Transport of alkaline cation and neutral species through the alpha-Ni(OH)(2)/gamma-NiOOH film electrode

The transport of alkaline cation and neutral species through the alpha -Ni( OH)(2)/gamma -NiOOH film electrode has been investigated during the hydroge n extraction from and injection into the film electrode in 0.1 M LiOH, KOH and CsOH solutions by using the electrochemical quartz crystal microbalance technique combined with the potentiostatic current transient technique and cyclic voltammetry. From the ohmic relationship between the initial curren t density and the applied potential step, it is suggested that the hydrogen transport through the film electrode is exclusively governed by "cell-impe dance". On the basis of the "cell-impedance-controlled" hydrogen transport, the mass change measured indicates that during the hydrogen extraction, th e alkaline cation is slowly inserted into the film electrode before the fin ish of the current plateau. After the period of current plateau has finishe d, it is drastically inserted at an exponential rate. By contrast, during t he hydrogen injection, the extraction of alkaline cation is nearly complete d before the finish of the current plateau. Most of the neutral species are incorporated into the film electrode during the immersion prior to the hyd rogen extraction. The minority is not incorporated until the finish of the current plateau during the hydrogen injection.