Working electrodes configuration

ASTM G5 describes a procedure for a potentiodynamic polarization test on type 430 stainless steel in sulfuric acid that is intended to be a means to check experimental technique and instrumentation [2]. It indicates that the multinecked flask shown in Fig. 2(a) and the electrode configuration shown in Fig. 1(f) are suitable for the cell and working electrode configuration, respectively. A scan rate of 0.167 mV s is specified. 

A schematic of the working electrode configuration is shown in Fig. 12. The radius of the quartz disk, Tq, is 1/2 inch the thickness, dq, is 1/8 inch. A thin layer of titanium ( 5 x 10 cm) is vapor deposited on the quartz disk followed by deposition of the desired thickness, of gold (generally 10 cm where noted 0.3 x 10 " cm). The radius of the deposited gold layer, r, is 1.1 cm the radius of the exposed electrode, /- , is 0.475 cm. Details of the preparation of the gold electrode are presented in Sec. V.B. The entire assembly is held together with a simple clamp (not shown in Fig. 12). 

Single, dual, and even triple working electrode configurations for determination of cysteine- and cystine-containing peptides (e.g., glutathione) have been used with HPLC [39,53,61-65,75-89,91-93,95-105,109] or CE [46,90,92,106,... 

The solution to reference electrode instabiUty is the introduction of a third or auxiUary electrode. This particular electrode is intended to carry whatever current is required to keep the potential difference between the working and reference electrodes at a specified value, and virtually all potentiostats (instmments designed specifically for electrochemistry) have this three-electrode configuration. Its use is illustrated in Figure 3. 

The value of Eff is affected by many experimental conditions other than the electrolyte and anode materials. The experimental conditions include such factors as the cell configuration, electrode orientation, electrode surface area, working electrode substrate, charge-discharge currents, charge quantity, and amount of electrolyte. 

FIGURE 3-22 Coimnon detector configurations (a) thin-layer (channel) and (b) wall-jet flow cells. WE = working electrode. 

Both cell designs permit positioning of the second electrode downstream of the first working electrode (Fig. 11), which is known as the series configuration. This electrochemical transducer is used in the same manner as the classic ring-disk electrode. Products generated at the upstream electrode are detected (or collected) at the downstream electrode Selectivity is enhanced when the products of the upstream... 

The necessary thin-layer configuration was obtained by pressing the electrode against the optical window. Different cell constructions have been used. Fig. 1.6 shows a cell similar to one used by Seki et al. [32], The micrometer screw attached to the working electrode allows a reproducible adjustment of electrode-window distances. 

Most recently, they have developed" a cell configuration for the study of modified electrodes that employs, as a working electrode, colloidal graphite deposited onto kapton tape (typically employed as a window material). Such an arrangement minimizes attenuation due to the electrolyte solution. 

It should be stressed that the field-ions related measurements are still of a very preliminary nature. Work is in progress both on determining the fundamental electrical properties of the radon progeny and based on this on the influence on progeny removal of electrode configuration etc. 

Three main electrode configurations have been used in ECL work rotating ring-disk (RRD), dual and single electrodes. With the RRD electrode, the disk may,... 

Cu, In, Ga, and Se are codeposited from the solution at room temperature in a three-electrode cell configuration, where the reference electrode is a platinum pseudo-reference, the counter electrode is platinum gauze, and the working electrode is the substrate. The substrates typically used are glass, DC-sputtered with about 1 pm of Mo. In all experiments, the applied potential is -1.0V versus the Pt pseudo-reference electrode. The corresponding current density range for the deposition is 5 to 7 mA/cm2. 

The counter electrode is the current carrying electrode and it must be inert and larger in dimension. Platinum wire or foil is the most common counter electrode. For work with micro- or ultramicroelectrode where the maximum current demand is of the order of few microamperes, the counter electrode is not necessary. At very low current, a two-electrode system with the reference electrode can function as the current-carrying electrode with very little change in the composition of the reference electrode. Many commercial glucose sensors and on-chip microcells have such electrode configuration. 

The well-jet electrode can have many different configurations, but it is usually flat and circular. Figure 7.8(b) shows the pattern of solution flow during operation, from which it is easy to see why back splashes are carried away by the flow before they can reach the working electrode. 

---