Metal Oxide Nanocluster Modifed
TiO2 Photocatalysts
Marco Fronzi and Michael Nolan
Tyndall National Institute, University College of Cork, Lee Maltings, Dyke Parade, Cork, Ireland
[email protected], [email protected]
Motivation
Modifications of TiO2 are intensively studied as
photocatalysts such as solar water splitting or solar CO 2
reduction, both of which can produce useful fuels using solar
energy. To date, substitutional doping of Ti and/or O sites is
the most widely studied approach but suffers from practical
problems. We have developed an alternative approach –
modification of TiO2 surfaces with nanoclusters of metaloxides with the aim to
Shift light absorption into the visible region
●Enhance electron-hole separation
●Provide reactive sites for H Oor CO
to interact and O
2
2
vacancies to form
Ti5O10
Ti6O12
Ti16O32
Ti30O60
2
Visible light
●
The work has been undertaken in cooperation with Prof. H.
Hada (Japan) and Prof. K. Gray / E. Weitz / J. Notestein
(Northwestern) & Prof. T. Byrne (Ulster) and it was facilitated
by awards of computing time on ICHEC (Stokes, Fionn) and
through PRACE Tier-1
3
1
Target
●Visible Light harvest
●Efficient Charge
separation
●Enhancement of Catalytic
activity
[1] Scanning TEM image indicates 15–20 nm crystallites. High-resolution TEM (inset) confirms the presence of crystalline anatase. (b) Magnified SEM image of
the film. (c) Large area SEM image of the film. (d) AFM image showing 100–200 nm self-sintered TiO2 grains. (e) Conductive AFM topography map. (f)
Conductive AFM current map.
[2] Photo-Catalytic activity conversion of CH4
[3] CO2 conversion and Methanol selectivity as a function of the TiO2 content
Ti8O16
Ti30O60 1.5 nm => experimental cluster size
Push VB edge to higher energy – red shift
After excitation – electron on TiO2 surface and
hole on titanyl oxygen of TiO2 Nanocluster
What Happens with Water?
Water on rutile (110)
No change in the VB
edge on the wet
surface Different from
Nanocluster on the dry
TiO2 surface
Water interacting with TiO2 nanocluster
Eads = -2.16 eV
Eads =-1.53 eV
Eads = -6.54 eV at full H2O coverage
Dissociative adsorption more favourable
No change in the VB upshift
H migration from surface –OH to the TiO2 nanocluster
Titanyl Group is removed by O-H bond formation
TiO2 Anatase Modified with p-block Oxide Nanoclusters
MgO-Anatase (101)
MgO-Anatase-OH (101)
SnO-Anatase (101)
What if the
surface is wet?
References
[1] B. Reeja-Jayan, Katharine L. Harrison, K. Yang, Chih-Liang Wang, A. E. Yilmaz and Arumugam Manthiram Scientific Reports 2, 1003 (2012)
[2] Jie Xiao, Prof. Dongsen Mao, Dr. Xiaoming Guo and Dr. Jun Yu Energy Technol. 3, 32–39 (2015)
[3] V. Vaiano, D. Sannino and P. Ciambelli Photochem. Photobiol. Sci. 14, 550–555 (2015)
SnO-Anatase-OH (101)