Galvanostatic operation electrolysis

Constant current electrolysis is an easy way to operate an electrochemical cell. Usually, it is also applied in industrial scale electrolysis. For laboratory scale experiments, inexpensive power supplies for constant current operation are available (also a potentiostat normally can work in galvanostatic operation). The transferred charge can be calculated directly by multiplication of cell current and time (no integration is needed). 

For batch operation (see Sect. 2.3.4), the limiting current density is going to zero for increasing degree of conversion (see reactant 1 in Fig. 1). Here, the galvanostatic operation may only be acceptable if exclusively unproblematic side reactions occur, such as water electrolysis as solvent decomposition. In all other cases, better results can be expected using the potentiostatic operation (see next section). 

Working under galvanostatic conditions a is constant, and it is possible to identify two different operating regimes at a < 1 the electrolysis is controlled by the applied current, while at a > 1 it is controlled by the mass transport control. 

The electrochemical flow cell has also been used in combination with a UV spectrophotometer to obtain accurate UV spectra for a considerable number of aromatic radical anions (A ) in V,jV-dimethylformamide [65]. A solution of 0.1 mM of the aromatic compound (A) was pumped with a constant flow rate through the electrochemical flow cell. The latter was operated galvanostatically so that the electrolysis current could be increased steadily until the absorbance of the reduced or oxidized species attained a maximum, as illustrated in Figure 27. The maximum corresponds to the situation where all A is reduced to A (or to A + in the case of an oxidation). When the current is increased beyond the optimum value, a further reduction of A to A takes place, leading to the decrease observed in the absorbance of A . This may be accompanied by the appearance of the spectrum for A, as in... 

---