BASIC POTENTIAL STEP METHODS

The next three chapters are concerned with methods in which the electrode potential is forced to adhere to a known program. The potential may be held constant or may be varied with time in a predetermined manner as the current is measured as a function of time or potential. In this chapter, we will consider systems in which the mass transport of electroactive species occurs only by diffusion. Also, we will restrict our view to methods involving only step-functional changes in the working electrode potential. This family of techniques is the largest single group, and it contains some of the most powerful experimental approaches available to electrochemistry. 

the electrode must reduce the nearby anthracene to the stable anion radical  

This event requires a very large current, because it occurs instantly. Current flows subsequently to maintain the fully reduced condition at the electrode surface. The initial reduction has created a concentration gradient that in turn produces a continuing flux of anthracene to the electrode surface. Since this arriving material cannot coexist with the electrode at E2, it must be eliminated by reduction. The flux of anthracene, hence the cur- 

This experiment, called double potential step chronoamperometry, is our first example of a reversal technique. Such methods comprise a large class of approaches, all featuring an initial generation of an electrolytic product, then a reversal of electrolysis so that the first product is examined electrolytically in a direct fashion. Reversal methods make up a powerful arsenal for studies of complex electrode reactions, and we will have much to say about them. 

Of course, one could also record the derivative of the current v. time or potential, but derivative techniques are rarely used because they intrinsically enhance noise on the signal (Chapter 15). 

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Chapter 5. Basic Potential Step Methods TABLE 5.3.1 Form of hiq for UMEs of Different Geometries... 

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