XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
86
T3: O–5
Electrode potential triggered desolvation and resolvation of Ge(100)
in aqueous perchlorate electrolytes probed
by in-situ infrared spectroscopy
Fang Niu
1
, and Andreas Erbe
1,2
1 Department of Interface Chemistry and Surface Engineering, Max-Planck-Institut für
Eisenforschung GmbH, Max-Planck-Straße 1, 40237 Düsseldorf, Germany,e-mail: f.niu@mpie.de
2 Department of Materials Science and Engineering, NTNU, Norwegian University of Science and
Technology, 7491 Trondheim, Norway
Structural changes of the hydration shell of surfaces formed in aqueous solutions are
essential to many chemical, physical and biological phenomena. Attenuated total reflection
infrared (ATR-IR) spectroscopy is a powerful tool to investigate the hydration shells, via their
vibrational modes. Here, we present a study of the electrode potential dependence of the n-
Ge(100)/water interface probed by in situ and operando electrochemical ATR-IR spectroscopy.
Ge exhibits a potential-dependent transition from a hydroxide covered to hydrogen
terminated, hydrophobic surface when the applied potential is sufficiently negative [1]. As a
result, potential-dependent vibrational spectra of surface species and surface water were
obtained. Increased absorbance from the Ge-H stretching modes at negative potentials is
associated with an increased negative difference absorbance of water-related OH modes. When
the termination transition of germanium from OH to H termination occurs, the surface
consequently switches from a hydrophilic to a hydrophobic surface. During the reversible
switching, the interface water molecules are displaced from the surface by a “hydrophobic gap”.
The gap thickness was experimentally estimated to be ≈(1.9±0.1) Å. The resulting IR spectra of
the interfacial water in contact with the hydrophobic Ge-H show an increased absorbance of
non-hydrogen bound water appearing at 3640 cm
–1
under lower potentials (–0.59~–0.79 V) and
a decreased absorbance of strongly hydrogen bound water [2, 3]. Consequently, the existence of
free OH groups helps to investigate the real time potential dependent dynamics at the Ge/water
interface.
Fig. 1 The potential-dependent ATR-IR spectra on Ge(100) in Ar-saturated 0.1 M HClO
4
. Spectra were recorded
in direction of (left) decreasing electrode potentials and (right) increasing electrode potentials.
Keywords: in-situ ATR-IR; Ge/water interface; hydrophobic gap; free OH
Acknowledgment
This work is supported by the Cluster of Excellence RESOLV (EXC1069) funded by the Deutsche
Forschungsgemeinschaft within the framework of the German Excellence Initiative. The authors acknowledge the
MPIE machine shop for building the in situ experiment cells, Petra Ebbinghaus for technical assistance and
Simantini Nayak for helpful discussions.
References
[1] S. Nayak and A. Erbe, Phys. Chem. Chem. Phys. 18 (2016) 25100.
[2] F. Niu and A. Erbe, OSA Technical Digest (on-line), (2016), paper JW4A.14.
[3] F. Niu, R. Schulz, A. Castañeda Medina, R. Schmid, A. Erbe, Phys. Chem. Chem. Phys., submitted.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
87
T3: O–6
In situ spectroscopic studies of methane catalytic combustion
over Co, Ce, and Pd mixed oxides deposited on a steel surface
Przemysław J. Jodłowski
1
, Roman J. Jędrzejczyk
2
, Damian Chlebda
3
,
Maciej Gierada
1
, and Joanna Łojewska
3
1
Faculty of Chemical Engineering and Technology, Cracow University of Technology, Warszawska
24, 31-155 Kraków, Poland, e-mail: jodlowski@chemia.pk.edu.pl
2
Malopolska Centre of Biotechnology, Gronostajowa 7A, 30-387 Kraków, Poland
3
Jagiellonian University, Faculty of Chemistry, Ingardena 3, 30-060 Kraków, Poland
The study deals with the mechanism of methane catalytic combustion over structured cobalt
catalysts. The aim of this study was to correlate the information of the catalyst surface
intermediates during the methane combustion reaction investigated by in situ DRIFT
spectroscopy and catalytic tests. The series of cobalt and cobalt palldium nanocomposite
structured catalysts were obtained by impregnation method from nitrate solutions. Prior to the
impregnation step, the kanthal steel carriers were precalcined at high temperature and deposited
with the washcoat layer of γ-Al
2
O
3
. The catalyst surface was examined by XRF and in situ
μRaman spectroscopy.
The in situ experiments performed under methane oxidative and non-oxidative conditions
revealed that methoxy groups, formates/carbonates are active intermediates in methane catalytic
combustion. The kinetic experiments also revealed that palladium doped cobalt catalyst can be
considered as a good alternative for noble-based catalysts. Based on in situ experiments the
mechanism of methane catalytic combustion over cobalt-palladium doped γ-Al
2
O
3
was proposed
(Fig. 1).
Fig. 1. Reaction mechanism of methane combustion over cobalt palladium-doped catalyst [1].
Keywords: methane combustion; in situ DRIFT; μRaman; reaction mechanism; wire gauze; cobalt oxide
Acknowledgment
Financial support for this work was provided by the National Centre for Research and Development
LIDER/204/L-6/14/ NCBR/2015 and partly within Polish National Science Centre – Project No.
2013/09/B/ST8/00171. The authors are also grateful to the Polish National Science Centre – Project No.
2015/17/D/ST8/01252 for equipment for DRIFT analysis.
References
[1] P.J. Jodłowski, R.J. Jędrzejczyk, D. Chlebda, M. Gierada, J. Łojewska, J. Catal. 350 (2017) 1.
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