiO2 generate states near the valence and conduction band with a “clean” band gap (without states in the middle of the gap). Moreover, Pt-doped TiO2 maintains the charge mobility because it presents a small charge carriers mass. Hence, Pt-doped TiO2 represents the best alternative to activate TiO2 under visible light. The optical response of transition metal-doped TiO2 follows the order 3d > 4d > 5d. The oxygen vacancies reduce the response of metal-doped TiO2 to visible light because the unpaired electrons generated occupy the empty states of metal-doping.

Graphical Abstract

Density of states of TiO2 (101) surface doped with transition metals and oxygen vacancies

Keywords

Anatase TiO2 Transition metal doping Oxygen vacancies DFT Optical response 

Notes

Acknowledgments

O. Olvera-Neria thanks CONACYT-México for financial support of the project CB-2011-01/166246. The authors are indebted to the Laboratory of Applied Mathematics and High-Performance Computing for the computing time granted in the ABACUS I supercomputer. JGT is grateful to CONACYT-México for the studentship granted to pursue his doctoral studies.

Supplementary material

894_2018_3816_MOESM1_ESM.docx (1.2 mb)
ESM 1 (DOCX 1241 kb)

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Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Área de Física Atómica Molecular Aplicada (FAMA), CBIUniversidad Autónoma Metropolitana-AzcapotzalcoCiudad de MéxicoMexico
  2. 2.Área de Química Aplicada, CBIUniversidad Autónoma Metropolitana-AzcapotzalcoCiudad de MéxicoMexico

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