The electrodes are typically separated by a thin porous foil (with a thickness between 0.050 to 0.5 mm), commonly referred to as diaphragm or separator. The diaphragm is non-conductive to electrons, thus avoiding electrical shorts between the electrodes while allowing small distances between the electrodes. The ionic conductivity is supplied by the aqueous alkaline solution, which penetrates in the pores of the diaphragm. The state-of-the-art diaphragm is Zirfon, a composite material of zirconia and Polysulfone. The diaphragm further avoids the mixing of the produced hydrogen and oxygen at the cathode and anode, respectively. 
Typically, Nickel based metals are used as the electrodes for alkaline water electrolysis.  Considering pure metals, Ni is the least active non-noble metal. The high price of good noble metal electrocatalysts such as platinum group metals and their dissolution during the oxygen evolution is a drawback. Ni is considered as more stable during the oxygen evolution, but stainless steel has shown good stability and better catalytic activity than Ni at high temperatures during the Oxygen Evolution Reaction (OER).
High surface area Ni catalysts can be achieved by dealloying of Nickel-Zinc or Nickel-Aluminium alloys in alkaline solution, commonly referred to as Raney nickel. In cell tests the best performing electrodes thus far reported consisted of plasma vacuum sprayed Ni alloys on Ni meshes
and hot dip galvanized Ni meshes. The latter approach might be interesting for large scale industrial manufacturing as it is cheap and easily scalable, but unfortunately, all the strategies show some degradation.