Porphyrins, fuel cell oxygen reduction

The development of such a reaction proceeding under mild conditions is a technological challenge constituting one of the key points for the finalizing of efficient and low cost fuel cells. The catalytic properties of macrocyclic complexes like porphyrins and phthalocyanines for the reduction of molecular oxygen have been well known for four decades350,351 and numerous papers are devoted to this area. Here only some relevant and recent work in this field is described. 

Most of the catalysts employed in PEM and direct methanol fuel cells, DMFCs, are based on Pt, as discussed above. However, when used as cathode catalysts in DMFCs, Pt containing catalysts can become poisoned by methanol that crosses over from the anode. Thus, considerable effort has been invested in the search for both methanol resistant membranes and cathode catalysts that are tolerant to methanol. Two classes of catalysts have been shown to exhibit oxygen reduction catalysis and methanol resistance, ruthenium chalcogen based catalysts " " and metal macrocycle complexes, such as porphyrins or phthalocyanines. ... 

Faubert, G. et al.. Iron catalysts prepared by high-temperature pyrolysis of tetraphenyl-porphyrins adsorbed on carbon black for oxygen reduction in polymer electrolyte fuel cells, Electrochim. Acta, 43, 341, 1998. 

Cobalt porphyrins and phthalocyanines were used as precursors for preparation of carbon supported cobalt catalysts that displayed high activity in reduction of oxygen in fuel cells [9-12], These samples were prepared by deposition of cobalt phtalocyanine on active carbon following by heat treatment at 650-700°C in an inert atmosphere providing formation of Co-N structure deposited on active carbon. 

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