Design and operational conditions of small electrochemical cell for optical switching employing hydrogenation of Pd/Y structure

A reversible optical transition in rare-earth metal hydrides can take place in a gas phase (when H2 is injected into the chamber with rare-earth metal film and pumped out periodically) as well as in an electrolyte solution (when the electrode of active metal is polarised cathodically and depolarised). The liquid hydrogenation process, though more reliable from technological point of view, still presents some undesirable side effects and inferior longevity due to high reactivity of metals and their hydrides towards electrolyte solutions and enhanced corrosion. In this paper, we present our results on electrochemical behaviour of the Y/Pd cathode and its reversible optical switching paying attention to some common problems that might affect the device work and even cause its destruction. Based on these data, we have discussed a possible design and optimum operational conditions of the planar electrochemical cell: type of electrolyte used in the cell (liquid, solid or polymeric); role and design of the anodic electrode and the anodic process accomplished on it; sealing problems due to the necessity to obtain a hermetically closed cell with a liquid electrolyte inside and a possible gas evolution under the operation.