NOVELTY - An air cathode has a multiple-layered structure comprising at least a base material layer, two sintered diffusion layers and a sintered activation layer that are arranged into a laminating shaped structure. The base material made of metal wire net or metal foam net is served as an electric current collector having upper and bottom sides carrying a sintered diffusion layer made of hydrophobic carbon material.    USE - For use as a cathode of a zinc/air cell, a fuel cell or an electric capacitor. (Claimed)    ADVANTAGE - The cathode possesses the effect of preventing the electrolytic solution inside the zinc/air cell from being affected by the environment air. It effective achieves the purpose of decreasing the amount of water passing through the multiple-layered structure. It avoids the interference on the electrolytic solution by the environmental air outside the cell. It effectively solves the problem of unable to maintain the water content in a normal condition for longer period, particularly the water content of zinc anode of the zinc/air cell can be maintained in the normal condition for over 1 month. It enables the zinc/air cell to maintain stable electric property for a longer period under dry environmental condition.    DETAILED DESCRIPTION - An air cathode has a multiple-layered structure comprising at least a base material layer, two sintered diffusion layers and a sintered activation layer that are arranged into a laminating shaped structure. The base material made of metal wire net or metal foam net is served as an electric current collector particularly having both of its upper and bottom sides carrying a sintered diffusion layer made of hydrophobic carbon material. One of the sintered diffusion layers carries the sintered activation layer that is arranged on an outer side of the sintered diffusion layer made of hydrophilic carbon material carrying a transition metal oxide catalyst.    An INDEPENDENT CLAIM is also included for a process of producing an air cathode, comprising:    (i) making an electric current collector of a zinc/air cell by using metal foam net or metal wire net;    (ii) mixing a hydrophobic carbon powder or carbon material of acetylene-reduced carbon black or coking carbon black, polytetrafluoroethylene (PTFE) aqueous suspension binder and deionized water in the proportion of 2:1:50 or 3:1:50, then having the mixture of PTFE binder and hydrophobic carbon powder undergo heat drying process, then, after completion of heat drying process, coating both upper and bottom sides of a base material obtained in the making step with the mixture of PTFE and hydrophobic carbon powder to form a sintered diffusion layer, then applying high pressure to make the carbon powder tightly bound together and heating the base material carrying a hydrophobic carbon powder at 200-400degreesC for 20-40 minutes to sinter the mixture of PTFE binder and hydrophobic carbon powder into a rigid carbon powder with a net-shaped structure to form the sintered diffusion layer of the air cathode, and then adjusting the thickness of the sintered diffusion layer by a roller press machine; and    (iii) mixing the hydrophobic carbon powder or carbon material of acetylene-reduced carbon black or coking carbon black, nanometer carbon tube or nanometer carbon horn, PTFE binder and transition metal oxide catalyst powder in the proportion of 4:1:1 or 3:1:2, then adding water, methyl alcohol or isopropyl alcohol to the mixture as a solvent to form uniformly mixed size, then coating the surface of the sintered diffusion layer on the upper side of the base material with the mixed size by a spray gun or other coating method to form a sintered activation layer, then heating the base material carrying the sintered diffusion layer and the sintered activation layer at 200-400degreesC for 10-60 minutes to sinter the mixture of PTFE binder, the transition metal oxide catalyst powder and the hydrophobic carbon powder to form a rigid-type carbon powder carrying the transition metal oxide catalyst powder to form the sintered activation layer of the air cathode, and then adjusting the thickness of sintered activation layer using the roller press machine to form the air cathode having the laminating shaped multiple layer sintering structure.    DESCRIPTION OF DRAWING(S) - The figure is a manufacturing process flow diagram of an air cathode.