Abstract: A fuel cell device for generation of electricity from a polar oxidizer liquid and a non-polar fuel fluid includes a cathode in contact with the polar oxidizer liquid; an anode in contact with the non-polar fuel fluid; and a separator for separating the polar oxidizer liquid from the non-polar fuel fluid. The separator is made from material that is lyophobic with respect to the oxidizer liquid, and has a plurality of apertures, which are appropriately sized and spaced to form a meniscus in each aperture. The meniscus forms a liquid heterointerface between the conductive polar oxidizer liquid and the non-polar fuel fluid providing a controlled contact surface for oxidation processes. The fuel side of the separator may be coated with a conductive material to form the anode, in electric contact with the perimeter of the meniscus, and the cathode may be formed on the oxidizer side of the separator.