Rotating disk electrode

A rotating disk electrode (RDE, engl. Rotating disc electrode ) is an electrochemical test setup, in which the working electrode undergoes rotation by a constant mass transport. This makes it possible to study the mass transport of chemical species to the electrode surface in electrochemical reactions. The rotating disk electrode is an important experimental setup for studying electrochemical catalysts .

construction

Noble metals or glassy carbon in planar design are usually used as the working electrode . The working electrode is mounted on a rotating shaft and lowered into the electrolyte . It rotates up to 3000 / min. As a result of the rotation, a first approximation of a laminar flow is generated along the electrode surface. This makes it possible to study mass transport effects in electrochemical reactions and to determine diffusion coefficients of reacting molecules.

Theoretical description

Levich provided a comprehensive empirical model to describe convection. The following applies to the axial flow along the electrode surface ( ): ${\ displaystyle v_ {x}}$ ${\ displaystyle x = 0}$

{\ displaystyle v_ {x} = - 0.510 \ cdot w ^ {\ frac {3} {2}} v ^ {- {\ frac {1} {2}}} x ^ {2} + 0.333w ^ {2 } v ^ {- 1} x ^ {3}}

Here is the speed of rotation and the viscosity of the electrolyte. For reactants that diffuse slowly, the following equation applies to the resulting current:

{\ displaystyle w}

{\ displaystyle v}

{\ displaystyle I _ {\ mathrm {lim, c}} = 0.62nF \ pi r ^ {2} D ^ {\ frac {3} {2}} v ^ {- {\ frac {1} {6}} } w ^ {\ frac {1} {2}} c}

Here is the number of electrons transferred during the reaction, the Faraday constant , the radius of the working electrode, the diffusion coefficient and the concentration of the reacting species. ${\ displaystyle n}$ ${\ displaystyle F}$ ${\ displaystyle r}$ ${\ displaystyle D}$ ${\ displaystyle c}$

Individual evidence

↑ Cynthia G. Zoski (Ed.): Handbook of Electrochemistry . 1st edition. Elsevier, Amsterdam 2007, ISBN 978-0-444-51958-0 , pp. 840 ff . ( limited preview in Google Book search).
↑ Stephen Treimer, Andrew Tang, Dennis C. Johnson: A Consideration of the Application of Koutecký-Levich Plots in the Diagnoses of Charge-Transfer Mechanisms at Rotated Disk Electrodes . In: Electroanalysis . tape 14 , no. 3 , 2002, ISSN 1521-4109 , p. 165-171 , doi : 10.1002 / 1521-4109 (200202) 14: 33.0.CO; 2-6 .

[1] Cynthia G. Zoski (Ed.): Handbook of Electrochemistry . 1st edition. Elsevier, Amsterdam 2007, ISBN 978-0-444-51958-0 , pp. 840 ff . ( limited preview in Google Book search).

[2] Stephen Treimer, Andrew Tang, Dennis C. Johnson: A Consideration of the Application of Koutecký-Levich Plots in the Diagnoses of Charge-Transfer Mechanisms at Rotated Disk Electrodes . In: Electroanalysis . tape 14 , no. 3 , 2002, ISSN 1521-4109 , p. 165-171 , doi : 10.1002 / 1521-4109 (200202) 14: 33.0.CO; 2-6 .