Topics in Current Chemistry (2019) 377:11
1 3
of Pt ML /Au(111) is ascribed to Pt ML that is stretched by over 4%. Such monolayer
enhances dehydrogenative adsorption of alcohol molecules (Pt–CO) and the dissociation of water (Pt–OH formation). That is, the strain effect due to the Au
support results in a Pt ML that is able to bind the adsorbates strongly enough to
activate methanol and carry on the reaction to the formation of CO 2 , yet weakly
enough to prevent CO poisoning [25].
Several Pt ML nanocatalysts comprising Pt ML supported on mono- or bimetallic nanoparticle cores were studied (Fig. 21), and the activity for both
methanol and ethanol electrooxidation reactions increased in the order of Pt ML /
Pd/C < Pt/C < Pt ML /Au/C. Hence, a qualitatively similar trend is observed as with
single-crystal surfaces, viz., activity of dilated Pt ML is enhanced while that of
compressed Pt ML is decreased. Pt ML supported on Pd–Au bimetallic alloy nanoparticles demonstrated an activity in between of Pt ML /Pd/C and Pt ML /Au/C, which
suggests further that a tunable activity can be obtained from Pt ML by manipulating its lateral strain [32].
6 Conclusions
Despite the renewed interest in ethanol oxidation reaction, there is still a long way
to go before an active, cost-effective catalyst is found for the large-scale adaptation
in direct ethanol fuel cells. At present, the best catalysts in acidic solution contain
a certain amount of noble metals. Particularly, the best catalyst that leads to preferential production of CO 2 as the main product contains nanoparticles of Pt/Rh solid
solution, where the role of the latter metal is to break the C–C bond of ethanol.
However, Rh is several times more expensive than Pt, so reducing the amount of
noble metals and/or replacing them with cheaper alternatives is the major challenge.
Another possible pathway is through a design of core–shell nanoparticles with the
active catalyst in a form of a monolayer deposited on an inexpensive and abundant
core. The size, shape, and structure of nanoparticle supports can affect the reactivity, selectivity, and stability of the active monolayer in a complex way, where lateral
strain of the monolayer may be an important factor. However, with advanced synthetic nanotechnology methods designing suitable, low-cost nanoparticle supports
with enhancing properties is quite feasible.
Acknowledgements This research was performed at Brookhaven National Laboratory under contract
DE-SC0012704 with the US Department of Energy, Office of Basic Energy Science, Material Science
and Engineering Division, Division of Chemical Sciences, Geosciences and Biosciences Division.
X-ray absorption studies were conducted on National Synchrotron Light Source (NSLS) at Brookhaven
National Laboratory, in Upton, NY, and Stanford Synchrotron Light Source (SSRL) at SLAC National
Accelerator Laboratory in Stanford, CA. The authors are indebted to the beamline staff Sayed Khalid
(NSLS) and Matthew Latimer (SSRL) for their help. Beamlines X18a, X18b, and X19A at the NSLS,
as well as BL 2–2 at the SSRL were supported in part by the Synchrotron Catalysis Consortium, U.S.
Department of Energy Grant no. DE-SC0012335.
Reprinted from the journal
34
1 3
of Pt ML /Au(111) is ascribed to Pt ML that is stretched by over 4%. Such monolayer
enhances dehydrogenative adsorption of alcohol molecules (Pt–CO) and the dissociation of water (Pt–OH formation). That is, the strain effect due to the Au
support results in a Pt ML that is able to bind the adsorbates strongly enough to
activate methanol and carry on the reaction to the formation of CO 2 , yet weakly
enough to prevent CO poisoning [25].
Several Pt ML nanocatalysts comprising Pt ML supported on mono- or bimetallic nanoparticle cores were studied (Fig. 21), and the activity for both
methanol and ethanol electrooxidation reactions increased in the order of Pt ML /
Pd/C < Pt/C < Pt ML /Au/C. Hence, a qualitatively similar trend is observed as with
single-crystal surfaces, viz., activity of dilated Pt ML is enhanced while that of
compressed Pt ML is decreased. Pt ML supported on Pd–Au bimetallic alloy nanoparticles demonstrated an activity in between of Pt ML /Pd/C and Pt ML /Au/C, which
suggests further that a tunable activity can be obtained from Pt ML by manipulating its lateral strain [32].
6 Conclusions
Despite the renewed interest in ethanol oxidation reaction, there is still a long way
to go before an active, cost-effective catalyst is found for the large-scale adaptation
in direct ethanol fuel cells. At present, the best catalysts in acidic solution contain
a certain amount of noble metals. Particularly, the best catalyst that leads to preferential production of CO 2 as the main product contains nanoparticles of Pt/Rh solid
solution, where the role of the latter metal is to break the C–C bond of ethanol.
However, Rh is several times more expensive than Pt, so reducing the amount of
noble metals and/or replacing them with cheaper alternatives is the major challenge.
Another possible pathway is through a design of core–shell nanoparticles with the
active catalyst in a form of a monolayer deposited on an inexpensive and abundant
core. The size, shape, and structure of nanoparticle supports can affect the reactivity, selectivity, and stability of the active monolayer in a complex way, where lateral
strain of the monolayer may be an important factor. However, with advanced synthetic nanotechnology methods designing suitable, low-cost nanoparticle supports
with enhancing properties is quite feasible.
Acknowledgements This research was performed at Brookhaven National Laboratory under contract
DE-SC0012704 with the US Department of Energy, Office of Basic Energy Science, Material Science
and Engineering Division, Division of Chemical Sciences, Geosciences and Biosciences Division.
X-ray absorption studies were conducted on National Synchrotron Light Source (NSLS) at Brookhaven
National Laboratory, in Upton, NY, and Stanford Synchrotron Light Source (SSRL) at SLAC National
Accelerator Laboratory in Stanford, CA. The authors are indebted to the beamline staff Sayed Khalid
(NSLS) and Matthew Latimer (SSRL) for their help. Beamlines X18a, X18b, and X19A at the NSLS,
as well as BL 2–2 at the SSRL were supported in part by the Synchrotron Catalysis Consortium, U.S.
Department of Energy Grant no. DE-SC0012335.
Reprinted from the journal
34