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This collaborative project between two scientific disciplines at Technische Universität München - technical chemistry and semiconductor physics - aims at combining expertise in catalytic conversion of complex model substrates with semiconductor physics and technology to explore the possibilities and limitations of the electronic control and monitoring of a prototypical catalyzed reaction. The long term goal is to use this knowledge to develop new electrochemically stimulated materials for catalytic conversions, potentially in “lab on a chip” or integrated microreactor applications. The catalysts are prepared on single crystal supports of GaN layers of different doping and chemical surface termination. The rationale behind the use of semiconducting supports is their unique possibility to (i) actively control the density and type of charge carriers at the surface via doping, illumination, and/or the field effect, and (ii) to detect reaction-mediated changes of the surface potential with a high sensitivity. Pt nanoparticles are used as model catalysts offering a variety of particle sizes, shapes and coverages, using deposition by thermal evaporation or by spincoating chemically synthesized nanoparticle solutions. The nanoparticle deposition is optimized regarding coverage and distribution homogeneity. The role of the particle size and geometry is explored. The nanoparticle size and geometry, defined by the synthesis method, are characterized by Transmission Electron Microscopy (TEM), while the morphology of the formed hybrid structures after deposition is characterized by Scanning Probe Microscopy (AFM) [1]. The chemical composition of the surfaces is investigated by Thermal Desorption Spectroscopy (TDS) and X-ray Photoelectron Spectroscopy (XPS). Electrical characterization is performed by electrochemical analysis such as cyclic voltammetry, and transient photocurrent measurements [2, 3]. One major challenge is the small total amount of catalyst material on the investigated model surfaces. Thus, for a detailed investigation, advanced light source user facilities like the electron storage ring BESSY II or the Advanced Light Source of Argonne National Lab are required. Combined Temperature Programmed Reaction (TPRx), Grazing Incidence Small-Angle X-ray Scattering (GISAXS), and X-ray Absorption Spectroscopy (GIXAS) was employed to study particle size, shape, and particle stability under reaction conditions [4]. In-situ high-pressure XPS was utilized to characterize the chemical and electronic surface properties under reaction conditions [5].

The catalytic activity of metal particles immobilized on the semiconducting surfaces was investigated for the hydrogenation of ethene to ethane. A suitable microstructured reactor was developed which was integrated into an external recycle loop. That approach gave the possibility to achieve significant catalyst activity and therefore reaction kinetics can be studied. The proposed benefit of our project is the first-time possibility to study complex catalytic reactions under such well controlled conditions including electrochemical stimuli.

 

Figure 1 Pt nanoparticle/ n-type GaN hybrid structure under UV illumination: Photo-induced, interfacial charge transfer alters the affinity of the Pt nanoparticles to electronegative species like oxygen atoms (left). The charge transfer mechanism is understood from the corresponding band alignment providing free charge carriers at the interface (right).

[1] S. Schäfer, S. A. Wyrzgol, Y. Wang, J. A. Lercher, M. Stutzmann, Platinum nanoparticles deposited on wide-bandgap semiconductor surfaces for catalytic applications, Phys. Stat. Sol. C 7, 2 (2010), 411-414

[2] S. Schäfer, A.H.R. Koch, A. Cavallini, M. Stutzmann, and I.D. Sharp, Charge transfer across the n-Type GaN-electrolyte interface, J. Phys. Chem. C 116, 22281 (2012)

[3] S. Schäfer, S.A. Wyrzgol, J.A. Lercher, M. Stutzmann, and I.D. Sharp, Charge transfer across the GaN/Pt nanoparticle interface in electrolyte, ChemCatChem, accepted (2013)

[4] S. A. Wyrzgol, S. Schäfer, S. Lee, B. Lee, M. Di Vece, X. Li, S. Seifert, R. E. Winans, M. Stutzmann, J. A. Lercher, S. Vajda, Combined TPRX, in situ GISAXS and GIXAS studies of model semiconductor-supported platinum catalysts in the hydrogenation of ethane, Phys. Chem. Chem. Phys. 12, (2010), 5585-5595

[5] S. Schäfer, S.A. Wyrzgol, R. Caterino, A. Jentys, S.J. Schoell, M. Hävecker, A. Knop-Gericke, J.A. Lercher, I.D. Sharp, and M. Stutzmann, Platinum Nanoparticles on Gallium Nitride Surfaces: Effect of Semiconductor Doping on Nanoparticle Reactivity, J. Am. Chem. Soc. 134, 12528 (2012)

01-01-1970
14.02.17

Registration now open: IGSSE Forum 2017

29-31 May 2017, TUM Science and Study Center Raitenhaslach, Burghausen

25.04.17

EuroTech postdoc workshop: Success in academia?

20-22 September 2017, Technical University of Denmark, Lynby Campus

18.04.17

Project team ROLITOS in a German documentary

10 May 2017, 11.30 pm Suedwestrundfunk (TV)

30 May 2017, 10.30 pm Bayerischer Rundfunk (TV)

11.04.17

Apply now: McKinsey 'Forschergeist' symposium

9-11 June 2017, Berlin

For doctoral researchers and postdocs!

10.04.17

Register now: ICMSB 2017

26-28 July 2017, TUM Study and Science Center, Raitenhaslach

14.02.17

Registration now open: IGSSE Forum 2017

29-31 May 2017, TUM Science and Study Center Raitenhaslach, Burghausen

05.06.16

10th IGSSE Forum

Smart cooperation - science and technology in, with and for society

15.12.15

The Science of Cooking

Doctoral Candidates explore the Secrets of a great Dinner

26.11.15

ATUMS@IGSSE

Having heard of a great Canadian Kick-Off Meeting, everyone at IGSSE was thrilled to welcome the...

20.11.15

Breakfast at IGSSE´s

Meet the IGSSE team every other month! All the things IGSSE members wanted to asked but never dared...

13.10.15

Save the Date: Canadian ATUMS Speaker on "Global Science- Global Career"

26. November 2015, 6-8 pm, IAS Faculty Club, Garching Campus

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Monday, 03. April 2017
1st ExaHyPE Colloquium
3 April 2017, 1pm-5pm, Leibniz Supercomputing Centre, Garching Campus