Description
Poster Session I
The metal-organic frameworks (MOF) are a new class of porous materials that have high potential for carbon capture and storage (CCS). CPO-27-Mg (Mg-MOF-74) is one such MOF that has under-coordinated Mg2+ sites where $\mathrm{CO}_2$ gas molecules can bind selectively at low partial pressure (below 1 bar). Prerequisite to a rational design of improved material with optimized separation...
Ceria ($\mathrm{CeO}_2$) was recently identified as a promising catalyst in the selective hydrogenation of alkynes to alkenes[1]. This reaction occurs primarily on highly dispersed metal catalysts, such as Pd, but rarely on oxide surfaces. The origin of the outstanding activity and selectivity observed on $\mathrm{CeO}_2$ remains unclear. In this work, we show that one key aspect of the...
The combination of mass spectrometry (MS) and infrared (IR) spectroscopy is a powerful tool to elucidate the structure of isolated ions in the unique clean-room environment of the gas-phase. To avoid line broadening due to thermal contributions during the measurement, cryogenic ion spectroscopy can be employed. In our experimental setup we use helium nanodroplets as a matrix to cool ions to...
X-ray absorption near-edge structure (XANES) spectroscopy is a widely used tool to determine structural, chemical, and electronic properties of finite and crystalline systems alike. Due to the localization of the excited core states, XANES is an element- and site-specific probe of the electronic environment of the absorbing atom. Complementing these experiments with accurate first-principles...
The Hydrogen Evolution and Oxidation Reactions (HER/HOR) on Pt have been studied for decades due to their fundamental interest and importance in applications such as electrolyzers and fuel cells. Despite much effort there is no clear view of the mechanism of these reactions that can explain the large dependence of their rates on surface structure, pH and electrolyte. Because the HER/HOR on Pt...
In the past few years, organic-inorganic metal halide perovskites employed as light absorber have achieved an impressive breakthrough in the field of photovoltaics, particularly due to a rapid improvement of the power conversion efficiencies of up to 22 % obtained from perovskite-based solar cells. However, perovskite solar cells are confronted with air stability and reproducibility issues,...
The interest in transition-metal dichalcogenides (TMDs) monolayers
as promising materials for opto-electronics has rapidly increased in the
last few years [1]. The majority of studies has been devoted so far to
group-VI TMDs, with MoS$_\mathrm{2}$ and WS$_\mathrm{2}$ as the most relevant examples
of this material class [1]. Here, we study monolayers of group-IV TMDs
focusing on...
A molecular-level understanding of enantioselective processes on chirally modified surfaces is an important prerequisite for the rational design of new enantiospecific catalysts. Therefore, in this study, the reaction mechanisms, kinetics and dynamics of surface reactions were investigated using multi-molecular beam techniques and in-situ surface spectroscopic and microscopic tools on...
The deposition and annealing of Tb on Si surfaces leads to a variety of fascinating nanostructures from zero-dimensional clusters on Si(111) over one-dimensional nanowires on Si(001) to well ordered two- and three-dimensional Tb silicide layers on Si(111). The metallic Tb disilide monolayer on Si(111) is especially interesting since its formation pins the Fermi level near the Si conduction...
Vibrational action spectroscopy employing infrared radiation from a free electron laser is successfully used since many years for the vibrational and structural characterization of gas phase aggregates. Despite the high sensitivity of this method, no relevant studies have yet been conducted for solid samples. An ultra-high vacuum (UHV), chamber incorporating surface science techniques, has...
Understanding how adsorbates bind to and behave on metal substrates is crucial for advancements in heterogenous catalysis. Ultrashort laser pulses open up new ways to investigate such systems and may also allow for future applications (so-called femtochemistry).
We employ two potential energy surfaces, that were recently developed for the well-known model systems CO on Ru(0001) and CO on...
Advances in generating intense unipolar half-cycle pulses have led to their use in efficient schemes to align and orient molecules as well as to engineer non-equilibrium states of matter. Herein we present preliminary results of a combined analytical and numerical study on the interactions of a 3D rigid rotor with half-cycle pulses efficiently modelled as narrow-width Gaussians. The added...
In this work the Cu/Zn order-disorder transition in Cu$_2$ZnSnS$_4$ kesterites on Wyckoff positions 2c and 2d was investigated by a structural and electronic analysis in theory and experiment. For experimental investigations stoichiometric samples with different Cu/Zn order, annealed in the temperature range of 473-623 K and afterwards quenched, were used. The optical gaps were determined...
Understanding water interactions with metal oxide surfaces [1] (such as aluminum oxide, Al$_\mathrm{2}$O$_\mathrm{3}$) is of importance both for fundamental reasons and for technological applications.
To unravel the details of such interactions, spectroscopic methods in the form of vibrational (IR) spectroscopy or, as surface-sensitive tool, Vibrational Sum Frequency (VSF) generation...
