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Physik der Energiewandlung und -speicherung

Aliaksandr Bandarenka

Forschungsgebiet

We conduct research in the area of the physics of energy conversion and storage. The main topics include the design and implementation of functional materials and a better understanding and characterization of electrified interfaces. The material design is based on a bottom-up approach using input from electrochemical surface science and starting from model surfaces.

Adresse/Kontakt

James-Franck-Str. 1
85748 Garching b. München

Mitarbeiterinnen und Mitarbeiter der Arbeitsgruppe

Professorinnen und Professoren

Mitarbeiterinnen und Mitarbeiter

Lehrangebot der Arbeitsgruppe

Lehrveranstaltungen mit Beteiligung der Arbeitsgruppe

Ausgeschriebene Angebote für Abschlussarbeiten an der Arbeitsgruppe

Electrodeposition of Pt-rare earth alloy catalysts for fuel cell vehicles

In proton exchange membrane fuel cells hydrogen is electrochemically oxidized at the negative electrode, while oxygen is reduced at the positive electrode. The oxygen reduction reaction (ORR) is a very sluggish reaction. Therefore rather large overpotentials are associated with this reaction that lower the usable voltage of the cell at a given current and thus the energy conversion efficiency. Large amounts of expensive Pt catalyst are used in commercially available fuel cell vehicles in order to minimize these losses and to increase the power output of the fuel cell. In order to lower the costs and to improve the conversion efficiency, alternative catalysts compared to pure Pt are needed. One extremely attractive group of materials are Pt rare earth alloys [1]. Such alloys have been shown to be several times more active than pure Pt. Also nanoparticles generated in a cluster source have demonstrated very high activities (activity usually is expressed as the oxygen reduction reaction current measured at a certain potential normalized to the total mass of the catalyst in the electrode or to its true surface area) for the oxygen reduction reaction, and do show an excellent stability [2, 3]. However, scalable synthesis methods are required for making these nanoparticles, and this is not that simple as the rare earth elements are very reactive towards moisture and air.

Recently, within two European Projects (see also http://www.inspire-fuelcell.eu/) we have aimed at making Pt-rare earth alloys via electroreduction from ionic liquids [4]. Ionic liquids are basically salts with a melting point below 100°C. Many ionic liquids are even liquid at room temperature. They show a wide electrochemical window permitting the deposition of very reactive metals, have a low vapour pressure and often low toxicity [5]. The electrodeposition of platinum has been successful from some ionic liquids. The electrodeposition of rare earth metal also has been successful from different ionic liquids. First tests on the electrodeposition of Pt in these latter liquids have been carried out.

The task of the current thesis is two-fold: First the electrodeposition of Pt shall be studied in a three component system: Pt chloride salt, an organic chloride as a complexing agent, and the ionic liquid from which the deposition of the rare earth metal was successful. Techniques like the electrochemical quartz crystal microbalance and scanning tunneling microscopy shall be employed to learn more about the electrodeposition mechanisms. The catalytic properties for the ORR shall be determined in aqueous solutions with the rotating disc electrode technique (procedure available). Second, Pt and the rare earth metal shall be deposited in parallel from a mixed electrolyte. The best mixture ratio and the deposition potential need to be chosen carefully to enable alloy deposition and control of its composition.

[1] M. Escudero-Escribano, P. Malacrida, M.H. Hansen, U.G. Vej-Hansen, A. Velázquez-Palenzuela, V. Tripkovic, J. Schiøtz, J. Rossmeisl, I.E.L. Stephens, I. Chorkendorff, Science, 352 (2016) 73-76.

[2] A. Velázquez-Palenzuela, F. Masini, A.F. Pedersen, M. Escudero-Escribano, D. Deiana, P. Malacrida, T.W. Hansen, D. Friebel, A. Nilsson, I.E.L. Stephens, I. Chorkendorff, J. Catal., 328 (2015) 297-307.

[3] P. Hernandez-Fernandez, F. Masini, D.N. McCarthy, C.E. Strebel, D. Friebel, D. Deiana, P. Malacrida, A. Nierhoff, A. Bodin, A.M. Wise, J.H. Nielsen, T.W. Hansen, A. Nilsson, I.E.L. Stephens, I. Chorkendorff, Nat. Chem., 6 (2014) 732–738.

[4] L. Asen, W. Ju, E. Mostafa, S. Martens, U. Heiz, U. Stimming, O. Schneider, ECS Trans., 75 (2016) 323-332.

[5] S. Zein El Abedin, F. Endres, ChemPhysChem, 7 (2006) 58-61.

geeignet als
  • Bachelorarbeit Physik
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Kern-, Teilchen- und Astrophysik
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Aliaksandr Bandarenka
Electrodeposition of refractory metals from ionic liquids

Refractory metals are metals like titanium, tantalum, niobium, tungsten, and molybdenum. They are high-melting reactive metals that in contact with air from a very thin oxide layer that protects them from further oxidation and renders them very stable towards corrosion. This makes them important as coatings for the chemical process industry [1, 2]. Ti and Ta also show excellent biocompatibility and are of interest for implant materials [3, 4]. Therefore, there is a strong interest in generating dense coatings with thicknesses in the µm-mm range of these materials. For other metals, like zinc, nickel, chromium, copper, gold, electroplating is the key technology to make such coatings. Aqueous solutions with suitable additives and well-established deposition conditions are used. The German electroplating industry has an annual turnover of ~ 6 billion €, corresponding to 2% of the gross national product. The created values through e.g. prevention of corrosion damage is much larger, ~ 150 billion €/year. Thus electroplating is a highly important technology impacting everybody’s daily life. Unfortunately, most refractory metals cannot be deposited from aqueous electrolytes. Therefore a new technology needs to be devised. Electrodeposition from ionic liquids is such a technology. Ionic liquids are salts with a melting point below 100°C. Many ionic liquids are even liquid at room temperature. These liquids show a wide electrochemical window permitting the deposition of very reactive metals, have a low vapour pressure and often low toxicity [5]. Most papers studying the deposition of Ti, Ta and Nb so far have been using halide based precursors. While for Ta and Nb some success has been reported [6-9], but films are still not free from cracks and impurities, the deposition of Ti succeeded only in ultrathin films so far [10, 11]. The deposition of W and Mo was successful in the case of alloys but the deposition of the pure materials has not been achieved. Currently, in collaboration with the Chemistry department and several German research institutions, we study more in depth the electrochemical deposition of refractory metals (see www.galactif.de). One approach is to use entirely new metal precursor salts, that are not commercially available, and different ionic liquids. These salts and in part the ionic liquids are prepared by project partners in the Chemistry Department. The current master thesis would be separated into two parts: In the first part, electrolyte solutions made from components provided by the project partner shall be screened using the electrochemical quartz crystal microbalance technique with respect to their potential for electrodeposition. In the second part, one or two systems are selected and studied more in depth, to understand the physical details of the electrodeposition mechanism, to characterize the electrodeposited layers structurally and with respect to their corrosion properties. [1] U. Gramberg, M. Renner, H. Diekmann, Mater. Corros., 46 (1995) 689-700. [2] M. Schussler, Int. J. Refract. Hard Met., 2 (1983) 67-70. [3] J.R. Vargas, S. Seelman, in, Zimmer, Inc., USA . 2014, pp. 17pp. [4] V.-H. Pham, S.-H. Lee, Y. Li, H.-E. Kim, K.-H. Shin, Y.-H. Koh, Thin Solid Films, 536 (2013) 269-274. [5] S. Zein El Abedin, F. Endres, ChemPhysChem, 7 (2006) 58-61. [6] T. Carstens, A. Ispas, N. Borisenko, R. Atkin, A. Bund, F. Endres, Electrochimica Acta, 197 (2016) 374-387. [7] P. Giridhar, S. Zein El Abedin, A. Bund, A. Ispas, F. Endres, Electrochimica Acta, 129 (2014) 312-317. [8] S. Krischok, A. Ispas, A. Zühlsdorff, A. Ulbrich, A. Bund, F. Endres, ECS Transactions, 50 (2013) 229-237. [9] N. Borisenko, A. Ispas, E. Zschippang, Q. Liu, S. Zein El Abedin, A. Bund, F. Endres, Electrochimica Acta, 54 (2009) 1519-1528. [10] F. Endres, S. Zein El Abedin, A.Y. Saad, E.M. Moustafa, N. Borissenko, W.E. Price, G.G. Wallace, D.R. MacFarlane, P.J. Newman, A. Bund, Physical Chemistry Chemical Physics, 10 (2008) 2189-2199. [11] C.A. Berger, M. Arkhipova, A. Farkas, G. Maas, T. Jacob, Physical Chemistry Chemical Physics, 18 (2016) 4961-4965.


geeignet als
  • Masterarbeit Physik der kondensierten Materie
  • Masterarbeit Applied and Engineering Physics
Themensteller(in): Aliaksandr Bandarenka

Abgeschlossene und laufende Abschlussarbeiten an der Arbeitsgruppe

Identification of active electrocatalytic centres using electrochemical scanning tunneling microscopy
Abschlussarbeit im Masterstudiengang Physics (Applied and Engineering Physics)
Themensteller(in): Aliaksandr Bandarenka
Investigation of Transport Properties of Lithium in Electrode Materials
Abschlussarbeit im Masterstudiengang Physics (Applied and Engineering Physics)
Themensteller(in): Aliaksandr Bandarenka
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