An electrochemical measuring electrode device (10) for polarographically measuring the partial pressure of oxygen in an electrolytic medium comprises a cathode (14) which is capable of reducing oxygen and defines an exposed oxygen-reducing cathode surface (20), an anode (18), which defines an exposed anode surface which is arranged relative to the exposed oxygen-reducing cathode surface so as to communicate electrolytically therewith through the electrolytic medium, and a membrane (24), which covers the exposed oxygen-reducing cathode surface and further defines an electrolyte chamber (22) in which the electrolytic medium is confined. In order to effectively promote the decomposition of H.sub.2 O.sub.2 generated in the electrolytic medium as an oxygen reduction intermediate and thereby reduce the response time of the electrode, a stable, non-biological catalytic means is provided catalytically communicating with the H.sub.2O 2. The stable, non-biological catalytic means is preferably constituted by platinum black particles which may be received by the membrane at a central region (42) thereof or alternatively be received by a support structure which may further constitute a covering of at least part of the membrane (24).The platinum black particles may be pressed into a foil material constituting a base material of the membrane or alternatively be applied in a suspension to the membrane whereupon the suspension is solidified.