Nanotechnology in Electrochemical Energy Conversion and Storage
U. Stimming1,2,3, H. Wolfschmidt1
5
1
Department of Physics E19, Technische Universität München, Garching; 2Bavarian Centre of Applied Energy Research
(ZAE Bayern) Division I, Garching; 3nanoTUM, Technische Universität München, Garching, Germany
Recent
10
advances
in
electrocatalysis
show
that
on Cu results in a compressed lattice of Pt. On the other
nanoparticles, nanostructured surfaces and bimetallic
systems can have enhanced catalytic activity compared
hand, deposition of Pt on HOPG has only little effect on
the lattice of the deposited Pt due to weak binding of Pt
to bulk materials. This can be advantageously used in
electrochemical energy technology for various
to HOPG. Therefore, comparison of the results obtained
55 in these three systems can provide useful conclusions
applications such as fuel cells, batteries and electrolysis.
regarding the choice of substrate material.
Previous work on model electrodes such as Pd decorated
The successful preparation of bimetallic Bi-Pd catalysts
Au(111) and Pt decorated Au(111) surfaces showed
enhanced reactivity of the catalytic metal for hydrogen
supported on Sibunit carbon is a step towards new
60 catalyst
systems in fuel cells and batteries [8].
evolution reaction (HER) and hydrogen oxidation
[1-4]
20 reaction (HOR)
. In addition, by decreasing the
Transmission electron microscopy and local EDX
elemental analysis revealed that Bi-Pd/C catalysts
amount of Pd or Pt on Au(111) the activity increases as
contain bimetallic particles with narrow size distribution
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well. Two different approaches were pursued: Firstly, the
decoration of Au(111) single crystals surfaces with Pd
65
with maxima at 3.2–4.1 nm. It was shown that
modification of Pd/C by bismuth increases the specific
and Pt via defined electrodeposition to investigate
25 monolayers
and submonolayers of Pd and Pt[1-3].
activity of palladium towards HOR/HER by a factor of 3.
Secondly, the creation of single Pd and Pt particles using
the tip of an EC-STM. This tip was also used for
The results of fundamental as well as more applied
systems will be discussed in terms of catalytic behaviour
morphological characterization of the deposit and - out
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of tunnelling - it was used as a local sensor to determine
[3, 4]
30 the reactivity of the single particles
.
with promising properties for electrochemical energy
conversion. Important concepts in electrocatalysis will be
underlined with a special interest in the electrochemistry
on the nanometer scale.
A possible explanation of the observed increase could be
attributed to an effect of the substrate material due to
strained overlayers[5]. Eikerling et al.[6] showed that also
35
75
a direct involvement of the support as additional storage
References
for reaction intermediates can increase the catalytic
activity by the so called spill-over effect.
[1]
80
[3]
Therefore the choice of substrate material seems to be a
40
key parameter that plays an important role in the
electrocatalytic activity. In order to get a deeper
85
understanding of the substrate effects, we investigated
hydrogen related reactions such as HER and HOR on
three different large nanostructured surfaces. These
45
parameters of Pt result after deposition. Pt deposited on
50
Au(111) results in a strained lattice, while Pt deposited
[4]
[5]
[6]
[7]
90
systems are all based on Pt as catalyst material deposited
on Au(111), Cu and highly oriented pyrolytic graphite
(HOPG)[7] as substrate materials. The choice of substrate
reflects three cases in which changes in lattice
[2]
[8]
Pandelov, S. and Stimming, U. (2007) Electrochim. Acta,
52, 5548.
Wolfschmidt, H., Bußar, R. and Stimming, U. (2008) J.
Phys.: Condens. Matter 20, 374127.
Wolfschmidt, H.,Weingarth, D. and Stimming, U. (2010)
ChemPhysChem 11, 1533.
Meier, J. et. al, (2004) Chem. Phys. Lett. 390, 440.
Hammer, B. and Norskov, J.K. (1995) Surf. Sci., 343, 211.
Eikerling, M., Meier, J. and Stimming, U. (2003) Z. Phys.
Chem. (Int. Ed.) 217, 395.
Brülle, T. and Stimming, U. (2009) J. Electroanal. Chem.
636, 10.
O. Paschos et al. (2010) Electrochem. Commun.
oi:10.1016/j.elecom.2010.08.014
Corresponding author: stimming@ph.tum.de
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