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Institution

DECHEMA

NonprofitFrankfurt am Main, Germany
About: DECHEMA is a nonprofit organization based out in Frankfurt am Main, Germany. It is known for research contribution in the topics: Corrosion & Oxide. The organization has 756 authors who have published 1307 publications receiving 25693 citations.
Topics: Corrosion, Oxide, Coating, Alloy, Catalysis


Papers
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Journal ArticleDOI
TL;DR: A mediated electroenzymatic process to regenerate the NADPH in combination with an old yellow enzyme was investigated and process conditions with high productivities and 90% electron transfer efficiency were identified.
Abstract: Old yellow enzymes are able to catalyze asymmetric C=C reductions. A mediated electroenzymatic process to regenerate the NADPH in combination with an old yellow enzyme was investigated. Due to the fact that the overall process was affected by a broad set of parameters, a design of experiments (DoE) approach was chosen to identify suitable process conditions. Process conditions with high productivities of up to 2.27 mM/h in combination with approximately 90% electron transfer efficiency were identified.

13 citations

Journal ArticleDOI
K. Jüttner1, D. Becker1
TL;DR: In this article, the potential and rotation dependence of the impedance spectra can be described quantitatively in terms of a model based on diffusion controlled charge transfer on partially blocked electrode surfaces and direct evidence for the nonhomogeneous current distribution on the diamond surface was obtained by SECM measurements.
Abstract: Charge transfer on boron doped diamond (BDD) electrodes was studied by cyclic voltammetry and electrochemical impedance spectroscopy. The diamond films of 5 μm thickness and boron content between 200 ppm and 3000 ppm were prepared by the hot filament CVD technique on niobium substrate and mounted in a Teflon holder as rotating disk electrodes. The electrochemical measurements were carried out in aqueous electrolyte solutions of 0.5 M Na2SO4 + 5 mM K3[Fe(CN)6]/K4[Fe(CN)6]. Significant deviation in the redox behaviour of BDD and active Pt electrodes was indicated by a shift of the peak potentials in the cyclic voltammograms with increasing sweep rate and lower limiting diffusion current densities under rotating disk conditions. In the impedance spectra an additional capacitive element appeared at high frequencies. The potential and rotation dependence of the impedance spectra can be described quantitatively in terms of a model based on diffusion controlled charge transfer on partially blocked electrode surfaces. Direct evidence for the non-homogeneous current distribution on the diamond surface was obtained by SECM measurements.

13 citations

Journal ArticleDOI
TL;DR: The application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2‐butanol in a bubble column reactor is demonstrated, demonstrating the applicability ofperoxygenases for preparative hydroxymation of such inert, Gaseous substrates at mild reaction conditions.
Abstract: Unspecific peroxygenases have recently gained significant interest due to their ability to catalyse the hydroxylation of non-activated C−H bonds using only hydrogen peroxide as a co-substrate. However, the development of preparative processes has so far mostly concentrated on benzylic hydroxylations using liquid substrates. Herein, we demonstrate the application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2-butanol in a bubble column reactor. The influence of hydrogen peroxide feed rate and enzyme loading on product formation, overoxidation to butanone and catalytic efficiency is investigated at 200 mL scale. The process is scaled up to 2 L and coupled with continuous extraction. This setup allowed the production of 115 mmol 2-butanol and 70 mmol butanone with an overall total turnover number (TTN) of over 15.000, thereby demonstrating the applicability of peroxygenases for preparative hydroxylation of such inert, gaseous substrates at mild reaction conditions.

12 citations

Journal ArticleDOI
TL;DR: In this paper, a new type of purely inorganic coatings for corrosion and abrasion protection was proposed based on chemical nanotechnology glass-like protective coatings thermally processed at comparatively lower temperatures around 500°C.
Abstract: Nanoparticles and nanostructured films have gained an increasing interest for industrial application in the last years. Based on chemical nanotechnology glass-like protective coatings thermally processed at comparatively lower temperatures around 500°C were developed for metal substrates by two different ways. Starting from polymeric sols (suspension consisting of branched macromolecules) containing multicomponent oxide of the SiO2-B2O3-P2O5-Na2O system produced by hydrolysis and polycondensation of an alkoxide mixture under acidic condition, thin, hard, transparent, crack-free and corrosion resistant coatings could be applied to aluminium and steel. Coatings from particulate sols (suspension consisting of solid particles) containing multicomponent oxide synthesized under basic condition by electrophoretic deposition (EPD) proved to be a promising method when very thick coatings are required. Both routes offer the potential of a new type of purely inorganic coatings for corrosion and abrasion protection. Nano-Email: ein neuer Weg zur Erzeugung glasartiger Schutzschichten fur Metalle In jungerer Zeit haben nanotechnologisch basierte Herstellungsverfahren fur Oberflachenschutzschichten zunehmend an Bedeutung gewonnen. In der vorliegenden Arbeit wurden solche Schichten auf zwei Wegen erzeugt, wobei in beiden Fallen eine thermische Nachbehandlung bei vergleichsweise niedrigen Temperaturen um 500°C zur thermischen Verdichtung und Uberfuhrung in eine rein anorganische Schicht durchgefuhrt wurde. Im ersten Fall wurde mit Polymer-Solen gestartet, die durch Hydrolyse und Polykondensation von Alkoxiden unter saurer Katalyse hergestellte Multikomponentenoxide des Systems SiO2-B2O3-P2O5-Na2O enthalten. Auf diese Weise konnten dunne, harte, transparente, risfreie und korrosionsbestandige Schichten auf Aluminium und Stahl aufgebracht werden. Im zweiten Fall wurden Sole mit festen Multikomponenten-Nanopartikeln verwendet, die sol-gel-technisch unter basischer Katalyse synthetisiert wurden. Schichten wurden mit Hilfe der elektrophoretischen Abscheidung auf Metallsubstrate aufgebracht. Diese Methode war besonders fur die Aufbringung dicker Schichten geeignet. Beide Methoden besitzen das Potential fur die Entwicklung neuartiger Schutzschichten gegen Korrosion und Abrasion.

12 citations

Journal ArticleDOI
TL;DR: In this article, single-walled carbon nanotubes (SWCNTSs) were used as Pt and PtRu catalyst support in the direct methanol fuel cell (DMFC) anode.
Abstract: Carbon Vulcan XC72 is still considered as the standard catalyst support in gas diffusion electrodes for low temperature polymer fuel cell applications. Because of its relatively low specific area and poor corrosion resistance, alternative materials such as carbon nanotubes (CNTs) are currently the focus of numerous investigations. This work reports on the test of single-walled carbon nanotubes (SWCNTSs) as Pt and PtRu catalyst support in the direct methanol fuel cell (DMFC) anode. After the treatment of the CNTs in air at 300°C or in a high concentrated nitric acid solution, power densities of 152 and 157 mW cm -2 have been reached under DMFC conditions at 2 bar abs , and 80°C. The anodic and cathodic Pt loadings amounted to 1 mg cm -2 . The performance of the membrane electrode assembly (MEA) with a PtRu-SWCNT anode was about 10-15% higher than that of the MEA with a conventional as-prepared PtRu-Vulcan XC72 system. This was principally ascribed to higher catalyst utilization, lower impedance, and methanol crossover of the carbon-nanotube-based electrodes compared to those of the carbon-Vulcan-based one.

12 citations


Authors

Showing all 760 results

NameH-indexPapersCitations
Wolf B. Frommer10534530918
Michael W. Anderson10180863603
João Rocha93152149472
Martin Muhler7760625850
Michael Hunger6029511370
Ivars Neretnieks442247159
Michael Schütze403436311
Jens Schrader381294239
Roland Dittmeyer312063762
Lei Li291984003
Dirk Holtmann291073033
Lasse Greiner26741994
Klaus-Michael Mangold23571590
A. Rahmel23591967
Gerhard Kreysa22781305
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Performance
Metrics
No. of papers from the Institution in previous years
YearPapers
20231
20227
202145
202053
201949
201844