TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Metals: Metal M1 is a Group VIII transition metal, especially iron or ruthenium; metal M2 is a Group VIII transition metal, especially cobalt or iron. Preferred Additional Components: Additional carbonaceous components, preferably carbon black, may also be added to promote the formation of the carbon matrix.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Metal Complexes: Metal porphyrins, preferably containing cobalt or iron, especially cobalt or iron tetramethoxyphenyl-porphyrin.Preferred Chalcogen Compounds: Organic sulfur compounds, preferably thiourea.Preferred Method: An extra stage (before or after boiling the acid mixture) involves heating the catalyst powder material for 1 hour or more at high temperature (ca. 850degreesC) under inert atmosphere. Iron oxalate is used as precursor for the preparation of iron as the unsupported transition metal (M1). EXAMPLE - A mixture of 3.35 g iron(II) oxalate dihydrate, 0.65 g cobalt tetramethoxyphenylporphyrin and 0.18 g thiourea was heated for 2 hours at 450degreesC and 1 hour at 850degreesC, cooled, mixed under argon with 300 ml 1-N hydrochloric acid and boiled for 30 minutes. The mixture was then cooled and filtered, and the black powder obtained was washed with water and dried.    The various stages in this process were followed by thermogravimetric analysis, i.e. loss of water of crystallisation, formation of the isolated transition metal by decomposition of iron oxalate, formation of the carbon matrix and formation of the conductive sulfur bridge between iron and coordinated cobalt by decomposition of thiourea; this product already showed high activity in oxygen reduction and its activity was further increased by heating at 850degreesC. The product (I) showed specific capacity values of 100-300 F/g in electrochemical tests, indicating a porosity in the same order of magnitude as that of highly porous, commercial carbon black; this was confirmed by SEM analysis.    A mixture of 10 mg (I), 1 ml 0.2% ethanolic Nafion (RTM) solution and 1 ml water was subjected to ultrasound treatment for 3 minutes, then 5 micro-l of the suspension was placed on a polished vitreous carbon electrode (diameter 1 mm) and dried in air. This working electrode was tested in a 3-electrode cell with a mercury sulfate reference electrode, a platinum wire counter-electrode and 0.5-M sulfuric acid as electrolyte (oxygen-saturated solution), by plotting current density as a function of potential difference between working and counter electrodes, in comparison with a standard platinum catalyst (20% platinum on Vulcan XC 72R(RTM)). This gave voltage differences of 60, 40, 20 and 0 at 0.2, 2, 10 and 20 mA/cm2 respectively, indicating almost the same catalytic activity for catalyst (I) and the standard catalyst.