Voltammetry galvanostatic

Faraday s law (p. 496) galvanostat (p. 464) glass electrode (p. 477) hanging mercury drop electrode (p. 509) hydrodynamic voltammetry (p. 513) indicator electrode (p. 462) ionophore (p. 482) ion-selective electrode (p. 475) liquid-based ion-selective electrode (p. 482) liquid junction potential (p. 470) mass transport (p. 511) mediator (p. 500) membrane potential (p. 475) migration (p. 512) nonfaradaic current (p. 512)... 

Although it is not necessary, the galvanostat-potentiostat is better to incorporate a function generator in order to allow for cyclic voltammetry or other transient electrochemical techniques. 

Fig. 11. Cyclic voltammetry of first discharging/charging of galvanostatically prepared PPy films (PC, 0.5 M LiC104) the first three cycles between +0.5 V and —0.3 V, the following between +0.5 V and —1.1 V...

For the individual types of transient measuring techniques, special names exist but their terminology lacks uniformity. The potentiostatic techniques where the time-dependent current variation is determined are often called chronoamperometric, and the galvanostatic techniques where the potential variation is determined are called chronopotentiometric. For the potentiodynamic method involving linear potential scans, the term voltammetry is used, but this term is often used for other transient methods as well. 

Table 3. Capacitance values (F g1) of the KOH activated carbons (A-C A-CS A-PM A-PS A-AC) estimated by galvanostatic discharge, cyclic voltammetry and impedance spectroscopy. ecific ca acitancejiF m alculated erjurfdceareao carbon.

Sample Galvanostatic discharge C/Fg1 Cyclic voltammetry C/Fg1 Impedance spectroscopy C/Fg1 Specific capacitance uF cm 2... 

Polyaniline (PANI) was investigated as electrocatalyst for the oxygen reduction reaction in the acidic and neutral solutions. Galvanostatic discharge tests and cyclic voltammetry of catalytic electrodes based on polyaniline in oxygen-saturated electrolytes indicate that polyaniline catalyzes two-electron reduction of molecular oxygen to H2O2 and HO2". 

Detection of Li+ in artificial serum with a voltammetric Li-selective electrode in a flowthrough system was demonstrated [64], Lithium salts such as lithium carbonate have been extensively used for treatment of manic depressive and hyperthyroidism disorders. The therapeutic range of Li concentration is generally accepted to be 0.5-1.5mM in blood serum. The authors used normal pulse voltammetry in which a stripping potential was applied between pulses in order to renew the membrane surface and expel all of the extracted ions from the membrane, similar to galvanostatically controlled potentiometric sensors described above. Unfortunately, the insufficient selectivity... 

The observed small and interconnected pores are expected to perform as electrodes of supercapacitors. Cyclic voltammetry (CV) and galvanostatic charge/discharge curves were used to characterize the capacitive properties the resulting data in simple acid (1 mol L 1 II2S0/() are shown in Fig. 7.11. 

Potential Sweep Method, In the transient techniques described above, a set of measurements of the potential for a given current or the current for a given potential is measured in order to construct the current-potential function, i = f(E). For example, the Tafel lines shown in Figure 6.20 were constructed from a set of galvanostatic transients of the type shown in Figure 6.18. In the potential sweep technique, i = f(E), curves are recorded directly in a single experiment. This is achieved by sweeping the potential with time. In linear sweep voltammetry, the potential of the test electrode is varied linearly with time (Fig. 6.23a). If the sweep rate is... 

Potentiostat/galvanostat (Hokuto Denko, HZ-3000) for cyclic voltammetry. 

Apparatus Cyclic voltammetry and amperometric current-time curves were obtained with a Pine Instrument Inc., Model RDE4 bipotentiostat and Kipp Zonen BD 91 XYY recorder equipped with a time base module. All measurements were performed in a conventional single-compartment cell with a saturated calomel electrode as the reference electrode and a Pt mesh as the auxiliary electrode at room temperature. Chronoamperometry was made with EG G Princeton Applied Research potentiostat/galvanostat Model 273 equipped with Model 270 Electrochemical Analysis Software. 

The most common techniques for testing electrodes are sweep voltammetry, galvanostatic poten-tiometry, rotating disk electrochemistry, and impedance spectroscopy. Detailed information about these techniques may be found in most classical electrochemical textbooks [6-13], and we will present here the basics of these techniques. 

This method is one of the most used to characterize active masses. It quickly provides useful information about potential range of activity, capacity, cyclability, and kinetics. The result is a current versus potential (or versus time). Sweep voltammetry is easily conducted with commercially available potentiostat-galvanostat. Common sweep rates are in the range of 0.001-100 mV/s and common current densities from 0.01 to 10mA/cm2. Cyclic voltammetry is usually applied for estimating the reversibility of the electrochemical reaction. 

If the reference electrode is correctly placed in the same equipotential as the working electrode, ohmic drop in the electrolyte may be negligible, but this may not be the situation in the bulk of the electrode. Quantitative determination of the electrode resistance is difficult when using voltammetry only. It is much easier using galvanostatic cycling. 

Although electrochemical characterizations have recently been performed on single intercalation particles, in most cases composite powdery electrodes containing a mixture of intercalation particles, electrically conductive additives (e.g., carbon black) and PVDF binder have also been used. In order to obtain consistent results and to reach comprehensible intercalation mechanisms in these electrodes, basic electroanalytical characterizations such as slow-scan rate -> cyclic voltammetry (SSCV), -> potentiostatic intermittent titration (PITT) (or -> galvanostatic intermittent titration, GITT), and -> electrochemical impedance spectroscopy (EIS) should be applied in parallel or in a single study. 

---