Dipl.-Phys. | Free University Berlin (1998) |
Dr. rer. nat. | Institut für Experimentalphysik, Free University Berlin (1999-2003) |
Postdoc | Max Planck Institute for Bioinorganic Chemistry; today: MPI CEC (2004-2005) |
Postdoc | Helmholtz Zentrum Berlin für Materialien und Energie (HZB) (2006-2013) |
Staff Scientist | HZB's EPR lab (2013-2018) |
Adjunct Professor | Monash University, Melbourne, Australia (since 2016) |
Research group leader | MPI CEC (since 2018) |
The EPR Research Group at MPI CEC employs electron paramagnetic resonance (EPR) spectroscopy to identify and characterise paramagnetic states relevant to energy conversion and storage processes. Special focus is devoted to catalytically active transition-metals and main group compounds as well as organic radicals. We develop and utilise state-of-the-art EPR spectrometers ranging from GHz to THz frequencies. Our spectrometers are capable of a wide repertoire of CW/pulsed multi-resonance and multi-frequency EPR methods for powder, crystal, solution and in-situ experiments.
Currently we are working in the following fields of research:
An understanding of catalyst function enables rational modification and improvement. Yet, the most reactive and catalytically active states are typically only formed under operational conditions. This motivates our group to develop methodology for in situ / operando studies that allow EPR characterisation of catalysts for energy conversion reactions. These studies require electrochemical measurements to be undertaken within the constraints of specific spectroscopic equipment, which we design and develop to ensure the conditions of analysis are truly relevant to the operational catalytic activity.
The applicability of EPR to any electrochemically derived/analysed species is that single electron redox steps frequently involve paramagnetic states. The exceptional sensitivity of spectro-electrochemical EPR (SEC EPR) to these states makes it powerful in examining the subtle, yet crucial, electronic effects that enable catalysis. EPR also allows selective analysis of paramagnetic oxidation states independent of diamagnetic species, thus providing selectivity that is unavailable with many other techniques - especially if the catalyst ground state is diamagnetic. In-situ EPR spectra are interpreted with extensive experiment-simulation comparisons and then correlated with catalytic measurements as well as with results from other techniques. SEC EPR is employed within DFG collaborative research centre (CRC) 247 for studies in paramagnetic states in Co oxide catalysts for alcohol oxidation reactions and within CRC 1487 for the characterization of high spin iron states in single atom catalysts for the oxygen reduction reactions.
Bonke, S. A.; Risse, T.; Schnegg, A.; Brückner, A. (2021) In situ electron paramagnetic resonance spectroscopy for catalysis. Nature Review Methods Primers, https://doi.org/10.1038/s43586-021-00031-4
Contact: Dr. Kaltum Abdiaziz
EPR characterisation of mono- and multi-nuclear high-spin states (electron spin, S > 1/2) in transition-metal ions targets the determination of their spin coupling parameters, in particular zero-field splittings and exchange couplings. The latter are sensitive probes of the metal ion’s coordination environment and electronic structure. In the case of a catalytically active ion, spin couplings provide unique information on its structure-function relationship. However, the highly desired spin couplings are oftentimes not accessible with standard 9.5 GHz EPR spectrometers. To bridge this gap we develop and apply advanced field and frequency domain EPR methods, covering the GHz to THz EPR-excitation energy range.
Lohmiller, T.; Spyra, C.-J.; Dechert, S.; Demeshko, S.; Bill, E.; Schnegg, A.; Meyer, F. (2022) Antisymmetric Spin Exchange in a μ-1,2-Peroxodicopper(II) Complex with an Orthogonal Cu–O–O–Cu Arrangement and S = 1 Spin Ground State Characterized by THz-EPR. JACS Au, https://doi.org/10.1021/jacsau.2c00139
Contact: Dr. Alexander Schnegg
EPRoC are mm-sized sensors that incorporate a microwave source and detector on a surface array allowing for a fundamental paradigm shift in EPR spectroscopy by facilitating in situ measurements of paramagnetic samples in miniaturized setups in a cost-efficient way. We are interested in integrating the EPRoC sensors, designed in the Anders Group (Universität Stuttgart), in an electrode for electrochemical experiments, alongside the characterization of paramagnetic states in liquid solutions, e.g. in electrochemical cells, batteries or reactors. Research with EPRoC sensors is funded by the Federal Ministry of Education and Research (Grant reference number: 03SF0565A).
Contact: Dr. Takuma Sato
The identification and characterization of catalytically active sites occupy a central place in the study of catalysis. As the active sites often involve paramagnetic states, EPR spectroscopy is the method of choice to obtain exquisite details on their geometric and electronic structure. In our group, high-resolution multi-frequency (S-, X-, Q- and W-band) and multi-resonance EPR techniques are employed to provide such functional information in the different branches of catalysis ranging from homogenous, heterogeneous and single-site heterogeneous catalysis. By using hyperfine spectroscopies (HYSCORE, ENDOR and EDNMR) we monitor the nuclear spins from the first and second coordination sphere of the paramagnetic active sites. This allows us to shed light on the intimate features of the chemical bonding, which is crucial to understand the catalytic potential of active species. The calculation of the EPR parameters with state-of-the-art electronic structure quantum chemical methods translates the spectroscopic findings into microscopic structure of the catalyst's active site enabling structure–property correlations.
Yang, X.; Reijerse, E. J.; Bhattacharyya, K.; Leutzsch, M.; Kochius, M.; Nöthling, N.; Busch, J.; Schnegg, A.; Auer, A. A.; Cornella, J. (2022) Radical Activation of N–H and O–H Bonds at Bismuth(II). Journal of the American Chemical Society, https://doi.org/10.1021/jacs.2c05882
Lin, Y.-H.; Kutin, Y.; van Gastel, M.; Bill, E.; Schnegg, A.; Ye, S.; Lee, W.-Z. (2020) A Manganese(IV)-Hydroperoxo Intermediate Generated by Protonation of the Corresponding Manganese(III)-Superoxo Complex. Journal of the American Chemical Society, https://doi.org/10.1021/jacs.0c02756
Contact: Dr. Edward J. Reijerse and Dr. Paolo Cleto Bruzzese