Oxygen reduction catalysed by carbon supported iridium-chelates

Carbon supported iridium-octaethylporphyrin (IrOEP), iridium-tetraphenylporphyrin (IrTPP) and iridium-phthalocyanine (IrPc) were studied in acid for the oxygen redn. Both porphyrins give a four-electron redn., although a peculiar deactivation at low potentials occurs. At IrPc and heat-treated porphyrins hydrogen peroxide is formed. Results are compared with carbon monoxide oxidn. expts. at these catalysts. A single site mechanism is proposed for the oxygen redn. mechanism. [on SciFinder (R)