A5067026810- Electrocatalysts for Energy Conversion
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Electrochemical Analysis and Applications
- Photosynthetic Processes and Mechanisms
- Metal-Catalyzed Oxygenation Mechanisms
- Metalloenzymes and iron-sulfur proteins
- Radiopharmaceutical Chemistry and Applications
- Advanced battery technologies research
- Iron oxide chemistry and applications
- Metal complexes synthesis and properties
- Medical Imaging and Pathology Studies
- Organometallic Complex Synthesis and Catalysis
- CO2 Reduction Techniques and Catalysts
- Advanced Photocatalysis Techniques
- Porphyrin and Phthalocyanine Chemistry
- Radioactive element chemistry and processing
- Geochemistry and Elemental Analysis
- Electrochemical sensors and biosensors
- Magnetism in coordination complexes
- Inorganic Chemistry and Materials
- Copper-based nanomaterials and applications
- Catalytic Processes in Materials Science
- Crystallography and molecular interactions
- Microbial Fuel Cells and Bioremediation
University of Freiburg
2014-2024
Materials Research Center
2024
Janssen (Belgium)
2023
RWTH Aachen University
2023
Modern Electron (United States)
2023
University Medical Center Freiburg
2014-2022
Robert Bosch (Germany)
2021
University of Göttingen
2020
Institut Kurz
2020
FZI Research Center for Information Technology
2018-2019
Biomimetic and efficient: Mixed calcium manganese(III) oxides (see structure; Ca green, Mn red, O white) with elemental compositions structures mimicking the active site of photosystem II were found to be highly catalysts for oxidation water molecular oxygen. As PS II, presence Ca2+ greatly enhances catalyst performance in comparison related manganese-only system Mn2O3. Detailed facts importance specialist readers are published as "Supporting Information". Such documents peer-reviewed, but...
In the worldwide search for sustainable energy technologies, water oxidation by abundant low-cost materials is of key importance. nature, this process efficiently catalyzed an intricate manganese–calcium (Mn4Ca) complex bound to proteins photosystem II (PSII). Recently synthetic oxides were found be active catalysts but at atomic level their structure has remained elusive. To investigate these amorphous catalysts, extended-range X-ray absorption spectroscopy (XAS) K-edges both manganese and...
In reaction sequences for light driven water-splitting into H2 and O2, water-oxidation is a crucial step. vivo, the process catalysed within photoenzyme called photosystem II (PSII) by μ-oxido CaMn4 cluster, oxygen-evolving complex (OEC). The OEC known to be virtually inactive if Ca2+ removed from its structure. Activity can restored not only addition of but also Sr2+ ions. We have recently introduced layered calcium manganese oxides birnessite mineral family as functional synthetic model...
Abstract Two series of complexes [MX(diimine)(CO) 3 ] (M = Tc, Re) have been prepared, fully characterised and investigated for their ability to act as photocatalysts the reduction CO 2 CO. One consists with different aromatic diimine ligands while keeping X Br – constant. The second describes 2,2‐bipyridine variations in anionic ligand . Although numerous this type prepared before, a systematic study photocatalytic activity has not yet carried out. Electrochemical spectroscopic...
Layered manganese oxides from the birnessite mineral family have been identified as promising heterogeneous compounds for water-oxidation catalysis (WOC), a key reaction conversion of renewable energy into storable fuels. High catalytic rates were especially observed birnessites which contain calcium part their structures. With aim to systematically improve performance such oxide materials, we used flexible synthetic route prepare three series birnessites, where varied concentrations,...
A set of six multinuclear manganese complexes was screened for the ability to catalyse reactions yielding O2 under coherent experimental conditions; we identify a much larger number compounds than previously known that oxygen formation.
Oxygen formation was detected for the oxidations of various multinuclear manganese complexes by oxone (HSO5−) in aqueous solution. To determine to what extent water source evolved O2, H218O isotope-labelling experiments coupled with membrane inlet mass spectrometry (MIMS) were carried out. We discovered that during reaction [Mn2(OAc)2(bpmp)]+ (1), stoichiometrically labelled oxygen (18O2) formed. This is first example a homogeneous mediated synthetic complex where addition strong chemical...
Abstract Oxygen evolution catalysed by calcium manganese and manganese‐only oxides was studied in 18 O‐enriched water. Using membrane‐inlet mass spectrometry, we monitored the formation of different O 2 isotopologues 16 , such reactions simultaneously with good time resolution. From analysis data, conclude that entirely pathways dioxygen catalysis exist for involving hydrogen peroxide (H ), persulfate (HSO 5 − ) or single‐electron oxidants as Ce IV [Ru III (bipy) 3 ] 3+ . Like oxide...
The water-soluble tin(IV) porphyrin dichlorido-5,10,15,20-tetrakis(p-carboxyphenyl)-porphyrinato-tin(IV) (SnTPPC, 1) was synthesised as a mimic of biological chlorophyll photosensitisers. In natural photosynthesis, pigments start the multi-electron transfer processes resulting in water-oxidation and NADP+-reduction. photochemical properties compound 1 were characterised by measuring absorption fluorescence spectra. Electrochemical measurements water revealed well-suited redox potentials for...
A new precursor method using glycinate/nitrate capped Ce<sub>6</sub> clusters enables the synthesis of Ce(<sc>iv</sc>) MOFs with reactive linkers.
A first comparative study on 1D-, 2D- and 3D-manganese oxides supported by iron oxide nanoparticles for use as water oxidation catalysts is presented.
Manganese oxide (MnOx ) electrocatalysts are examined herein by in situ soft X-ray absorption spectroscopy (XAS) and resonant inelastic scattering (RIXS) during the oxidation of water buffered borate (pH 9.2) at potentials from 0.75 to 2.25 V vs. reversible hydrogen electrode. Correlation L-edge XAS data with previous mechanistic studies indicates MnIV is highest state involved catalytic mechanism. MnOx transformed into birnessite 1.45 does not undergo further structural phase changes. At...
Recent results concerning molecular molybdenum sulfido clusters as model systems for heterogeneous hydrogen evolution catalysis by sulfides are summarized and also compared to the related chemistry of active site enzyme Mo-nitrogenase.
Abstract The efficient catalysis of the four-electron oxidation water to molecular oxygen is a central challenge for development devices production solar fuels. This equally true artificial leaf-type structures and electrolyzer systems. Inspired by evolving complex Photosystem II, biological catalyst this reaction, scientists around globe have investigated possibility use manganese oxides (“MnO x ”) task. perspective article will look at selected examples from last about 10 years research in...
A 1-year field study monitoring depth profiles of picoplankton and physicochemical data in the oligotrophic Lake Lucerne (Switzerland) showed that picocyanobacteria play an important role CaCO3 precipitation process. Laboratory experiments with Mychonastes Chlorella, isolated from Synechococcus using ion selective electrodes, scanning electron microscopy X-ray powder diffraction clearly demonstrated potential for fast effective precipitation. The combination a laboratory confirmed previous...
Abstract Receptor‐specific nuclear targeting requires trifunctional metal complexes. We have synthesized [M(L 2 ‐pept)(L 1 ‐acr)(CO) 3 ] (pept=peptide; acr=acridine‐based agent) in which the fac ‐[M(CO) + moiety (1st function, M= 99m Tc, Re) couples an acridine‐based nuclear‐targeting agent (2nd L ‐acr) and specific cell‐receptor‐binding peptide bombesin (3rd ‐pept). The metal‐mediated coupling is based on mixed ligand [2+1] principle. agents been derivatised with isocyanide group for...
Biomimetisch und effizient: Calcium-Mangan(III)-Mischoxide (siehe Strukturausschnitt: Ca grün, Mn rot, O weiß), die in Elementzusammensetzung Struktur dem aktiven Zentrum des Photosystems II ähneln, sind sehr aktive Katalysatoren für Oxidation von Wasser zu molekularem Sauerstoff. Wie PS wird katalytische Aktivität durch den Einbau Ca2+ gegenüber reinen Mangansystem Mn2O3 erheblich erhöht.
Abstract On the path to an energy transition away from fossil fuels sustainable sources, European Union is for moment keeping pace with objectives of Strategic Energy Technology-Plan. For this trend continue after 2020, scientific breakthroughs must be achieved. One main objective produce solar and water in direct processes accomplish efficient storage a chemical form. This grand challenge. important approach achieve goal Artificial Photosynthesis. The Research Alliance has launched Joint...
Abstract A mild screen‐printing method was developed to coat conductive oxide surfaces (here: fluorine‐doped tin oxide) with micrometer‐thick layers of presynthesized calcium manganese (Ca–birnessite) particles. After optimization steps concerning the printing process and layer thickness, electrodes were obtained that could be used as corrosion‐stable water‐oxidizing anodes at pH 7 yield current densities 1 mA cm −2 an overpotential less than 500 mV. Analyses electrode coatings optimal...
In this work, magnetic nanocomposite particles were prepared for water oxidation reactions. The studied catalysts consist of maghemite (γ-Fe2O3), magnetite (Fe3O4), and manganese ferrite (MnFe2O4) nanoparticles as cores coated in situ with birnessite-type oxide shells characterized by X-ray diffraction, transmission electron microscopy, scanning thermal, chemical, surface analyses, measurements. found to be nearly spherical core–shell architectures average diameter 150 nm. Water catalysis...
The reaction products and intermediates of the three CO-releasing manganese(i) coordination compounds [Mn(tpm)(CO)3]+, [Mn(bpza)(CO)3] [Mn(tpa)(CO)3]+ were analysed by combining IR-spectroscopy, electrochemical measurements single-crystal XRD. intermediate formation biscarbonyl rather facile oxidation these species identified as key steps that accompany CO liberation. For use [MnI(CO)3] complexes light-triggered sources, results indicate in this case photo- redox-chemistry seem to be...
Co<sup>2+</sup> and Ni<sup>2+</sup> doped layered birnessite birnessite-manganese ferrite core–shell catalysts displayed enhanced chemical stability performance in electrochemical water oxidation reactions.