Hydrodynamic voltammetry is a form of

voltammetry Voltammetry is a category of electroanalytical methods used in analytical chemistry and various industrial processes. In voltammetry, information about an analyte is obtained by measuring the current as the potential is varied. The analytical data ...

in which the

analyte An analyte, component (in clinical chemistry), or chemical species is a substance or chemical constituent that is of interest in an analytical procedure. The purest substances are referred to as analytes, such as 24 karat gold, NaCl, water, etc. ...

solution flows relative to a

working electrode The working electrode is the electrode in an electrochemical system on which the reaction of interest is occurring. The working electrode is often used in conjunction with an auxiliary electrode, and a reference electrode in a three electrode sys ...

. In many

techniques, the solution is intentionally left still to allow

diffusion Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...

controlled

mass transfer Mass transfer is the net movement of mass from one location (usually meaning stream, phase, fraction or component) to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, ...

. When a solution is made to flow, through stirring or some other physical mechanism, it is very important to the technique to achieve a very controlled flux or mass transfer in order to obtain predictable results. These methods are types of

electrochemical Electrochemistry is the branch of physical chemistry concerned with the relationship between electrical potential difference, as a measurable and quantitative phenomenon, and identifiable chemical change, with the potential difference as an outco ...

studies which use

potentiostat A potentiostat is the electronic hardware required to control a three electrode cell and run most electroanalytical experiments. A ''Bipotentiostat'' and ''polypotentiostat'' are potentiostats capable of controlling two working electrodes and ...

s to investigate

reaction mechanisms Reaction may refer to a process or to a response to an action, event, or exposure: Physics and chemistry *Chemical reaction *Nuclear reaction *Reaction (physics), as defined by Newton's third law *Chain reaction (disambiguation). Biology and me ...

related to

redox Redox (reduction–oxidation, , ) is a type of chemical reaction in which the oxidation states of substrate (chemistry), substrate change. Oxidation is the loss of Electron, electrons or an increase in the oxidation state, while reduction ...

chemistry among other

chemical A chemical substance is a form of matter having constant chemical composition and characteristic properties. Some references add that chemical substance cannot be separated into its constituent elements by physical separation methods, i.e., wi ...

phenomenon.Douglas A. Skoog, F. James Holler, Timothy A. Nieman Principles of Instrumental Analysis. Harcourt Brace College Publishers, 1998 .

Structure

Most experiments involve a three electrode setup but the setup configuration varies widely. All cell configurations create a

laminar flow In fluid dynamics, laminar flow is characterized by fluid particles following smooth paths in layers, with each layer moving smoothly past the adjacent layers with little or no mixing. At low velocities, the fluid tends to flow without lateral mi ...

of solution across the

(s) producing a steady-state current determined by solution flow rather than

. The resulting current can be mathematically predicted and modeled. Among the most common hydrodynamic setup involves the working electrodes rotating to create a laminar flow of solution across the electrode surface. Both

rotating disk electrode A rotating disk electrode (RDE) is a working electrode used in three electrode systems for hydrodynamic voltammetry.Bard, A.J.; Faulkner, L.R. Electrochemical Methods: Fundamentals and Applications. New York: John Wiley & Sons, 2nd Edition, 2000. ...

s (RDE) and

rotating ring-disk electrode A rotating ring-disk electrode (RRDE) is a double working electrode used in hydrodynamic voltammetry, very similar to a rotating disk electrode (RDE). The electrode rotates during experiments inducing a flux of analyte to the electrode. This syste ...

s (RRDE) are examples where the working electrode rotates. Other configurations, such as flow cells, use pumps to direct solution at or across the working electrode(s).

Distinction

Hydrodynamic techniques are distinct from still and unstirred experiments such as

cyclic voltammetry Cyclic voltammetry (CV) is a type of potentiodynamic electrochemical measurement. In a cyclic voltammetry experiment, the working electrode potential is ramped linearly versus time. Unlike in linear sweep voltammetry, after the set potential is re ...

where the steady-state current is limited by the diffusion of substrate. Experiments are not however limited to

linear sweep voltammetry Linear sweep voltammetry is a voltammetric method where the current at a working electrode is measured while the potential between the working electrode and a reference electrode is swept linearly in time. Oxidation or reduction of species is regi ...

. The configuration of many cells takes the substrate from one working electrode across another, RRDE for example. The potential of one electrode can be varied as the other is held constant or varied. The flow rate can also be varied to adjust the temporal gap the substrates experiences between working electrodes.

References

{{Electroanalytical Electroanalytical methods

Structure

Distinction

See also

References