XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
262
T3: P–8
In situ FTIR study on active centres of metal oxide catalysts
for methane combustion
Magdalena A. Chrzan
1
, Damian K. Chleba
1
, Przemysław Jodłowski
2
, Ewelina
Salamon
1
, and Joanna Łojewska
1
1
Faculty of Chemistry, Jagiellonian University, ul. Ingardena 3, 30-060 Kraków, Poland,
e-mail: m.chrzan.1@gmail.com
2
Faculty of Chemical Engineering and Technology, Cracow University of Technology,
Warszawska 24, 30-155 Kraków, Poland
Methane catalytic combustion appears as an important problem for many practical reasons
connected with energy and environmental issues. At the same time the literature does not
provide a clear picture of the reaction mechanism even on the most active and commonly used
palladium catalyst. There are several reasons for which the mechanism is difficult to be
resolved. One of them originates from a huge energetic barrier of the C-H bond breakage which
proceeds according to radical mechanism. Due to analytical limitations exact steps that precede
this slowest step has not been recognized, yet. Although in situ FTIR results gathered by several
groups [1–4] attempted to assign the stable surface intermediate products of methane
combustion on Pd catalysts that come after the slowest step still ambiguous band assignment
prevents the formulation of the trustworthy parallel-consecutive oxidation pathways for methane
surface evolution. Finally, it is not elucidated whether the methane oxidation proceed via
adsorption step by forming methoxy groups according to Langmuir-Hinschelwood mechanism
or without adsorption by Rideal-Eley mechanism.
In this study the systematic evaluation of active centres of a series of metal oxide catalysts
(Fe, Ni, Co, Pd) on different metal oxide supports (CeO
2
, ZrO
2
, TiO
2
, SiO
2
, Al
2
O
3
) was done by
in situ FTIR method with use of different probe molecules. Based on the results the IR
vibrations the surface intermediates have been assigned to formats, carbonates on different
active centres. The recognition of methoxy groups on the surface of the working catalyst during
the experiments performed in situ with FTIR detection proved the Langmuir-Hinschelwood
mechanism for methane catalytic combustion.
Keywords: active centres; infrared spectroscopy; probe molecules; metal oxides; methane combustion
Acknowledgment
Financial support for this work was provided by the National Science Centre, Poland – project no.
2013/09/B/ST8/00171.
References
[1] O. Demoulin, M. Navez, P. Ruiz, Appl. Catal. A-Gen. 295 (2005) 59.
[2] M.C. Kung, SS. -Y. Lin, H.H. Kung, Top. Catal. 55 (2012) 108.
[3] M. Schmal, M. Souza, V. Alegre, M. Dasilva, D. Cesar, C. Perez, Catal. Today 118 (2006) 392.
[4] S. Zhang, J. Shan, L. Nie, L. Nguyen, Z. Wud, F. (Feng) Tao, Surf. Sci. 648 (2016) 156.
XIV
h
International Conference on Molecular Spectroscopy, Białka Tatrzańska 2017
263
T3: P–9
Determination of rhodamine 6G (R6G) orientation on SERS-active
hybrid platform consisting of silver nanoparticles and graphene oxide –
relationship between graphene layer thickness
and fluorescence quenching ability
Sylwia Berbeć
1
, and Barbara Pałys
1
1
Department of Chemistry, Biological and Chemical Research Centre, University of Warsaw,
Pasteura 1, 02-093 Warsaw, Poland , e-mail: sberbec@chem.uw.edu.pl
Herein, we have developed a surface enhanced Raman scattering (SERS) active substrate for
R6G based on electrochemically reduced graphene oxide and electrochemically deposited silver
nanostructures. Such a surface hybrid material allowed the detection of organic probe with a
very good precision. Furthermore, the use of partially reduced graphene oxide not only
improved the ability of the surface to adsorb organic molecules but also enabled to suppress the
fluorescence of the probe and thereby enhanced Raman spectral quality [1–3].
We propose a very easy way to reduce silver ions on different surfaces using electrochemical
methods. The great advantage of this approach is the ability to influence the size of structures
created on the surface and the thickness of the layer by changing the parameters of the
experiment (reduction time and potential). To increase the ability of silver ion reduction on the
surface, we modify it with partly reduced graphene oxide and then adsorb ammonia on it.
Because of the presence of structural defects in both graphene oxide and partially reduced
graphene oxide so called ‘hot spots’ appear on the surface that promote the adsorption of
molecules or ions. Increasing the hydrophobic nature of the surface may promote the adsorption
of organic particles by the π- π stacking interaction with the honeycomb lattice of graphene
material. The use of affinity graphene layers for aromatic compounds can also be a great way to
remove such molecules from solutions and help to remove the impurities from the environment
[1–3].
Raman imaging was used to determine the relationship between the amount of immobilized
R6G and the thickness of the graphene layers. It turned out that both the degree of GO reduction
and the thickness of graphene layers affect the intensity of the R6G spectrum, its orientation and
fluorescence [4].
Keywords: Rhodamine 6G, graphene oxide, SERS substrates
References
[1] Ch.Wua, E. Chenb, J. Wei, 506 (2016) 450.
[2] H. Wadhwa, D. Kumar, S. Mahendia , S. Kumar, 194 (2017) 274.
[3] S. Sharma, V.Prakash, S.K. Mehta, 86 (2017) 155.
[4] A.M. Michaels, J. Jiang, and L. B., 104 (2000) 11965.
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