Electrochemical processes at electrified or polarized phase boundaries and methods for charging phase boundaries are discussed. An important type of interface, the three-phase junction, is introduced and processes at three-phase junctions are compared with those occurring at two-phase junctions. Finally, pairing charged interfaces is considered as a methodology for a more efficient use of electrical energy in microscale electrochemical processes. Chemical processes triggered by currents in the ultimate type of paired electrode system, a tunnel junction, are discussed.