Commercial Instruments

There are several manufacturers of electrochemical equipment details of which are readily available directly from the manufacturers or from the web. An example of the 616 Rotating Disk Electrode manufactured by Princeton applied research is shown in figure 23. The electrode consists of a disk constructed from some conductive material (such as a noble metal or glassy carbon), which is mounted in a nonconductive polymer and fitted with an axle that can be rotated by a suitable motor. As the disk rotates in the ionic solution, the solution in contact with the disk (the hydrodynamic boundary layer) is dragged by the spinning motion to the periphery of the disk and solution. The surface liquid that is removed by this process is continually replaced by a flow, perpendicular to the disk, from the bulk solution. As a result there is a constant lamina flow of liquid across the surface of the disk and the liquid in contact with the surface is continually renewed. The rate of hydrodynamic boundary layer replacement is controlled by the angular velocity of the disk (the rotational speed of the disk).

Figure 23. The 616 Rotating Disk Electrode

Thus, the flow quickly achieves a situation where the steady state current is no longer controlled by diffusion but by the solution flow. This device is employed in linear sweep voltammetry and many other electrochemical phenomena.