ISSN:
1089-7623
Source:
AIP Digital Archive
Topics:
Physics
,
Electrical Engineering, Measurement and Control Technology
Notes:
Electrical behavior of the ideally polarizable metal–solution interface is similar to a RC series circuit. The dc polarization, E, of the interface is potentiostatically controlled and differential capacity, C, measurements are carried out with a linear variation of E versus time. A precise measurement method of C is described in the case where the time constant of the circuit is rather high ((approximate)10−2 s). The principle of this method is to impose on the interface an ac current perturbation, Iω, and to measure the ac potential response, Eω. A system composed of a low bandwidth potentiostat (〈1 Hz) and a galvanostat controls the dc potential, E, and produces the ac current, Iω. In- and out-of-phase components of the ac potential response, Eω, are analyzed by means of a lock-in amplifier. An ohmic drop compensation technique with suppression of the residual common mode is used to improve the determination of the Eω(90°). Using a dummy cell, comparison between the new method and the classic potentiostatic technique is carried out. Results show that it is possible to measure C with a relative error less than 1% in a frequency range up to 2 kHz whereas with the classic potentiostatic technique the frequency range is limited to around 100 Hz. © 1998 American Institute of Physics.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1063/1.1149051
Permalink