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2012-08-15
A Review on the Visible Light Active Titanium Dioxide A Review on the Visible Light Active Titanium Dioxide
Photocatalysts for Environmental Applications Photocatalysts for Environmental Applications
Miguel Pelaez
University of Cincinnati
Nicholas Nolan
Technological University Dublin
Suresh Pillai
Technological University Dublin
, suresh.pillai@tudublin.ie
See next page for additional authors
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Recommended Citation Recommended Citation
Pelaez, M. et al (2012). A Review on the Visible Light Active Titanium Dioxide Photocatalysts for
Environmental Applications.
Applied Catalysis B:Environmental
, vol. 125, pp. 331– 349. doi:10.1016/
j.apcatb.2012.05.036
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Authors Authors
Miguel Pelaez, Nicholas Nolan, Suresh Pillai, Michael Seery, Polycarpos Falaras, Athanassios G. Kontos,
Patrick S.M. Dunlop, Jeremy W.J. Hamiltone, J. Anthony Byrne, Kevin O’Shea, Mohammad H. Entezari, and
Dionysios D. Dionysiou
This article is available at ARROW@TU Dublin: https://arrow.tudublin.ie/ehsiart/2
Accepted Manuscript
Title: A review on the visible light active titanium dioxide
photocatalysts for environmental applications
Authors: Miguel Pelaez, Nicholas T. Nolan, Suresh C. Pillai,
Michael K. Seery, Polycarpos Falaras, Athanassios G. Kontos,
Patrick S.M. Dunlop, Jeremy W.J. Hamilton, J.Anthony
Byrne, Kevin O’shea, Mohammad H. Entezari, Dionysios D.
Dionysiou
PII: S0926-3373(12)00239-1
DOI: doi:10.1016/j.apcatb.2012.05.036
Reference: APCATB 12094
To appear in: Applied Catalysis B: Environmental
Received date: 28-3-2012
Revised date: 21-5-2012
Accepted date: 25-5-2012
Please cite this article as: M. Pelaez, N.T. Nolan, S.C. Pillai, M.K. Seery, P.
Falaras, A.G. Kontos, P.S.M. Dunlop, J.W.J. Hamilton, J.A. Byrne, K. O’shea, M.H.
Entezari, D.D. Dionysiou, A review on the visible light active titanium dioxide
photocatalysts for environmental applications*, Applied Catalysis B, Environmental
(2010), doi:10.1016/j.apcatb.2012.05.036
This is a PDF file of an unedited manuscript that has been accepted for publication.
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Page 1 of 54
Accepted Manuscript
1
A review on the visible light active titanium dioxide photocatalysts for 1
environmental applications* 2
3
4
MIGUEL PELAEZ,
1
NICHOLAS T. NOLAN,
2
SURESH C. PILLAI,
2
MICHAEL K. SEERY,
3
5
POLYCARPOS FALARAS,
4
ATHANASSIOS G. KONTOS,
4
PATRICK S.M. DUNLOP,
5
JEREMY 6
W.J. HAMILTON,
5
J.ANTHONY BYRNE,
5
KEVIN O‟SHEA,
6
MOHAMMAD H. ENTEZARI
7
and 7
DIONYSIOS D. DIONYSIOU
1,
§
8
9
10
1
Environmental Engineering and Science Program, School of Energy, Environmental, Biological, and 11
Medical Engineering, University of Cincinnati, Cincinnati, Ohio 45221-0071, USA 12
2
Center for Research in Engineering Surface Technology (CREST) 13
DIT FOCAS Institute, Kevin St, Dublin 8, Ireland 14
3
School of Chemical and Pharmaceutical Sciences, Dublin Institute of Technology, Kevin St., Dublin 8, 15
Ireland 16
4
Institute of Physical Chemistry, NCSR Demokritos, 15310 Aghia Paraskevi, Attiki, Greece 17
5
Nanotechnology and Integrated BioEngineering Centre, School of Engineering, University of Ulster, 18
Northern Ireland, BT37 0QB, United Kingdom 19
6
Department of Chemistry and Biochemistry, Florida International University, University Park, Miami, 20
Florida 3319, USA 21
7
Department of Chemistry, Ferdowsi University of Mashhad, Mashhad, 91775, IRAN 22
23
* All authors have contributed equally to this review. 24
25
§Corresponding author phone: (513) 556-0724; fax: (513) 556-2599; e-mail: 26
dionysios.d.dionysiou@uc.edu. 27
*Manuscript
Page 2 of 54
Accepted Manuscript
2
Abstract 1
2
Fujishima and Honda (1972) demonstrated the potential of titanium dioxide (TiO
2
) 3
semiconductor materials to split water into hydrogen and oxygen in a photo-4
electrochemical cell. Their work triggered the development of semiconductor 5
photocatalysis for a wide range of environmental and energy applications. One of the 6
most significant scientific and commercial advances to date has been the development of 7
visible light active (VLA) TiO
2
photocatalytic materials. In this review, a background on 8
TiO
2
structure, properties and electronic properties in photocatalysis is presented. The 9
development of different strategies to modify TiO
2
for the utilization of visible light, 10
including non metal and/or metal doping, dye sensitization and coupling semiconductors 11
are discussed. Emphasis is given to the origin of visible light absorption and the reactive 12
oxygen species generated, deduced by physicochemical and photoelectrochemical 13
methods. Various applications of VLA TiO
2
, in terms of environmental remediation and 14
in particular water treatment, disinfection and air purification, are illustrated. 15
Comprehensive studies on the photocatalytic degradation of contaminants of emerging 16
concern, including endocrine disrupting compounds, pharmaceuticals, pesticides, 17
cyanotoxins and volatile organic compounds, with VLA TiO
2
are discussed and 18
compared to conventional UV-activated TiO
2
nanomaterials. Recent advances in bacterial 19
disinfection using VLA TiO
2
are also reviewed. Issues concerning test protocols for real 20
visible light activity and photocatalytic efficiencies with different light sources have been 21
highlighted. 22
23
24
Keywords: TiO
2
, visible, solar, water, treatment, air purification, disinfection, non-metal 25
doping, anatase, rutile, N-TiO
2
, metal doping, environmental application, reactive 26
oxygen species, photocatalysis, photocatalytic, EDCs, cyanotoxins, emerging pollutants. 27
28
29
1. Titanium dioxide- an Introduction 30
31
1.1 TiO
2
structures and properties 32
33
Titanium dioxide (TiO
2
) exists as three different polymorphs; anatase, rutile and brookite 34
[1]. The primary source and the most stable form of TiO
2
is rutile. All three polymorphs 35
can be readily synthesised in the laboratory and typically the metastable anatase and 36
brookite will transform to the thermodynamically stable rutile upon calcination at 37
temperatures exceeding ~600 °C [2]. In all three forms, titanium (Ti
4+
) atoms are co-38
ordinated to six oxygen (O
2-
) atoms, forming TiO
6
octahedra [3]. Anatase is made up of 39
corner (vertice) sharing octahedra which form (001) planes (Figure 1a) resulting in a 40
tetragonal structure. In rutile the octahedra share edges at (001) planes to give a 41
tetragonal structure (Figure 1b), and in brookite both edges and corners are shared to give 42
an orthorhombic structure (Figure 1c) [2,4-7]. 43
44
Titanium dioxide is typically an n-type semiconductor due to oxygen deficiency [8]. The 45
band gap is 3.2 eV for anatase, 3.0 eV for rutile, and ~3.2 eV for brookite [9-11]. Anatase 46
