Philipp Myrach
Max Planck Society
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Featured researches published by Philipp Myrach.
Chemcatchem | 2010
Philipp Myrach; Niklas Nilius; Sergey V. Levchenko; Anastasia Gonchar; Thomas Risse; Klaus-Peter Dinse; L. A. Boatner; Wiebke Frandsen; Raimund Horn; Hans-Joachim Freund; Robert Schlögl; Matthias Scheffler
Li‐doped MgO is a potential catalyst for the oxidative coupling of methane, whereby surface Li+ O− centers are suggested to be the chemically active species. To elucidate the role of Li in the MgO matrix, two model systems are prepared and their morphological, optical and magnetic properties as a function of Li doping are investigated. The first is an MgO film deposited on Mo(001) and doped with various amounts of Li, whereas the second is a powder sample fabricated by calcination of Li and Mg precursors in an oxygen atmosphere. Scanning tunneling and transmission electron microscopy are performed to characterize the morphology of both samples. At temperatures above 700 K, Li starts segregating towards the surface and forms irregular Li‐rich oxide patches. Above 1050 K, Li desorbs from the MgO surface, leaving behind a characteristic defect pattern. Traces of Li also dissolve into the MgO, as concluded from a distinct optical signature that is absent in the pristine oxide. No electron paramagnetic resonance signal that would be compatible with Li+O− centers is detected in the two Li/MgO samples. Density‐functional theory calculations are used to determine the thermodynamic stability of various Li‐induced defects in the MgO. The calculations clarify the driving forces for Li segregation towards the MgO surface, but also rationalize the absence of Li+O− centers. From the combination of experimental and theoretical results, a detailed picture arises on the role of Li for the MgO properties, which can be used as a starting point to analyze the chemical behavior of the doped oxide in future.
Journal of the American Chemical Society | 2010
Xiao Lin; Bing Yang; Hadj-Mohamed Benia; Philipp Myrach; Maxim Yulikov; Andreas Aumer; Matthew A. Brown; Martin Sterrer; Oleksander Bondarchuk; Esther Kieseritzky; Jan Rocker; Thomas Risse; Hong-Jun Gao; Niklas Nilius; Hans-Joachim Freund
The CO binding behavior to gold particles supported on MgO thin films has been analyzed with scanning tunneling microscopy (STM) and infrared spectroscopy (IRAS). The ad-particles accommodate excess electrons that originate either from a charge transfer through the thin oxide film or from a local interaction with electron-rich oxide defects that act as Au nucleation centers. The enhanced electron density in the Au aggregates affects both the spatial distribution and the vibrational properties of adsorbed CO species. Whereas preferential CO attachment to the chemically unsaturated and electron-rich boundary sites of the Au islands is deduced from the STM data, a continuous downshift of the CO stretching frequency with decreasing particle size is observed in IRAS. Both results are interpreted in the light of CO adsorption to negatively charged metal aggregates and used to draw general conclusions on the interplay between charge and adsorption properties of confined metal systems.
Physical Review B | 2010
Hadj-Mohamed Benia; Philipp Myrach; Anastasia Gonchar; Thomas Risse; Niklas Nilius; Hans-Joachim Freund
Journal of Physical Chemistry C | 2011
Xiang Shao; Philipp Myrach; Niklas Nilius; Hans-Joachim Freund
Physical Review B | 2011
Xiang Shao; Niklas Nilius; Philipp Myrach; Hans-Joachim Freund; Umberto Martinez; Stefano Prada; Livia Giordano; Gianfranco Pacchioni
Physical Review B | 2011
Stefania Benedetti; Philipp Myrach; Alessandro di Bona; S. Valeri; Niklas Nilius; Hans-Joachim Freund
Physical Review B | 2011
Philipp Myrach; Niklas Nilius; Hans-Joachim Freund
Physical Review B | 2012
Niklas Nilius; Stefania Benedetti; Yi Pan; Philipp Myrach; Claudine Noguera; Livia Giordano; Jacek Goniakowski
Journal of Physical Chemistry C | 2011
Stefania Benedetti; Niklas Nilius; Philipp Myrach; Ilaria Valenti; Hans-Joachim Freund; S. Valeri
Journal of Physical Chemistry C | 2009
Philipp Myrach; Niklas Nilius; Hans-Joachim Freund