An apparatus including a housing having walls is provided. The walls of the housing each have inner surfaces and outer surfaces. The walls may include apertures extending from the inner surface to the outer surface. The inner surfaces of the walls define a volume. The volume includes an electrode. The volume further includes a water-controlling separator disposed between the inner surface of the housing and the electrode. The water-controlling separator can block a flow of liquid from the electrode through the apertures to the ambient environment while allowing oxidant to flow from the ambient environment through the apertures to the electrode.