The electrochemical behavior of a conductive carbon-rich fluorine-doped tin oxide (CFTO) powder synthesized via the sol–gel process was investigated by studying the chloride oxidation reaction in aqueous media with the help of a cavity microelectrode (CME) without any binding additive. This new electroactive compound was found to be very efficient with respect to the chloride–chlorine reaction which was reversible in the 2–7 pH range. The CFTO powder electrode was characterized by linear sweep voltamperometry and electrochemical impedance measurements. On the basis of numerical simulations, impedance spectra were interpreted by considering a porous electrode behavior with a coupled concentration and potential axial gradients. The experimental data were quantitatively accounted for by considering the parallel combination of a number of cylindrical pores. On the CFTO powder, the chloride oxidation mechanism was simply described by a single electron exchange, in accordance with a Volmer–Tafel mechanism.