ESCA AND ELECTROCHEMICAL STUDIES ON PYROLYZED IRON AND COBALT TETRAPHENYLPORPHYRINS

Catalysts for the reduction of O2 have been prepared by pyrolysis of CoTPP and FeClTPP in their crystalline state as well as in different mixtures with carbon black. ESCA measurements on these pyrolysed porphyrins have been correlated to their catalytic properties. When porphyrins are pyrolysed with carbon black, sublimed chelates re-adsorb on the surface of carbon black forming a stable chelate-carbon support bond, which is believed to increase the activity and stability of the catalyst. Porphyrins pyrolysed without carbon black become electrically conducting after pyrolysis as a result of a polymerization reaction with the chelates intact. For porphyrins pyrolysed without carbon black the main active site is believed to be a metal chelate but for the Co-catalyst there is evidence that other surface components, formed as a result of decomposition of the chelate, influence the activity.