DECHEMA

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.

Electrocatalytic Activity of Platinum modified Polypyrrole Films for the Methanol Oxidation reaction

Abstract: The catalytic activity of platinum modified polypyrrole films prepared in different ways was studied for the methanol oxidation reaction. Surprisingly, no catalytic activity was observed for films modified with colloidal platinum particles incorporated into the film during its synthesis or for the film synthesised with tetrachloroplatinate complex as a nucleophilic counter-ion, which was subsequently cathodically reduced. On the other hand, high catalytic activity was observed for platinum deposited onto pre-synthesised polypyrrole film. The platinum load, film thickness and potential of platinum deposition were found to be important parameters. High electrocatalytic activity was also observed for platinum layers deposited directly onto the glassy carbon (GC) support. However, in the latter case the stability of the electrocatalytic activity was lower when compared with the polypyrrole film modified by cathodically deposited Pt.

The role of alloying elements in commercial alloys for corrosion resistance in oxidizing-chloridizing atmospheres. Part I: Literature evaluation and thermodynamic calculations on phase stabilities

Abstract: In several high temperature processing environments the presence of chlorine may significantly reduce the life-time of the components. Although metallic materials have been widely used under such conditions there is still a need for data on the role of the different alloying elements in commercial alloys. In the present work this role was investigated in detail at temperatures between 650 and 1000°C in synthetic air containing up to 2 vol.% Cl2. Before starting the experimental investigation a detailed literature evaluation on chlorine high temperature corrosion was performed followed by a thermodynamic assessment of the stability and the partial pressures of the phases formed by the reaction between alloy and environment. The results of this “theoretical approach” are presented in the following first part of the publication while the experimental work will be reported in the second part appearing in a later issue of this journal. Already the results of the “theoretical approach” yield a clear picture of which alloying elements play a detrimental role and which elements are beneficial. These results can be used as a tool for a general assessment of metallic alloys with regard to their performance in oxidizing/chloridizing high temperature environments. In the second part of this work the results from this “theoretical approach” will be compared with the behavior of 14 commercial materials, where the content of the major alloying elements was varied in a systematic manner. Die Rolle der Legierungselemente in kommerziellen Werkstoffen fur die Korrosionsbestandigkeit in oxidierend-chlorierend wirkenden Atmospharen. Teil I: Literaturauswertung und thermodynamische Berechnungen zur Stabilitat der Phasen In einer Reihe von Hochtemperatur-Prozesumgebungen fuhrt die Anwesenheit von chlorhaltigen Verbindungen zu einer deutlichen Verkurzung der Lebensdauer der Anlagenbauteile. Obwohl in diesen Anlagen metallische Legierungen bereits in grosem Umfang eingesetzt werden, besteht immer noch ein ausgepragter Bedarf an Daten zur Rolle des Verhaltens der verschiedenen Legierungselemente unter diesen Bedingungen. In der vorliegenden Arbeit wurde diese Rolle im Detail bei Temperaturen von 650 bis 1000°C in Luft mit Chlorgehalten bis zu 2% vol. untersucht. Vor der Durchfuhrung des experimentellen Teils der Untersuchungen wurde eine umfangreiche Literaturauswertung vorgenommen, gefolgt von thermodynamischen Rechnungen zur Stabilitat und zum Partialdruck der Phasen, die durch die Reaktion der Legierungen mit der Prozesumgebung gebildet werden konnen. Die Ergebnisse dieses “theoretischen Ansatzes” werden im ersten Teil einer zweiteiligen Veroffentlichung vorgestellt, wahrend uber die Ergebnisse der experimentellen Untersuchungen im zweiten Teil berichtet wird, der in einer spateren Ausgabe dieser Zeitschrift erscheint. Bereits die Ergebnisse des “theoretischen Ansatzes” erlauben eine klare Einschatzung, welche Legierungselemente eine positive und welche eine negative Rolle bezuglich der Korrosionsbestandigkeit von metallischen Legierungen in diesen Umgebungen spielen. Diese Ergebnisse konnen als Werkzeug fur die Bewertung des Verhaltens kommerzieller Werkstoffe in oxidierend/chlorierend wirkenden Atmospharen eingesetzt werden. Im zweiten Teil dieser Arbeit werden die Ergebnisse des “theoretischen Ansatzes” mit dem Korrosionsverhalten von 14 kommerziellen Werkstoffen verglichen, bei denen der Gehalt der wichtigsten Legierungselemente in systematischer Weise variiert wurde.

Immobilized redox mediators for electrochemical NAD(P)+ regeneration

Abstract: The applicability of dissolved redox mediators for NAD(P)+ regeneration has been demonstrated several times. Nevertheless, the use of mediators in solutions for sensor applications is not a very convenient strategy since the analysis is not reagentless and long stabilization times occur. The most important drawbacks of dissolved mediators in biocatalytic applications are interferences during product purification, limited reusability of the mediators, and their cost-intensive elimination from wastewater. Therefore, the use of immobilized mediators has both economic and ecological advantages. This work critically reviews the current stateof-art of immobilized redox mediators for electrochemical NAD(P)+ regeneration. Various surface modification techniques, such as adsorption polymerization and covalent linkage, as well as the corresponding NAD(P)+ regeneration rates and the operational stability of the immobilized mediator films, will be discussed. By comparison with other existing regeneration systems, the technical potential and future perspectives of biocatalytic redox reactions based on electrochemically fed immobilized mediators will be assessed.