Cybernetic Control of an Electrochemical Repertoire (Potentiostat, Instrumentation, Adsorption)
He, Peixin
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https://hdl.handle.net/2142/70300
Description
Title
Cybernetic Control of an Electrochemical Repertoire (Potentiostat, Instrumentation, Adsorption)
Author(s)
He, Peixin
Issue Date
1985
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Chemistry, Analytical
Abstract
Many experimental methods have been developed to attack different problems by electrochemical means. In chemical analysis, sensitivity and selectivity may be achieved by using different methods. The availability of multiple techniques is even more important in fundamental research. Diagnostic conclusions usually can be drawn only after observations from many different angles.
This thesis describes the design and application of a cybernetic potentiostat. Over twenty different electrochemical methods have been implemented in its electrochemical repertoire. The system also supplies extremely flexible control and a variety of data processing and display functions. The hardware comprises a potentiostat, a computer system, and some proper interfaces. All function generation, data acquisition and signal processing steps are accomplished by software.
An important feature of the instrument is a provision for automatic compensation of cell resistance. Through software, the system first makes an actual measurement of uncompensated resistance in the cell; then it decides the maximum degree of compensation that can be prudently attained by positive feedback. The decision is made on the basis of a stability test of the potentiostat system. Stabilizing elements can also be switched into the feedback loop if necessary. The potentiostat is never allowed to break into oscillation; nonetheless, full compensation is often possible.
An example of the application of the cybernetic potentiostat in electrochemical research is the study of adsorption of sulfonated anthraquinones (AQS) at a mercury electrode. The adsorption behavior of AQS has been carefully examined. A noticeable phenomenon is an extremely sharp and narrow current spike which is superimposed on the adsorption prewave. It is believed that the spike originates from the stabilization of the adsorbed product, after the reorganization of the adsorbed species on the surface of the electrode at a favorable potential. The stabilization may be due to intermolecular hydrogen bonding between hydroquinone groups and sulfonate groups.
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