Oxygen Binding to Cobalt and Iron Phthalocyanines As Determined from in Situ X-ray Absorption Spectroscopy

Cobalt phthalocyanine (CoPc) and iron phthalocyanine (FePc) are possible oxygen reduction catalysts in fuel cells, but the exact functioning and deactivation of these catalysts is unknown. The electronic structure of the CoPc and FePc has been studied in situ under hydrogen and oxygen atmospheres by a combination of ambient-pressure X-ray photoelectron spectroscopy and X-ray absorption spectroscopy. The results show that when oxygen is introduced, the iron changes oxidation state while the cobalt does not. The data show that oxygen binds in an end-on configuration in CoPc, while for FePc side-on binding is most likely.