Metalloporphyrin Catalysts of Oxygen Reduction - Fuel Cell Catalysis: A Surface Science Approach - page 653

Figure 18.12 Chemical structures of selected simple Co porphyrins described in the text.

Co(Py 3 P), and tris-(4-cyanophenyl)-(N-methyl-4-pyridyl)porphyrin CoCP (Fig. 18.12),
in which the para-cyano groups were thought to coordinate to Ru II . Using
[Ru(edta)(OH 2 )] 2 as a source of Ru or using other porphyrins with coordinating
peripheral substituents (Fig. 18.12) did not produce catalysts superior to simple
Co porphyrins. However, exposing graphite-adsorbed Co(TPyP) to a solution of
[Os(NH 3 ) 5 (OH 2 )] 2 þ appears to have yielded an improved catalyst, and it was recently
reported that coordination of a single Pt complex to a Co porphyrin may also yield an
ORR catalyst with n av . 2 [Gadamsetti and Swavey, 2006]. The Co(TPyP) fragment
remains the most widely used porphyrin for studying the effect of peripheral metal
complexes on metalloporphyrin ORR catalysis [Araki and Toma, 2006].