Fachgebiet Technische Chemie

25 Items

Recent Submissions
Theoretische Untersuchung der spektroskopischen Eigenschaften biologischer und synthetischer molekularer Spincluster

Ghassemi Tabrizi, Shadan (2017)

Molekulare Spincluster aus zwei bis acht austauschgekoppelten Übergangsmetallzentren erfüllen in Metalloproteinen vielfältige Funktionen, vor allem beim Elektronentransfer und in der biochemischen Katalyse; Eisen-Schwefel-Cluster finden sich in allen bekannten Lebensformen. Von einem grundlegenden Verständnis der intrinsisch quantenmechanischen Eigenschaften solcher Systeme verspricht man sich ...

Future challenges in heterogeneous catalysis: understanding catalysts under dynamic reaction conditions

Kalz, Kai F. ; Krähnert, Ralph ; Dvoyashkin, Muslim ; Dittmeyer, Roland ; Gläser, Roger ; Krewer, Ulrike ; Reuter, Karsten ; Grunwaldt, Jan-Dierk (2017)

In the future, (electro-) chemical catalysts will have to be more tolerant towards a varying supply of energy and raw materials. This is mainly due to the fluctuating nature of renewable ener-gies. For example, power-to-chemical processes require a shift from steady-state operation towards operation under dynamic reaction conditions. This brings along a number of demands for the design of both ...

Structure-activity investigations of mixed Ni-Fe oxides as catalysts for electrochemical water splitting

Görlin, Eva Mikaela Charlotte (2017)

A balanced utilization of energy requires new approaches in catalysis, to reach sufficient levels of production of renewable energy. Specifically, there is a need of efficient catalysts for energy utilization, conversion, and storage. Research concerning electrochemical water splitting has attracted attention due to the possibility to utilize water in integrated solar-to-water splitting device...

Property-performance relationships of catalysts in the oxidative coupling of methane

Schmack, Roman (2017)

The catalytic oxidative coupling of methane (OCM) is a „dream reaction“ of heterogeneous catalysis, as it provides a direct conversion route of methane to the value-added and easily transportable C2 coupling products ethane and ethene. Since its first description in the early 1980s, a multitude of catalysts containing nearly any element have been tested, but so far the development of an economi...

Sustainable biomass potential for biofuels

Lossau, Selma (2017)

There is a large interest in biofuels in Brazil and India as a substitute to fossil fuels, with a purpose of enhancing energy security and promoting rural development. The critical question is whether there is adequate spare land available in Brazil and India that is suited for biofuel feedstock production. For these reasons, Daimler AG launched a project in co-operation with the Internationa...

In situ observation of reactive oxygen species forming on oxygen-evolving iridium surfaces

Pfeifer, Verena ; Jones, Travis E. ; Velasco Vélez, Juan J. ; Arrigo, Rosa ; Piccinin, Simone ; Hävecker, Michael ; Knop-Gericke, Axel ; Schlögl, Robert (2017)

Water splitting performed in acidic media relies on the exceptional performance of iridium-based materials to catalyze the oxygen evolution reaction (OER). In the present work, we use in situ X-ray photoemission and absorption spectroscopy to resolve the long-standing debate about surface species present in iridium-based catalysts during the OER. We find that the surface of an initially metalli...

Reactive oxygen species in iridium-based OER catalysts

Pfeifer, Verena ; Jones, Travis E. ; Wrabetz, Sabine ; Massué, Cyriac ; Velasco Vélez, Juan J. ; Arrigo, Rosa ; Scherzer, Michael ; Piccinin, Simone ; Hävecker, Michael ; Knop-Gericke, Axel ; Schlögl, Robert (2016)

Tremendous effort has been devoted towards elucidating the fundamental reasons for the higher activity of hydrated amorphous IrIII/IV oxyhydroxides (IrOx) in the oxygen evolution reaction (OER) in comparison with their crystalline counterpart, rutile-type IrO2, by focusing on the metal oxidation state. Here we demonstrate that, through an analogy to photosystem II, the nature of this reactive s...

Identification of reactive oxygen species in iridium-based OER catalysts by in situ photoemission and absorption spectroscopy

Pfeifer, Verena (2017)

A change in our energy supply from fossil fuels to intermittent renewables requires energy storage capacity. Part of this capacity may be delivered from chemical energy conversion relying on H2 as basic fuel. Renewable H2 can be generated using proton exchange membrane (PEM) electrolyzers able to adapt to the varying voltage inputs of intermittent sources. Such PEM electrolyzers operate in acid...

CO2 utilisation today : report 2017

Zimmermann, Arno ; Kant, Marvin ; Strunge, Till ; Tzimas, Evangelos ; Leitner, Walter ; Arlt, Wolfgang ; Styring, Peter ; Arning, Katrin ; Ziefle, Martina ; Meys, Raoul ; Kätelhön, Arne ; Bardow, André ; Castillo Castillo, Arturo ; Flanders, Nicholas ; Marinić, Saša ; Mechnig, Stefan-Paul (2017)

This report provides perspectives on CO2 utilisation from a variety of angles: interviews with scientists, essays on business, environment and social impact, as well as stories from CO2-utilising companies. While the authors’ views differ on whether and how CO2 utilisation could be done, all agree that large-scale CO2 utilisation would have a significant impact: It could not only change the way...

Innovationsprojekte schneller zum Erfolg führen

Streit, Bettina Marianne von (2016)

Das Ziel der vorliegenden Arbeit ist die Entwicklung einer Entscheidungshilfe zur optimalen Methodenauswahl, um Entwicklungsprozesse in der chemischen Industrie zu beschleunigen. Die Forschungslücke besteht in der Verzahnung von praxisbezogenen Methoden und Technologien, die innerhalb der Fachdisziplinen der chemischen Forschung und Entwicklung (F&E) entstehen, mit dem aktuellen Forschungsstand...

Water oxidation catalysts

Zachäus, Carolin (2016)

Climate change has been widely recognized as a major environmental problem facing the world today. According to IPCC, this is related to the increase in greenhouse gas concentrations, mainly as a result of the combustion of fossil-fuels. To reconcile this, a transition from fossil-fuels to renewable-based energy sources is unavoidable. Solar water splitting has attracted significant attention t...

Mesoporous oxides as efficient catalysts for the electrocatalytic oxygen evolution reaction (OER)

Bernicke, Michael (2016)

Hydrogen is considered an important energy carrier and feedstock for industrial applications. The generation of hydrogen can be realised by electrocatalytic water splitting. However, the efficiency of water electrolysers is limited by the slow kinetics of oxygen evolution reaction (OER). An increase in mass based OER activity is mandatory for a lower capital cost of electrolyser cells. In this...

Asymmetric reduction of ketones with recombinant E. coli whole cells in neat substrates

Jakoblinnert, Andre ; Mladenov, Radoslav ; Paul, Albert ; Sibilla, Fabrizio ; Schwaneberg, Ulrich ; Ansorge-Schumacher, Marion B. ; de María, Pablo Domínguez (2011)

The asymmetric reduction of ketones is performed by using lyophilized whole cells in neat substrates with defined water activity (aw). Ketones and alcohols prone to be unstable in aqueous media can now be converted via biocatalysis.

Iron-based pre-catalyst supported on polyformamidine for C-C bond formation

Enthaler, Stephan ; Krackl, Sebastian ; Epping, Jan Dirk ; Eckhardt, Björn ; Weidner, Steffen M. ; Fischer, Anna (2012)

In the present study the incorporation of iron into an organic polymer, composed of formamidine subunits [R–N[double bond, length as m-dash]C(H)–NH–R], has been examined. The catalytic ability of the recyclable material was investigated in the iron-catalyzed formation of C–C bonds. After optimization of the reaction conditions, excellent yields and chemoselectivities were feasible.

Nitrogen-doped coatings on carbon nanotubes and their stabilizing effect on Pt nanoparticles

Tuaev, Xenia ; Paraknowitsch, Jens Peter ; Illgen, René ; Thomas, Arne ; Strasser, Peter (2012)

A homogeneous coating of nitrogen-doped carbon on carbon nanotubes is performed using ionic liquids. The N-doped material is employed as a support for nanoparticles. Electrochemical degradation behavior is monitored in situ and compared to an unmodified material. The strongly enhanced stability is explained on the basis of a Pt–nitrogen interaction.

Bifunctional anode catalysts for direct methanol fuel cells

Rossmeisl, Jan ; Ferrin, Peter ; Tritsaris, Georgios A. ; Nilekar, Anand Udaykumar ; Koh, Shirlaine ; Bae, Sang Eun ; Brankovic, Stanko R. ; Strasser, Peter ; Mavrikakis, Manos (2012)

Using the binding energy of OH* and CO* on close-packed surfaces as reactivity descriptors, we screen bulk and surface alloy catalysts for methanol electro-oxidation activity. Using these two descriptors, we illustrate that a good methanol electro-oxidation catalyst must have three key properties: (1) the ability to activate methanol, (2) the ability to activate water, and (3) the ability to re...

The preparation, characterisation and electronic structures of 2,4-pentadiynylnitrile (cyanobutadiynyl) complexes

Bock, Sören ; Eaves, Samantha G. ; Parthey, Matthias ; Kaupp, Martin ; Le Guennic, Boris ; Halet, Jean-François ; Yufit, Dmitry S. ; Howard, Judith A. K. ; Low, Paul J. (2013)

Convenient preparative routes to mononuclear ruthenium complexes containing the 2,4-pentadiynylnitrile, or cyanobutadiynyl, ligand are described. The electronic properties of the [C5N]− ligand are closely related to those of not only the cyanide ([CN]−) and 2-propynylnitrile or cyanoacetylide ([C[triple bond, length as m-dash]CC[triple bond, length as m-dash]N]−) ligands, but also those of the ...

Phosphorus-doped porous carbons as efficient electrocatalysts for oxygen reduction

Wu, Jiao ; Yang, Zhenrong ; Li, Xiaowei ; Sun, Qijun ; Jin, Chao ; Strasser, Peter ; Yang, Ruizhi (2013)

Efficient electrocatalysts for the oxygen reduction reaction (ORR) play a critical role in the performance of fuel cells and metal–air batteries. In this study, we report a facile synthesis of phosphorus (P)-doped porous carbon as a highly active electrocatalyst for the ORR. Phosphorus-doped porous carbon was prepared by simultaneous doping and activation of carbon with phosphoric acid (H3PO4) ...

Electrochemical water splitting by layered and 3D cross-linked manganese oxides: correlating structural motifs and catalytic activity

Bergmann, Arno ; Zaharieva, Ivelina ; Dau, Holger ; Strasser, Peter (2013)

Manganese based precious metal-free electrocatalysts for the oxygen evolution reaction (OER) are promising materials for energy storage systems based on dark or photo-coupled water electrolysis, because they are active, inexpensive and of low toxicity. In this work, atomic scale structure–activity relationships of two different nano-structured manganese oxides, MnOx, are established using a com...

On the faradaic selectivity and the role of surface inhomogeneity during the chlorine evolution reaction on ternary Ti-Ru-Ir mixed metal oxide electrocatalysts

Zeradjanin, Aleksandar R. ; Menzel, Nadine ; Schuhmann, Wolfgang ; Strasser, Peter (2014)

The faradaic selectivity of the chlorine evolution reaction (CER) and oxygen evolution reaction (OER) on the industrially important Ti–Ru–Ir mixed metal oxide is discussed. Absolute evolution rates as well as volume fractions of Cl2 and O2 were quantified using differential electrochemical mass spectrometry (DEMS), while the catalyst surface redox behavior was analyzed using cyclic voltammetry....