Probleme des konvektiven Stofftransports bei der Elektrolyse

Abstract

Die Vorgange des Stofftransports (elektrische Wanderung, Diffusion, Konvektion) fijhren auch bei der Elektrolyse zu Konzentrationsunterschie$en in der Nahe der Elektrodenoberflache und im lnnern der Losung und.bestirnrnen dodurch die Gro8e des Grenzstrornes, der ein MOO f u r die maxirnale Geschwindigkeit ist, mit der ein elektrochemischer Prozei3 bei gegebenen Ruhrbedingungen ausgefuhrt werden kann.Mit Hilfe der Dirnensionsanalyse und der Grenzschichttheorie der Hydrodynarnik lassen sich fur besonders einfache Falle diese Daten berechnen bzw. abschatzen, wie an Beispielen gezeigt wird. Allgemeine Betrachtungen zum elektrolytischen Stofftransport 2,Chemie-1ng.-Techn.

Hydrogen Bubble Templated Metal Foams as Efficient Catalysts of CO2 Electroreduction

“…While for metal depositions in quiescent systems, the thickness of the diffusion layer of metal ions can (over time) extend to even a few hundreds of micrometers, it was shown that for quickly gas evolving electrodes (volumetric gas evolution rate normalized to surface area: 100 cm 3 min −1 , corresponding to hydrogen evolution occurring with a current density of about 5 A cm −2 ), the diffusion layer becomes only a few micrometers thick and the coverage of the surface by gas bubbles can exceed 30 % [54] . Thus, at electrodes that evolve hydrogen at a high rate, due to the decrease of the diffusion layer thickness and the corresponding increase of j lim,dep , the “effective overpotential” (a term coined by Nikolić et al [31] …”

General Theory of Disperse Metal Electrodeposits Formation

“…It is known that the hydrogen evolution effects onto the hydrodynamic conditions inside the electrochemical cell [48][49][50]. The increase in hydrogen evolution rate leads to the decrease of the diffusion layer thickness and hence to the increase of limiting diffusion current density of electrode processes.…”

Gas-Evolving Electrodes

“…(8) Vapor bubbles are formed out of sufficiently superheated liquids at nucleation sites on heated surfaces and grow by thermal conduction from the surrounding liquid (and from a liquid microlayer at the base of the bubble (9)) until the departure size is reached and the bubble breaks off. The consecutive bubble forms at the same nucleation site.…”