The use of ZrO2 membrane on counter electrodes (e.g. Zr) is proposed for controlling the mass transfer rates to the electrode and therefore the extent of possible loss reactions. A comparative study was undertaken to examine the influence of the prepn. technique of the Zr/ZrO2 electrode on its electrochem. properties using the Ce(IV)/Ce(III) redox couple as test reaction. The obtained results showed that the rate of Ce(IV) redn. is strongly decreased on Zr/ZrO2 cathodes, prepd. by the thermal oxidn. of metallic Zr. A model is also proposed for the quasi-divided operation mode, where the counter electrode is covered with an inorg. membrane (ZrO2). Such electrochem. reactors offer an effective alternative to the traditional divided electrochem. reactor. [on SciFinder (R)]