An energy storage device comprises a first porous semiconducting structure (510) comprising a first plurality of channels (511) that contain a first electrolyte (514) and a second porous semiconducting structure (520) comprising a second plurality of channels (521) that contain a second electrolyte (524). In one embodiment, the energy storage device further comprises a film (535) on at least one of the first and second porous semiconducting structures, the film comprising a material capable of exhibiting reversible electron transfer reactions. In another embodiment, at least one of the first and second electrolytes contains a plurality of metal ions. In another embodiment, the first and second electrolytes, taken together, comprise a redox system.