Electron movement during electrode

During reduction, electrons travel/rom the power pack, through the electrode, transfer across the electrode-solution interface and enter into the electroactive species in solution. Conversely, during oxidation, electrons move in the opposite direction, and are conducted away from the electroactive material in solution and across the electrode-solution interface as soon as the electron-transfer reaction occurs. (Incidentally, these different directions of electron movement explains why an oxidative current has the opposite sign to a reductive current, cf. Section 1.2.)... 

Electron movement through the electrode. The movement of electrons through an electrode will usually be extremely fast since the material from which the vast majority of electrodes are made will have been chosen by the analyst precisely because of its superior electronic conductivity. Electrodes made of liquid mercury and of solid metals such as platinum, gold, silver or stainless steel, are all used for this reason. Accordingly, it is extremely unlikely that the rate-limiting process during a redox reaction will be movement of the electrons through the electrode. 

A battery operates on the principle of a Galvanic cell a chemical reaction is used to produce electricity. The materials that are involved in the reaction form the electrodes and the reaction takes place by the passage of ions through an electrolyte. The formation of ions during the chemical reaction involves the transfer of electrons to or from the electrodes. In a galvanic cell these are not allowed to pass through the electrolyte but must travel around an external circuit, driven by a potential difference created between the electrodes. It is the electron movement through the external circuit that can be used to do work. 

In cyclic voltammetry, both the oxidation and reduction of the metal complex (called the analyte from now on) will take place in one electrochemical cell. This cell houses the analyte solution as well as three electrodes, the working electrode, the auxiliary electrode and the reference electrode. Electron transfer to and from the metal complex takes place at the working electrode surface (Fig. A.2.2) and does so in response to an applied potential, /iapp, at the electrode surface. During the experiment, current develops at the surface as a result of the movement of analyte to and from the electrode as the system strives to maintain the appropriate concentration ratio (0, through electron transfer, as specified by the Nemst equation. 

Reported studies include various deposition and dissolution processes [876,908] and mechanistic studies of electrode processes at redox-active polymer-coated surfaces [909-912]. In a typical study of a polymer film containing ruthenium ions as redox-active centers, a cyclic voltammogram indicative of the one electron transfer at this center is observed as depicted in Fig. 5.144. The movement of ions needed for charge compensation in the film after a change of the redox state can be detected with PBD. The positive-going response during oxidation of the ruthenium center... 

Once a very electroactive material was developed, the next challenge was how to keep an actuator electronically wired using these types of dynamic materials. Keeping the electrodes placed in the EAP during movement is an extreme challenge because when the EAPs undergo motion the electrodes that are attached to them, even if embedded, can become detached from the EAPs, which causes actuator failure. Plasma treatment and other metal treatments were investigated to improve the interface between the EAP and the embedded electrodes. 

A voltaic cell consists of a silver—silvCT ion half-cell and a nickel—nickel(II) ion half-cell. Silver ion is reduced during operation of the cell. Sketch the cell, labeling the anode and cathode and indicating the corresponding electrode reactions. Show the direction of electron flow in the external circuit and the direction of cation movement in the half-cells. 

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