NOVELTY - The sintered gas or liquid diffusion electrode comprises a volumetrically compressed and structurally stable mixture of reactive metal particles having a high reactive surface area and metal substrate particles (226) having a lesser surface area than the reactive metal particles, and a current collector (222). A quantity of metal substrate particles is sufficient to provide structural stability to the electrode upon compression. The electrode is volumetrically compressed to a percentage of the mixture's original volume.    USE - The sintered gas or liquid diffusion electrode is useful in an electrochemical or catalytic application, an electrochemical sensor to detect an analyte capable of undergoing electrochemical reaction (all claimed), a fuel cell and an electrolysis device to generate hydrogen and oxygen.    ADVANTAGE - The sintered gas or liquid diffusion electrode has structural stability, and prevents the permeation of gases to avoid the mixture of hydrogen and oxygen gas.    DETAILED DESCRIPTION - The sintered gas or liquid diffusion electrode comprises a volumetrically compressed and structurally stable mixture of reactive metal particles having a high reactive surface area and metal substrate particles (226) having a lesser surface area than the reactive metal particles, and a current collector (222). A quantity of metal substrate particles is sufficient to provide structural stability to the electrode upon compression. The electrode is: volumetrically compressed to a percentage of the mixture's original volume to minimize volume while still permitting a sufficient amount of permeability to maintain a high catalytic efficiency; and configured to permit the flow of electricity. The current collector is embedded within the electrode. A portion of the reactive metal particles has a diameter of less than 10 nanometers, and comprises particles having an oxide shell. One face of the electrode has enhanced geometric surface area by adding contours. The surface area is contoured during volumetric compression. The sintering temperature is 400-700 degrees C.    DESCRIPTION OF DRAWING(S) - The diagram shows a schematic side view of an electrode.    Sintered electrode (220)    Current collector (222)    Compressed mixture (224)    Metal substrate particles (226)    Smaller reactive particles. (228)