%0 Journal Article
%A Herron, Jeffrey A.
%A Ferrin, Peter
%A Mavrikakis, Manos
%D 2014
%T First-Principles
Mechanistic Analysis of Dimethyl Ether Electro-Oxidation on Monometallic
Single-Crystal Surfaces
%U https://acs.figshare.com/articles/journal_contribution/First_Principles_Mechanistic_Analysis_of_Dimethyl_Ether_Electro_Oxidation_on_Monometallic_Single_Crystal_Surfaces/2241955
%R 10.1021/jp505919x.s001
%2 https://acs.figshare.com/ndownloader/files/3877894
%K Ru
%K Re
%K surface poisoning species
%K fuel cells
%K Rh
%K 12 model
%K OH
%K order Cu
%K surfaces increases
%K catalyst activity
%K Pt
%K theory calculations
%K Pd
%K thermochemistry
%K PW
%K step level
%K DME fuel cells
%K oxidation
%K petroleum fuels
%K ethanol
%K CO 2
%K Ni
%K reaction paths
%K transition metals
%K catalyst design
%K energy density
%K dimethyl ether
%K phase diagram
%K Co
%K CO 2.
%K formic acid
%K methanol
%K reactivity descriptors
%K model system
%K Ag
%K Ir
%X Dimethyl
ether is an attractive alternative to petroleum fuels due to its physical
properties, comparable energy density to methanol and ethanol, and
minimal deleterious environmental/toxicological effects. For direct
fuel cells, it has a number of advantages over other prominent fuels,
including easier storage with respect to hydrogen, lower toxicity
and crossover when compared to methanol, and more facile complete
oxidation as compared to ethanol (which includes a relatively difficult
to break C–C bond). However, the dimethyl ether electro-oxidation
reaction is poorly understood, hindering the development of improved
electrocatalysts. Using periodic, self-consistent (PW91-GGA) density
functional theory calculations, we evaluate the thermochemistry of
dimethyl ether (DME) electro-oxidation, at the elementary step level,
on 12 model, closed-packed facets of pure transition metals: Au, Ag,
Cu, Pt, Pd, Ni, Ir, Rh, Co, Os, Ru, and Re. From the calculated thermochemistry,
we determine the most probable reaction paths on each of these surfaces,
focusing on Pt as a model system. Our results predict two key electro-oxidation
peaks. At lower potentials, there is a peak corresponding to partial
oxidation of DME to CO (and other surface poisoning species) or complete
oxidation to CO2 via formic acid as a key intermediate.
A second, higher-potential peak is due to complete oxidation of adsorbed
CO (and other surface poisoning species) to CO2. Assuming
the catalysts remain in their metallic state during the DME electro-oxidation
process, our results suggest that the onset potential of the surfaces
increases in the order Cu < Ni < Os < Rh < Ir < Co
< Ru < Pt < Ag < Pd < Re < Au. Using our results,
we construct a theoretical phase diagram showing predicted catalyst
activity based on two key reactivity descriptors, the free energies
of adsorbed CO and OH. We compare all results to methanol electro-oxidation
to understand key mechanistic differences and their impacts on optimal
catalyst design for direct DME fuel cells.
%I ACS Publications