1. COLLEGE OF ENGINEERING Chemical, Biological &
Environmental Engineering
Introduction
As conventional energy sources begin to deplete, the need for alternative, renewable energy has
become necessary. Fuel cells have the potential to supply enough energy to power individual homes
and vehicles, as well as small, mobile devices in a cost effective and environmentally friendly manner.
Dimethyl ether (DME) is a promising fuel source that could fulfill these demands. Compared to other
well-known fuels, such as methanol or ethanol, a DME fuel cell is less toxic and stores hydrogen
more efficiently, the latter a great benefit with respect to employing fuel cells in smaller devices.
Surface Structure Sensitivity of Carbon-Oxygen
Bond Breakage within the Anode of a DME Fuel Cell
Yousif Almulla, Merissa Schneider-Coppolino and Líney Árnadóttir
School of Chemical, Biological, and Environmental Engineering
Oregon State University, Corvallis, Oregon
Methods
In conjunction with DFT, the Vienna Ab-initio Simulation Package (VASP) was used to model our
anode systems and to calculate system energies. DFT uses approximations of the Schrodinger equation
to model electron densities in atomic systems.
Different Surface Structures
Background
To produce the most efficient and effective
DME fuel cells, it is necessary to understand
the DME oxidation reaction on different
catalyst and catalyst structures. Experimental
studies have shown that the reaction rate of
dimethyl ether is different on Pt(100) and
Pt(111) surfaces. Here we use density
functional theory (DFT) to study the structural
sensitivity of the initial steps of DME
dissociation on platinum and nickel surfaces.
Different adsorption sites and configurations of
DME and C-O bond breaking dissociation
products (CH3O + CH3) are evaluated on two
different surface structures: fcc(100) and
fcc(111) for the two metals.
Figure 5: fcc (111) Adsorption Sites
Top Site
Bridge
Site
hcp
Hollow
fcc
Hollow
Figure 2: fcc (111) Side View
Figure 4: fcc (100) Side View
Figure 1: fcc (111) Top View
Figure 3: fcc (100) Top View
Results and Discussion
Platinum Nickel
fcc
(100)
fcc
(111)
Oxygen Down at Top Site
Adsorption Energy: -0.175 eV
Carbon Down at Bridge Site
Adsorption Energy: -0.113 eV
Carbon Down at Top Site
Adsorption Energy: -0.150 eV
Carbon Down at hcp Hollow
Adsorption Energy: -0.118 eV
Oxygen Down at Top Site
Adsorption Energy: -0.296 eV
Oxygen Down at Hollow Site
Adsorption Energy: -0.075 eV
a=3.976
a=3.514
-18.5
-18.0
-17.5
-17.0
-16.5
-16.0
-15.5
3.35 3.55 3.75 3.95 4.15
Energy(eV)
Lattice Constants (Å)
Platinum
Nickel
Acknowledgements
• Oregon State University Honors College
• Johnson Scholarship Program
• Dr. Liney Árnadóttir
• Graduate Students Lynza Halberstadt,
Dennis Petersen, and Qin Pang
Lattice Constants
Optimal lattice constants (a) were found, as
shown in the graph below, for both Platinum
and Nickel. These agree with experimentally
determined lattice constants, which were
found to be 3.912 and 3.499 for Platinum
and Nickel, respectively.
Adsorption
Energy
System
Energy
Surface
Energy
Adsorbate
Energy
Future Work
Next steps in this research include finding
the net change in energy after dissociation
of DME, and the activation energy of
dissociation for various surface
configurations, using the Nudged Elastic
Band (NEB) method. Both of these
energies are imperative to determining
the most promising material and material
structure for the anode catalyst. We would
also like to test more complex surfaces,
such as fcc(211) and fcc(355).
The final results will be useful for
determining potential surface structures
before conducting research within
experimental labs.
Different sites attract and repel
adsorbates differently based on the
relative proximity of electrons, and
electron density.
The adsorption energies were calculated for many different surface configurations. The
table below summarizes our initial findings for six different configurations. The Nickel
fcc(111) surface has shown the lowest adsorption energy, meaning that it has the most
favorable binding site.
References
Giustino, Feliciano. Material Modelling using Density
Functional Theory. United Kingdom: Oxford University Press,
2014. Print.
Richard, Masel I. Principles of Adsorption and Reaction on
Solid Surfaces. New York: John Wiley & Sons INC., n.d. 38-57.
Wiley Series in Chemical Engineering. Print.
Sholl, David S., and Janice A. Steckel. Density Functional
Theory A Practical Introduction. New Jersey: John Wiley &
Sons INC., 2009. Print.
Wheeler, Davey P. "Precision Measurements of the Lattice
Constants of Twelve Common Metals." Physical
Reviews 25.753 (1925). Web. 2015.