The possibilities are considered of applying the pulse potentiostatic method in measuring double-layer capacitance at the metal/solution interface, both for the practicahy perfectly polarizable mercury surface (with no electrochemical reaction taking place) and for solid metal electrodes, where it is not always possible to elimiite the effect of the faradaic current.
Short square potential pulses of small amplitude (10 mV) are superimposed over a preliminary set electrode potential, maintained potentiostatically. The i/f(t) curves obtained am then investigated. The quantity of electricity needed for charging the double layer is determined by graphical integration s t of Q = it dt.
The v&e C = 16.7 f 1-O ,~F/cm* has been obtained for the double-layer capacitance of mercury in @l N HCl, and C = 176 & 2.0 ,~F/crn* (visible surface) for smooth platinum in 1 N HsSO,. Measurements of double-layer capacitance of electrodeposited /?cobalt showed that if etching is performed in the anodic region and then the measurements in the cathodic region are repeated, the double layer capacitance is increased about 2.5 times.
Applying the pulse potentiostatic method, one may use the data on doublelayer capacitance to estimate the real reaction surface, when electrochemical investigations are carried out on large metal surfaces.