Volker Brüser

Electrocatalysts for Oxygen Reduction Prepared by Plasma Treatment of Carbon-Supported Cobalt Tetramethoxyphenylporphyrin

during the pyrolysis of CoTMPP. Additionally, solid decomposition products of the oxalate metal and oxides form a framework embedded within the pyrolysis product which is removed by a subsequent acid treatment. Finally, a highly porous carbon matrix with embedded centers is obtained. With this procedure materials with high electrochemical activities toward the oxygen reduction have been achieved in rotating disk electrode RDE measurements in 0.5 M H2SO4 at 0.7 V normal hydrogen electrode NHE close to that of commercial 20% Pt/C E-TEK. However, even with this advanced technique scanning electron microscopy SEM images reveal particles of several micrometer dimension composed of that highly porous material. In technical applications e.g., gas diffusion electrodes in fuel cells this presumably leads to a lower efficiency due to long diffusion pathways for protons and gas molecules. Therefore, alternative synthesis techniques are desired which result in smaller particle sizes 50‐100 nm as it is state of the art for carbon supports which are utilized for commercial platinum catalysts Vulcan, Black Pearls ca. 20 nm. In the last decades plasma treatment of organic material was intensively investigated and is considered as a promising nanotechnological approach. Our contribution shows that the transfer of CoTMPP into highly electrochemical active CoN4 centers embedded in a carbon matrix can be reached by plasma treatment instead of conservative heat-treatment. In order to find optimal operating parameters CoTMPP on Black Pearls was processed by plasma treatment as well as by classical heat-treatment. The obtained products were compared in terms of structure and catalytic activity.

Photocatalytic Hydrogen Production with Copper Photosensitizer–Titanium Dioxide Composites

A series of heteroleptic copper photosensitizers [(

Plasma Synthesis of Polymer‐Capped Dye‐Sensitised Anatase Nanopowders for Visible‐Light‐Driven Hydrogen Evolution

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Plasma-Modified Polypropylene as Carrier for the Immobilization of Candida antarctica Lipase B and Pyrobaculum calidifontis Esterase

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Using a Dual Plasma Process to Produce Cobalt-Polypyrrole Catalysts for the Oxygen Reduction Reaction in Fuel Cells II. Analysing the Chemical Structure of the Films

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Using a Dual Plasma Process to Produce Cobalt-Polypyrrole Catalysts for the Oxygen Reduction Reaction in Fuel Cells I. Characterization of the Catalytic Activity and Surface Structure

(SO3Na)2)]+ containing sulfonate anchor groups is described. In the presence of titanium dioxide they form composites, which are active photosensitizers in the light driven reduction of protons. Further stabilization of these systems is achieved by encapsulation within a plasma‐polymerized allylamine (PPAAm) layer. The resulting PPAAm‐CuPS‐TiO2‐composites exhibit a strong absorption in the visible region of the light. Photocatalytic hydrogen production is performed by using only non‐noble metals. In the presence of an iron reduction catalyst a maximum turnover number of 2452 is obtained.

Comparative study of plasma-treated non-precious catalysts for oxygen and hydrogen peroxide reduction reactions

Visible-light-driven photocatalysis is currently attracting a great deal of attention because of its potential application in solar water splitting. However, the development of efficient and durable catalyst systems is still a challenging problem. In Ru dye-sensitised TiO(2) nanopowders, catalyst performances are found to decline as a result of poor bonding of the dye molecule to the TiO(2) surface and subsequent detachment and self-aggregation of the dye. Our strategy to improve the stability of the dye-TiO(2) interface is the encapsulation of the dye/TiO(2) assembly in an amino-group-containing polyallylamine layer anchored to TiO(2). A low-pressure pulsed microwave discharge plasma polymerization process was employed to coat a commercial anatase nanopowder with a thin polyallylamine layer to nanoconfine the adsorbed dye molecules. Electron microscopy and UV/Vis spectroscopy was carried out to characterise the resulting encapsulated nanostructures. The long-term stability of the new nanomaterial as the photoactive component of a water reduction catalyst system for H(2) evolution investigated in a slurry reactor under visible-light irradiation showed stable evolution rates over a period of several days.

Iron–Polypyrrole Catalysts for the Oxygen Reduction in Proton Exchange Membrane Fuel Cells Produced with a Dual Plasma Process Using Varying Magnetron Powers and Process Gases

In this work, the immobilization of two hydrolases on plasma‐modified polypropylene carriers was investigated. Treating Accurel MP1001 with an oxygen plasma was found most suitable to increase the hydrophilicity and to allow for efficient immobilization. Thus, for lipase B from Candida antarctica and for an esterase from Pyrobaculum calidifontis esterase (PestE) a 5‐fold and 14‐fold increase, respectively, in immobilization yield resulted compared to untreated carrier. In contrast to the oxygen‐modified support, modification of the polypropylene carrier with ammonia plasma showed no positive effect. Furthermore, it could be shown that immobilized PestE catalyzed enantioselective transesterification of α‐phenylethanol in vinyl acetate, whereas the free enzyme showed no activity. Both hydrolases could be recycled five times without significant loss of activity.

Morphology, Optical Properties and Photocatalytic Activity of Photo- and Plasma-Deposited Au and Au/Ag Core/Shell Nanoparticles on Titania Layers

The chemical structure of cobalt--polypyrrole -- produced by a dual plasma process -- is analysed by means of X-ray photoelectron spectroscopy (XPS), near edge X-ray absorption spectroscopy (NEXAFS), X-ray diffraction (XRD), energy-dispersive X-Ray spectroscopy (EDX) and extended x-ray absorption spectroscopy (EXAFS).It is shown that only nanoparticles of a size of 3\,nm with the low temperature crystal structure of cobalt are present within the compound. Besides that, cobalt--nitrogen and carbon--oxygen structures are observed. Furthermore, more and more cobalt--nitrogen structures are produced when increasing the magnetron power. Linking the information on the chemical structure to the results about the catalytic activity of the films -- which are presented in part I of this contribution -- it is concluded that the cobalt--nitrogen structures are the probable catalytically active sites. The cobalt--nitrogen bond length is calculated as 2.09\,\AA\ and the carbon--nitrogen bond length as 1.38\,\AA.

Study of high-current arcs and its interaction with side walls and layers

A new dual plasma coating process to produce platinum-free catalysts for the oxygen reduction reaction in a fuel cell is introduced. The catalysts thus produced were analysed with various methods. Electrochemical characterisation was carried out by cyclic voltammetry, rotating ring- and rotating ring-disk electrode. The surface porosity of the different catalysts thus obtained was characterised with the nitrogen gas adsorption technique and scanning electron microscopy was used to determine the growth mechanisms of the films. It is shown that catalytically active compounds can be produced with this dual plasma process. Furthermore, the catalytic activity can be varied significantly by changing the plasma process parameters. The amount of H