Abstract: An apparatus having a percolating, sponge-like nanoparticulate layer, the apparatus being suitable for numerous technical applications. The object is accomplished by an apparatus having an electrode and a sponge-like, percolating, electrically-conductive layer comprising bound nanoparticles, the layer containing cavities and at least partially covering the electrode. The size of the nanoparticles is at most 15 times the size of a forming space-charge region in the layer; the cavities in the layer are at least partially filled with an electrolyte. The cavities of the layer are larger than the space-charge region in the electrolyte. The electrolyte also forms a film, which borders the surface of the layer located opposite the electrode. The apparatus also includes elements with which a voltage can be applied between the electrode and the electrolyte.