One of the most common applications of an electrochemical etching cell is the preparation of a Nanocrystalline Porous Silicon Layer on a single crystal Si wafer. 

Application note
To perform an electrochemical process, a square conducting sample is placed on the cell base, using a piece of aluminum foil as a back contact. The setup is sealed by an O-ring to prevent electrolyte leakage. The cell is filled with an electrolyte, and the wire electrode is immersed in the solution as a counter electrode. An electric current is passed between the aluminum back contact and the wire electrode for a certain amount of time. After the process, the cell elements should be washed several times with ethanol and dried under the nitrogen flow. See the assembly demonstration here.

Material:
PEEK
PTFE