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An ordered network of tetrasodium tetra(4-sulphonatophenyl)porphyrin iron(III) chloride (FeTPPS 4 Na 4 ), which exhibited a higher catalytic activity for oxygen reduction than Co and Ir(CO)TPPS 4 Na 4 , was fabricated by complexation with alkaline-earth metal ions. Heat treatment of these complexes enhanced their catalytic activity with the 2 highest performance observed with Ba 2+ -FeTPPS 4 . The onset potential for oxygen reduction (E onset ) was 720 mV vs. Ag|AgCl, which is almost the same as that for Pt-impregnated carbon black. The number of electrons, n, transferred during oxygen reduction at a Ba 2+ -FeTPPS 4 -coated electrode, as determined by rotating ring-disc experiments, was 3.9 and suggests that oxygen was reduced to water. A neutral solution of FeTPPS 4 Na 4 was acidified by the addition of barium ion, and the elemental ratio

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