of a coarsely porous sintering ceramic material for example based on al 2 o 3 or zro 2 that can be obtained by imprinting a corresponding paste or laminating on a porously sintering sheet its layer thickness is advantageously about 20 to 50 u03bcm as shown in fig1 it need not fill the entire area it is sufficient if parts of the oxygen diffusion path between the short circuit cell anode and the pumping cell cathode are constricted by a barrier the porosity of the diffusion barrier may be varied if required by the addition of pore formers which combust during the sintering process decompose or evaporate typical pore formers that can be employed are for example thermal soot powder graphite carbon plastics for example based on polyurethane salts for example ammonium carbonate and further organic substances such as for example theobromine and indanthrone such pore formers may be added to the porously sintering starting material in various quantities the electrodes of short circuit cell 5 and of pumping cell 9 are preferably composed of a metal of the platinum group particularly platinum or of alloys of metals of the platinum group or alloys of metals of the platinum group with other metals if required they contain a ceramic supporting frame material for example in the form of a ysz powder at a volume percentage of preferably about 40 volume percent they are porous and as thin as possible preferably they have a thickness of 8 to 15 u03bcm the conductor paths belonging to the electrodes are preferably also composed of platinum or a platinum alloy of the described type moreover they may likewise be produced from a paste based on a noble metal cermet solid electrolyte layer 8 is composed of one of the known.