Role within strategic research plan of Helmholtz Centers
Our research goals are inter-coordinated with a master research programme dedicated to energy – materials science, which is defined and detailed within the POF III.
The key contributions from the EM-IMM Institute are
- Photo- and electrochemical electron and
- structural dynamics in molecular and solid functional catalysis
We are developing laser-based, tabletop, transient spectroscopies, employing ultrafast laser pulses in the UV-VIS and XUV energy range. These methods allow us to investigate light-induced molecular processes in catalysts and functional materials on the natural time scale of chemical reactions. Specific projects include the investigations of:
- Electron injection kinetics in dye-sensitized solar cells, for example the roles of interfacial complexes in the electron transfer processes occurring at the N3/ZnO dye-semiconductor interface.
- Spin crossover mechanisms in metal coordination complexes, for example probing the role of triplet transient states in the singlet-to-quintet spin crossover process in iron(II)tris(bipyridine).
- The charge-transport mechanisms responsible for water splitting, for example by photoexcited carbon-nitride polymers.
- Emission of solvated electrons from diamond nanoparticles in water and/or ionic liquids responsible for CO2 photoreduction.
In parallel, we aim to extend our photon energy range into the soft X-ray spectrum and to improve our time resolution from >50 fs to 15 fs or less, allowing us to probe such processes with reaction site-specificity and to unravel further details of ultrafast photoreaction mechanisms.
The infrared group is focusing on the investigation of new functional materials particularly those of importance to renewable energy sources and light driven water oxidation as well as electro-catalysis. Our interest is to understand, at the molecular level, what is responsible for the stability and efficiency of such processes by following the interplay and the dynamics of the ionomer-catalysts systems using state-of-the-art synchrotron high spatial resolution, in operando and time resolved THz and infrared methods.
To pursue this we develop synchrotron methods in far infrared/THz regions to systematically study the interaction of multiply charged cations with the ionomer matrix under different environmental conditions.
Furthermore we are developing in operando ATR based electrochemical cells to directly follow the reactions responsible for the efficiency of the catalysts based water splitting techniques, for example the electrochemical formation of the MnOx nanoparticles from a range of catalyst precursors.
We will be able to follow the kinetics in the microsecond time scale of catalytic reactions using a broadband, single-shot infrared set up we are developing. We intend to use this unique spectrometer to also follow non cyclic systems with completely irreversible reaction pathways, like rhodopsin, or systems that require a long time span to recover to the initial states such as that seen in the light-gated channelrhodopsin.
We develop methods using Soft X-ray spectroscopy to characterize electronic structure and ultrafast relaxation processes occurring in solids, liquids and interfaces. The major milestones of our research are:
The measurement of the surface potential of nanoparticles (NP) in aqueous solution. Our focus is on TiO2, Fe2O3, Fe3O4, and diamond NPs, and the effect of pH and co-solutes. Along with the full characterization of the NP–water interfacial structure we provide the basis for understanding chemical reactions at the molecular level at these catalytically active systems.
The identification of the chemical reactions initiated by the transient reactive species formed by the ultrafast relaxation of the X-ray excited/ionized intermediates. We hereby explore non-local electronic relaxation processes which help us understand the complex electronic-structure interactions, for instance at the solid–water interface. This contributes to a better understanding of the chemical reactions in photo- or electrochemical cells (see next points).
The understanding of the catalytic mechanism and improvement of the catalytic efficiency of manganese oxides (MnOx) as water-oxidation catalysts. We study the electronic structure of various MnOx catalysts by X-ray and infrared spectroscopies, as well as by theory, in order to develop high-efficient catalysts for water splitting.
The understanding of the metalloporphyrin functions in liquid environments. We carry out in-situ investigations of various metalloporphyrins dissolved in solutions by soft X-ray spectroscopy, focusing on the local electronic structure of the metal centers and their closely coordinated ligands. We aim to actively tune the porphyrin functionality by modifying the local electronic structure.