Electrochemical reduction of oxygen at pyrolyzed iron and cobalt N4-chelates on carbon black supports

Besides platinum, various nonnoble metal compounds, when prepared appropria tely, are suitable for the electrochemical reduction of oxygen in liquid el ectrolytes and PEM-fuel cells. Pyrolyzed N4-chelates, such as phthalocyanin es, tetraazaannulenes and porphyrins with a central metal atom of iron or c obalt, are a very important group of compounds and have been investigated i n the past. It was found that the catalytic activity, especially of phthalo cyanines, was high when prepared on carbon black supports at high temperatu res (400-900 degrees C). Investigations on tetraazaannulenes and porphyrins yielded similar results. Non-noble metal compounds of cyclame (1,4,8,11-te traazacyclotetradecane), which are also N4-chelates, were not investigated as thoroughly. However, the catalytic activities of iron and cobalt cyclame s were low, compared to those of phthalocyanines. With the (GC-MS) analysis of both decomposition products, it could be shown that the mechanism of th e N4-chelate decomposition is of decisive importance for the catalytic acti vity.