Fachgebiet Technische Chemie

34 Items

Recent Submissions
High throughput modules for performance and mechanism assessment of flame retardants in polymeric materials

Rabe, Sebastian (2017)

Due to the ever-increasing number of additives, adjuvants, synergists, and fillers, together with variations in concentration, particle size distribution and other modifications, methods for accelerated assessment of flame retarded polymeric materials are strongly needed. This work presents two novel approaches to assess the rapid screening of flame retardants in polymeric materials. Furthermor...

Record activity and stability of dealloyed bimetallic catalysts for proton exchange membrane fuel cells

Han, Binghong ; Carlton, Christopher E. ; Kongkanand, Anusorn ; Kukreja, Ratandeep S. ; Theobald, Brian R. ; Gan, Lin ; O'Malley, Rachel ; Strasser, Peter ; Wagner, Frederick T. ; Shao-Horn, Yang (2015)

We demonstrate the unprecedented proton exchange membrane fuel cell (PEMFC) performance durability of a family of dealloyed Pt-Ni nanoparticle catalysts for the oxygen reduction reaction (ORR), exceeding scientific and technological state-of-art activity and stability targets. We provide atomic-scale insight into key factors controlling the stability of the cathode catalyst by studying the infl...

Reliable palladium nanoparticle syntheses in aqueous solution: the importance of understanding precursor chemistry and growth mechanism

Kettemann, Frieder ; Wuithschick, Maria ; Caputo, Gianvito ; Krähnert, Ralph ; Pinna, Nicola ; Rademann, Klaus ; Polte, Jörg (2015)

Reliable protocols for the synthesis of palladium nanoparticles (Pd-NPs) in aqueous solution are rarely found and the corresponding growth mechanisms often remain unknown. Furthermore, syntheses of Pd-NPs always demand the use of stabilizing agents which are often unfavorable for catalytic applications. In this contribution, the importance of the palladium precursor chemistry as a prerequisite ...

From molecular copper complexes to composite electrocatalytic materials for selective reduction of CO2 to formic acid

Tran Ngoc Huan ; Andreiadis, Eugen S. ; Heidkamp, Jonathan ; Simon, Philippe ; Derat, Etienne ; Cobo, Saioa ; Royal, Guy ; Bergmann, Arno ; Strasser, Peter ; Dau, Holger ; Artero, Vincent ; Fontecave, Marc (2015)

The development of new energy storage technologies is central to solving the challenges facing the widespread use of renewable energies. An option is the reduction of carbon dioxide (CO2) into carbon-based products which can be achieved within an electrochemical cell. Future developments of such processes depend on the availability of cheap and selective catalysts at the electrode. Here we show...

Oxide-supported Ir nanodendrites with high activity and durability for the oxygen evolution reaction in acid PEM water electrolyzers

Oh, Hyung-Suk ; Nong, Hong Nhan ; Reier, Tobias ; Gliech, Manuel ; Strasser, Peter (2015)

Reducing the noble-metal catalyst content of acid Polymer Electrolyte Membrane (PEM) water electrolyzers without compromising catalytic activity and stability is a goal of fundamental scientific interest and substantial technical importance for cost-effective hydrogen-based energy storage. This study presents nanostructured iridium nanodendrites (Ir-ND) supported on antimony doped tin oxide (AT...

Time-resolved in situ studies on the formation mechanism of iron oxide nanoparticles using combined fast-XANES and SAXS

Kabelitz, Anke ; Guilherme, Ana ; Joester, Maike ; Reinholz, Uwe ; Radtke, Martin ; Bienert, Ralf ; Schulz, Katrin ; Schmack, Roman ; Krähnert, Ralph ; Emmerling, Franziska (2015)

The reaction of iron chlorides with an alkaline reagent is one of the most prominent methods for the synthesis of iron oxide nanoparticles. We studied the particle formation mechanism using triethanolamine as reactant and stabilizing agent. In situ fast-X-ray absorption near edge spectroscopy and small-angle X-ray scattering provide information on the oxidation state and the structural informat...

Hydrophilic non-precious metal nitrogen-doped carbon electrocatalysts for enhanced efficiency in oxygen reduction reaction

Hao, Guang-Ping ; Sahraie, Nastaran Ranjbar ; Zhang, Qiang ; Krause, Simon ; Oschatz, Martin ; Bachmatiuk, Alicja ; Strasser, Peter ; Kaskel, Stefan (2015)

Exploring the role of surface hydrophilicity of non-precious metal N-doped carbon electrocatalysts in electrocatalysis is challenging. Herein we discover an ultra-hydrophilic non-precious carbon electrocatalyst, showing enhanced catalysis efficiency on both gravimetric and areal basis for oxygen reduction reaction due to a high dispersion of active centres.

An efficient bifunctional two-component catalyst for oxygen reduction and oxygen evolution in reversible fuel cells, electrolyzers and rechargeable air electrodes

Dresp, Sören ; Luo, Fang ; Schmack, Roman ; Kühl, Stefanie ; Gliech, Manuel ; Strasser, Peter (2016)

We report on a non-precious, two-phase bifunctional oxygen reduction and evolution (ORR and OER) electrocatalyst with previously unachieved combined roundtrip catalytic reactivity and stability for use in oxygen electrodes of unitized reversible fuel cell/electrolyzers or rechargeable metal-air batteries. The combined OER and ORR overpotential, total, at 10 mA cm(-2) was a record low value of 0...

Uncovering the prominent role of metal ions in octahedral versus tetrahedral sites of cobalt-zinc oxide catalysts for efficient oxidation of water

Menezes, Prashanth W. ; Indra, Arindam ; Bergmann, Arno ; Chernev, Petko ; Walter, Carsten ; Dau, Holger ; Strasser, Peter ; Drieß, Matthias (2016)

The fabrication and design of earth-abundant and high-performance catalysts for the oxygen evolution reaction (OER) are very crucial for the development and commercialization of sustainable energy conversion technologies. Although spinel catalysts have been widely explored for the electrochemical oxygen evolution reaction (OER), the role of two geometrical sites that influence their activities ...

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...