Nonfaradaic processes

Nikolskii-Eisenman equation, 143 Nitric oxide, 121 Nonactin, 157 Nonfaradaic processes, 21 Normal pulse voltammetry, 67 Nucleic acids, 82, 185... 

NonFaradaic electrochemical modification of catalytic activity, NEMCA, see electrochemical promotion NonFaradaic processes, 2 Nyquist plot, 237... 

Electrode polarization is associated with a change in EDL charge density at the electrode surface. Other changes in surface state of the electrode are possible, too (e.g., the adsorption or desorption of different components, which also involve a consumption of electric charge). By convention, we describe this set of nonfaradaic processes as charging of the electrode surface. 

Nonfaradaic Processes and the Nature of the Electrode-Solution Interface 11... 

NONFARADAIC PROCESSES AND THE NATURE OF THE ELECTRODE-SOLUTION INTERFACE... 

Under some conditions an electrode may be in a potential region where charge-transfer reactions do not occur because they are either thermodynamically or kinet-ically unfavorable. However, such processes as adsorption can occur, and the structure of the electrode-solution interface can change, causing transitory changes in current and/or potential. These processes are called nonfaradaic processes. 

Only nonfaradaic processes occur at an ideally polarized electrode. 

Faradme Processes. Consider an ideally polarized electrode only nonfaradaic processes occur, no charges cross the interface, and no continuous current can flow. Upon addition of a substance that can be oxidized or reduced at the particular potential difference, current now flows—the electrode is depolarizedy and the substance responsible is called a depolarizer. 

One possible point of confusion regarding the notion of "cluster surface capacitance is also worthy of comment here. For electrode surfaces, capacitance charging is usually denoted as a nonfaradaic process to distinguish it from faradaic events that involve necessarily electron transfer across the metal-solution interface. From the cluster solutes, however, all charge build-up must necessarily occur via electron transfer from a source present in, or in contact with, the same solution (such as the gold electrode utilized in the spectroelectrochemical measurements). Of course, charging of plane metal surfaces may also occur by this faradaic mechanism, but is more conveniently achieved by connection to an external electrical source, thereby acting as a polarizable electrode. 

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