1. Figure 1. CO hydrogenation and chain propagation to
oxygenates as feedstock for lubricants, plasticizers,
and detergent
Methodology and Computational Setup
Background
Models Used
Effects of Cobalt Doping on OH/TiO2(110)
Oxygen Vacancy Formation Energy for
TiO2(110)
Acknowledgments
Financial support was provided by the National Science Foundation under contract No. CBET1438227.
Support was also provided in part by institutional funds made available to JSM by The Gene and Linda Voiland
School of Chemical Engineering and Bioengineering at Washington State University.
We would also like to thank Mr. Gregory Collinge, Mr. Renqin Zhang, Ms. Alyssa Hensley, Ms. Fanglin Che, and
Ms. Emily Anderst, for helpful comments, discussion, and the welcome constructive critiques.
Cobalt Dopant Effects on Oxygen Vacancy Formations in TiO2(110)
Adam Saleh1, Greg Collinge1, Jean-Sabin McEwen1*
1. Washington State University, Pullman, Washington 99164
*Corresponding author: js.mcewen@wsu.edu
Structural Optimization Calculations
o VASP code[6,7]
o Exchange-correlation (xc) functionals: GGA-PW91[8]
o PAW + planewave basis[9]
o Planewave kinetic cutoff energy of 500 eV
o Gaussian smearing of 0.2 eV
o Monkhorst-Pack k-point grid of 6  6  1
o ISMEAR=−5: tetrahedron
o Definition of vacancy formation energy (Evf):
Figure 2. 3D picture of p(2x1)
OH/TiO2(110) model expanded twice in
the x- and y- directions
 CO hydrogenation to higher alcohols over
CoCu-based heterogeneous catalysts an
alternative to energy-intensive process of
olefin hydroformylation [1-3]
 Higher alcohols used as chemical feedstock
for plastics and other highly desirable
products. Producing them from renewable CO
and H2 would be a significant step toward
carbon-neutral energy independence
 Experimental evidence suggests that the
presence of oxides plays a critical role in the
selectivity and activity of CoCu-based catalysts[1]
 A catalytically relevant characteristic of oxides
is their redox potential, which correlates to the
energy of oxygen vacancy formation.
A CB
Figure 3. Models A and B show a top and a side view of the O/TiO2(110) and OH/TiO2(110) respectively. Model C shows the
top and side view of an example ¼ ML Co-doped hydroxyl terminated titania surface.
Operp Obridge Ohollow
Surface - 1.59 2.78
interstitial 2.86 2.40 2.50
Operp Obridge Ohollow
Surface -----
Interstitial
Operp Obridge Ohollow
Surface - 1.49 2.48
interstitial 2.80 2.80 2.42
Table 1. Energy (eV) Formation vacancy of
OH/TiO2(110)
Table 2. Energy (eV) Formation vacancy of
O/TiO2(110)
Figure 4. Locations of the oxygen vacancies of the
OH/TiO2(110)
Ti1 Ti2 O3 Ti3
Obridge 5.66 4.83 3.57
Ohollow 0 0.00
Obridge
(farthest from Co)
5.43 - 3.05 -
Ohollow
(farthest from Co)
- -
Ti1 Ti2 O3 Ti3
Obridge
Ohollow
Obridge
(farthest from Co)
------
------
Ohollow
(farthest from Co)
------ ------
Table 3. Relative energy for oxygen vacancies with
Co adsorbed on OH/TiO2(110). [--] are non-
existent positions
Effects of Cobalt Doping on O/TiO2(110)
Ti1 O1 Ti2 O3 Ti3
Obridge 2.04 1.50 1.00 0.10 0.14
Ohollow 0.11 2.67 0.33
Obridge (farthest) 1.00 - - 0 -
Ohollow(farthest) - - 1.84 - 0.26
Ti1 O1 Ti2 O3 Ti3
Obridge
Ohollow
Obridge
(farthest from Co) ------ ------ ------
Ohollow
(farthest from Co) ------ ------ ------
Table 4. relative energy (eV) for oxygen vacancies with Co adsorbed on
O/TiO2(110)
Figure 7. Models of the oxygen vacancies with the different Co adsorption sites on
O/TiO2(110)
References
[1] Y. Xiang, R. Barbosa, N. Kruse, ACS Catal. 4 2014 2792-2800.
[2] Y. Xiang, R. Barbosa, X. Li, N. Kruse, ACS Catal. 5 2015 2929-2934.
[3] Y. Xiang, V. Chitry, P. Felfer, J. Cairney, S. Ringer, N. Kruse, J. Am. Chem. Soc. 135 2013 7114-7117.
[4] S. Julien, N. Kruse, ACS 134.39 2012 16135-16138.
[5] T. Pabisiak, A. Kiejna. Sol. State Comm. 144.7 2007 324-328.
[6] Buker, D. B., Todic, B., Ma, W., Jacobs, G., Davis, B. H., J. Catalysis, 2014, 228, 32-39
[7] Gnanamani, M. K., Catlysis Today, 2013, 25, 12-17
[8] Hibbitts, D. D., Loveless, B. T., Neurock, M., Iglesia, E., Angewandte Chemie intern‘l Ed. 2013, 52, 12273-12278
[9] Nilekar, A. U., Ruban, A. V., Mavrikakis, M. Surface Science, 2009, 603, 91-96 Liddicoat, P.
 As cobalt (Co) is the most active metal for chain-lengthening in CoCu [4], discovering its effect on
the formation of oxygen vacancies in TiO2 is of high interest.
 It has been shown that surface oxygen vacancy formation is much more facile than bulk oxygen
formation energy [5]
• Both oxygen and hydroxyl terminated surfaces are included since pH
conditions during catalyst preparation leads to the formation of hydroxyl
terminated surfaces, we include this system to account for the possibility of
such a system to exist under reaction conditions.
OH/TiO2(110)+1/2H2 → TiO2 + H2O
O/TiO2(110)+H2 → TiO2 + H2O
Ohollow
Obirdge
Obridge
(farthest from Co)
Ohollow
(farthest from Co)
Ohollow, I
Obridge, I
OPerpendicular
Obridge, S
Ohollow, S
Figure 6. Models of the oxygen vacancies with the different Co adsorption sites on O/TiO2(110)
• Ohollow removal with Co replacement is the most favorable Co/OH/TiO2(110)
O vacancy arrangement
Ohollow, Ti Ohollow Ti Optimized
Obridge (farthest from Co)
Obridge (farthest from Co)
optimized
• Obridge, removal with Co in the O3 hollow
site is the most favorable Co/O/TiO2(110)
O vacancy arrangement
Conclusion
O-vac
Layer
O-vac
Layer
O-vacancy
Starting Co
ads site
Starting Co
ads site
O-vac
Layer
Operp Obridge Ohollow
Surface -----
Interstitial
Figure 5. Locations of the oxygen vacancies of the
O/TiO2(110)
O-vac
Layer
O-vacancy
O-vacancy
Starting Co
ads site
Starting Co
ads site • Oxygen energy vacancy of
O/TiO2(110) is an
agreements with Pabisiak et
al. OH/TiO2(110) follows the
same trend.
• Ohollow removal with Co
replacement is the most
favorable Co/OH/TiO2(110)
O vacancy arrangement
• Obridge, removal with Co in
the O3 hollow site is the most
favorable Co/O/TiO2(110)
O vacancy arrangement
O-vacancy