H. Dietz

Preparation of silver nanoparticles on ITO surfaces by a double-pulse method

Abstract The influence of pulse parameters of a potentiostatic double-pulse on the size distribution of silver clusters was investigated. The silver clusters were deposited from a cyanide-containing electrolyte onto indium–tin oxide electrodes. Clusters with particle diameters of 100–300 nm can be prepared on a time scale of minutes. A model is presented, which is able to explain the experimental results.

Double-pulse technique as an electrochemical tool for controlling the preparation of metallic nanoparticles

Various structures of silver nanoparticles were generated by means of the double-pulse technique. The interaction of the pulse parameters was modeled to demonstrate that the electrodeposition of nanoparticles can be variably controlled. The results derived showed how to create nanoparticle structures with respect to size, density and monodispersity according to the application goal.

The effect of additives on the positive lead-acid battery electrode

Abstract The effect of the additives carboxymethylcellulose (CMC), carbon black, silica gel, and fibres on the manufacture of positive active material and on the cycle life was investigated by means of porosimetry, inner surface (BET) determination, X-ray diffractometry, chemical analysis, and by measuring the course of the potential, by testing the low rate and high rate capacities and by overcharge cycling tests. It was shown that the additives can be classified, according to their mode of action, into additives (a) increasing the water accumulating capacity of the paste, (b) influencing the crystallization of the mass, (c) increasing the electronic conductivity of the mass, (d) stabilizing the mass. Types (a), (b), and (c) affect the manufacture of active material and the initial capacities, whereas additive (d) improves the cycle life.

Influence of substituted benzaldehydes and their derivatives as inhibitors for hydrogen evolution in lead/acid batteries

Abstract The influence of substituted benzaldehydes and their derivatives as inhibitors for hydrogen evolution on smooth and porous negative electrodes of the lead/acid system is investigated by cyclic voltammetric measurements. The experiments have been carried out with and without the presence of antimony. The effect of the inhibitors can be distinguished by a moderate and a strong inhibiting action. Use of these inhibitors in flooded lead/acid batteries can reduce water loss during cycling by 50%.

On the hydrogen balance in sealed lead/acid batteries and its effect on battery performance

Abstract An overview is provided on the basic principles of decreasing hydrogen pressure in sealed lead/acid batteries. Approaches that are basedon present technology, as well as other possibilities for suppressing hydrogen evolution and oxidizing hydrogen, are studied and discussed. The results emphasize the relevance of so-called hydrogen-evolution inhibitors for industrial applications.

Noble metal-free catalysts for the hydrogen/oxygen recombination in sealed lead/acid batteries using immobilized electrolytes

Abstract In order to remove hydrogen in sealed lead/acid batteries operating on oxygen cycle the facility to recombine hydrogen and oxygen at a catalyst in the gas phase was studied. Based on the assumption of an electrochemical mechanism, several catalytic materials were investigated. It has been shown that noble metal-free composite materials based on tungsten carbide (WC) and carbon can be applied as catalysts for this purpose. The working conditions for their application in model cells were discussed. The efficiency of such catalysts in sealed lead/acid batteries was also demonstrated.

On the characterization of oxygen recombination in sealed lead-acid batteries

For characterizing the oxygen cycle in sealed lead-acid batteries the technological terms “oxygen recombination efficiency” and “oxygen recombination conditions” are introduced and their different meanings explained. Numerical values are calculated or estimated from plots of overpressure against time. Emphasis is placed on investigations of the influence of technological parameters on oxygen recombination conditions.

Untersuchungen zur inhibierung der H2-entwicklung an antimonkontaminierten bleielektroden im schwefelsauren elektrolyten

Zusammenfassung Mittels zyklovoltammetrischer Untersuchungen wurde die inhibierende Wirkung von Zusatzen zum Schwefelsaureelektrolyten auf die Wasserstoffentwicklung an der Bleielektrode insbesondere in Gegenwart von Antimon untersucht. Es wurde gefunden, dass eine Reihe insbesondere organische Zusatze an der Elektrodenoberflache adsorbiert werden und dadurch die Wasserstoffuberspannung auch an der antimonkontaminierten Bleielektrode erhoht werden kann. Andererseits wird durch sie z.T. die Kinetik der Pb/PbO 4 -Reaktion beeinflusst, als auch die Antimonabscheidung in einer die Wasserstoffuberspannung weniger senkenden Modifikation hervorgerufen. Derartige Zusatze wurden in gasdichten Bleiakkumulatorzellen zur Verringerung des Wasserstoffzellinnendrucks untersucht.

Nanocrystalline structures of metal deposits studied by locally resolved Raman microscopy

Confocal laser microscopy coupled with fluorescence- and Raman spectroscopy was used to investigate optical properties of single silver nuclei (clusters). A double pulse method was used to prepare cluster distributions of homogeneous size and surface density. The clusters show large spectral differences and a characteristic time dependence of the Raman bands.

Zum zelldruck geschlossener bleiakkumulatoren

Zusammenfassung Es wird der Zelldruck geschlossener Bleiakkumulatoren in der Uberladesphase und der sich anschliesenden Ruhephase auf Basis der Diffusionsbestimmtheit der Sauerstoffreduktion berechnet Dabei wird berucksichtigt, das das in der Ruhephase sich in einer Selbstentladereaktion bildene PbSO 4 , die effektive Pb-Reaktionsflache abdeckt. Der Grad der Abdeckung hangt vom Verhaltnis zwischen Sauerstoffangebot und der Grose der Reaktionsflache ab. Es wird eine berechnete und experimentell gemessene Kurve verglichen und weitgehende Ubereinstimmung gefunden. Der Einflus der Parameter: effektive Reaktionsflache, Uberladestromstarke, frei 4 -Kristallitgrose auf den Zelldruck werden diskutiert.