THEORY DEPARTMENT
Fritz Haber Institute of the Max Planck Society

All FHI Seminars

Single-molecule chemistry via noncontact atomic force microscopy: ultrahigh resolution imaging and tip-induced switching
Speaker:Dr. Akitoshi Shiotari
 University of Tokyo
Time:Wednesday, 26th February 2020, 11:00 AM
Location: PC Seminar Room G2.06, Building G
Organized: PC
Abstract: Single-molecule chemistry [1] has progressed together with the development of scanning probe microscopy and its related methods. Scanning tunneling microscopy (STM) has been widely used for the observation and control of configurational changes and reactions for individual molecules on surfaces. As a complemental method, noncontact atomic force microscopy (ncAFM) also provides superior insights into chemistry at the single-atom/molecule level; ncAFM with a molecule/atom-functionalized tips visualizes atomic structures of organic molecules [2], and interatomic force measurements clarify the mechanisms of tip-induced configurational changes [3]. With ncAFM, we demonstrated ultrahigh spatial resolution imaging of on-surface-synthesized organic molecules [4] and hydrogen-bonding networks of water monolayers [5]. Furthermore, we established an “ON-OFF-ON” toggle switch of a single nitric oxide molecule, which can be controlled by functionalized tips [6]. In this talk, I report on these ncAFM studies and a recent study of chemical reaction of a single molecule induced by a metal tip. [1] W. Ho, J. Chem. Phys. 117, 11033 (2002) [2] L. Gross et al., Science 325, 1110 (2009). [3] J. N. Ladenthin et al., Nat. Chem. 8, 935 (2016). [4] A. Shiotari and Y. Sugimoto, Nat. Commun. 8, 16089 (2017). [5] A. Shiotari et al., Nat. Commun. 8, 14313 (2017). [6] A. Shiotari, T. Odani, and Y. Sugimto, Phys. Rev. Lett. 121, 116101 (2018).

Computational modelling of catalytic nanomaterials - as simple as possible, but not simpler
Speaker: Prof. Konstantin Neyman
 ICREA Dept. de Ciència dels Materials i Química Física & Inst. de Química Teòrica i Computacional Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
Time:Tuesday, 17th March 2020, 11:00 AM
Location: Seminar Room Building P, Faradayweg 16, 14195 Berlin
Organized: GFW
Abstract: Active metal components are commonly present in catalysts as nanoparticles containing thousands atoms. Due to their sizes, the particles are inaccessible for density-functional calculations. Yet, they can be quite realistically represented by computationally tractable smaller model metal particles of 100-200 atoms, whose surface sites marginally change the reactivity with increasing particle size. These models expose active sites, whose structure, geometric flexibility and reactivity match those of the sites in customary catalysts. We designed and used such models to computationally describe different monometallic [1,2] and bimetallic [3,4] particles in catalytic materials. Moreover, calculations of model metal particles supported on regular (see Figure) and nanostructured surfaces allow delineating elusive interface effects on the structure and reactivity of the catalysts [5-10]. The effects identified and quantified using our modelling will be discussed in relation with the experimental observations of our co-authors. Figure. Pt95 and Pt122 particles forming {100}/(111) and {111}/(111) interfaces with CeO2(111) support [8,9]. References: 1. F. Viñes, C. Loschen, F. Illas, K.M. Neyman. Edge sites as a gate for subsurface carbon in palladium nanoparticles. J. Catal. 266 (2009) 59 2. H.A. Aleksandrov, S.M. Kozlov, S. Schauermann, G.N. Vayssilov, K.M. Neyman. How absorbed hydrogen affects catalytic activity of transition metals. Angew. Chem. Int. Ed. 53 (2014) 13371 3. S.M. Kozlov, G. Kovács, R. Ferrando, K.M. Neyman. How to determine accurate chemical ordering in several nanometer large bimetallic crystallites from electronic structure calculations. Chem. Sci. 6 (2015) 3868 4. L. Vega, H.A. Aleksandrov, K.M. Neyman. Using density functional calculations to elucidate atomic ordering of Pd-Rh nanoparticles at sizes relevant for catalytic applications. Chin. J. Catal. 40 (2019) 1749 and references therein 5. G.N. Vayssilov, Y. Lykhach, A. Bruix, F. Illas, K.M. Neyman, J. Libuda et al. Support nanostructure boosts oxygen transfer to catalytically active platinum nanoparticles. Nature Mater. 10 (2011) 310 6. A. Bruix, Y. Lykhach, V. Matolín, J. Libuda, K. M. Neyman et al. Maximum noble metal efficiency in catalytic materials. Angew. Chem. Int. Ed. 53 (2014) 10525 7. S.M. Kozlov, H.A. Aleksandrov, K.M. Neyman. Energetic stability of absorbed H in Pd and Pt nanoparticles in a more realistic environment. J. Phys. Chem. C 119 (2015) 5180 8. Y. Lykhach, S.M. Kozlov, V. Matolín, K.M. Neyman, J. Libuda et al. Counting electrons on supported nanoparticles. Nature Mater. 15 (2016) 284 9. S.M. Kozlov, K.M. Neyman. Effects of electron transfer in model catalyst composed of Pt nanoparticles on CeO2(111) surface. J. Catal. 344 (2016) 507 10.Y. Suchorski, S.M. Kozlov, K.M. Neyman, G. Rupprechter et al. The role of metal/oxide interfaces for long-range metal particle activation during CO oxidation. Nature Mater. 17 (2018) 519

Lab-Based X-Ray Photoelectron Spectroscopy for Tapping into Potential Developments at Liquid/Solid Interfaces
Speaker: Prof. Sefik Süzer
 Department of Chemistry, Bilkent University, 06800 Ankara, Turkey
Time:Friday, 20th March 2020, 1:30 PM
Location: Haber-Villa
Organized: CP
Abstract: Nonvolatile room temperature ionic liquid (RTIL) electrolytes have allowed us and others to utilize lab-based XPS instruments for investigating various electrochemical processes under ultrahigh vacuum conditions, without the need for extensive pumping techniques nor synchrotron facilities. In this contribution, we report on using a similar multi-layered graphene as the top electrode and utilize XPS to monitor in-situ; (i) changes in the anion/cation intensity ratio under applied electric fields and (ii) potential developments on different surface structures, which are derived from the shifts in the binding energies of the corresponding atomic core levels in a chemically resolved fashion.[1-3] In addition, we will describe Impedance-like XPS Analysis of the Electrowetting Phenomenon, widely used in microfluidics, lab-on-chip, etc.[4-7] Literature: [1] Camci, M.; Aydogan, P.; Ulgut, B.; Kocabas, C.; Suzer, S., Phys. Chem. Chem. Phys. 2016, 18, 28434-28440. [2] Camci, M. T.; Ulgut, B.; Kocabas, C.; Suzer, S., ACS Omega 2017, 2, 478-486. [3] Camci, M. T.; Ulgut, B.; Kocabas, C.; Suzer, S., J. Phys. Chem. C 2018, 122, 11883-11889. [4] Mugele, F.; Heikenfeld, J. Electrowetting: Fundamental Principles and Practical Applications. 2019, Wiley-VCH, Weinheim, Germany. [5] Aydogan Gokturk, P.; Ulgut, B.; Suzer, S. DC Electrowetting of a nonaqueous liquid revisited by XPS. Langmuir 2018, 34, 7301-7308. [6] Aydogan Gokturk, P.; Ulgut, B.; Suzer, S. AC Electrowetting Modulation of Low Volatile Liquids Probed by XPS: Dipolar vs. Ionic Screening. Langmuir 2019, 35, 3319-33326. [7]Uzundal, C.B.; Sahin, S.; Aydogan Gokturk, P.; Wu, H.; Mugele, F.; Ulgut, B.; Suzer, S. Langmuir 2019, 35,16989−16999.

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