Reference electrodes Rotating ring-disk electrode

Figure 6.1 Schematic of a rotating ring-disk electrode. (For color version of this figure, the reader is referred to the online version of this book.)...

Bipotentiostat — An instrument that can control the potential of two independent -> working electrodes. A - reference electrode and an -> auxiliary electrode are also needed therefore the cell is of the four-electrode type. Bipotentiostats are most often employed in electrochemical work with rotating ring-disk electrodes and scanning electrochemical microscopes. They are also needed for monitoring the electrode-reaction products with probe electrodes that are independently polarized. All major producers of electrochemical equipment offer this type of potentiostat. The instruments that can control the potential of more than two working electrodes are called multipotentiostats. 

The inlaid disk and inlaid ring electrode can be combined to make an inlaid electrode in which the disk forms the interior which is surrounded by the ring. This is called a ring-disk electrode and when the entire assembly is rotated about its vertical axis it is referred to as a rotating ring-disk electrode (RRDE). Figure 4 illustrates a rotating disk electrode (RDE). 

In fact the ring-disk electrode is a combination of an ordinary rotating disk electrode (RDE) with a ring electrode. (The term ring electrode usually refers to the case where the region r-2 < r < rs is active with respect to the smface process r is the radius measured from the center of the cylindrical tip). This means that the regions 0 < r < a-2 and essential feature of this system is that there is an inactive region at the center of the disk.)... 

Figure 6.10 Current—potential curves at the disk electrode (below the x-axis in each figure) and the current at the ring electrode (Pt) (above the x-axis in each figure), recorded in Oa-saturated 1.0 mol dm KOH aqueous solution at different electrode-rotating rates. Disk electrode surface coated with a layer of (A) W2C/C, (B) Ag/C, (C) Ag-W2C/C, or (D) Pt/C. Potential scan rate 5 mV s ring potential fixed at 0.474 V vs Hg/HgO, and ring collection efficiency 20%. The insets present the Koutecky—Levich p ols of the disk electrode at different potentials. (For color version of this figure, the reader is referred to the online version of this book.)...

Cyclic voltammetry (CV), rotating disk electrode (RDE), and rotating ring-disk electrode (RRDE) in a traditional tri-electrode cell are often employed in the study of the ORR kinetics and mechanisms on various catalysts in liquid electrolytes [27, 28]. As shown in Fig. 15.2, a tri-electrode cell contains a working electrode (WE), a reference electrode (RE), and a counter electrode (CE). The CE has much... 

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