On the mechanism of electrocatalytic oxygen reduction at metal chelates

Oxygen reduction reaction in acid medium at iron phthalocyanine dispersed on high surface area carbon substrate: tolerance to methanol, stability and kinetics

“…This result could lead to the conclusion that at least one step of the orr on FePc could modify the stability of the iron phthalocyanine molecule and cause its demetallation, but it was not possible to provide experimental evidence of this hypothesis. However, if one assumes that the adsorption step of oxygen at metallophthalocyanines occurs via an electron transfer from the central metal to the oxygen molecule [28,47,48], then the oxidation state of the iron atom increases from 2 to 3 which should lead to a decrease of the atomic radius of the central Fe [49]. Moreover, Stefan et al [50] showed, on the basis of EXAFS data, that the distance between the central Fe and a nitrogen in the FePc (d Fe-N(Pc) ) increased from 1.93 to 1.95-1.98 Å with FePc(H 2 O) and FePc + (H 2 O) 2 or FePc + (H 2 O) or (OH), respectively.…”

Molecular and Electronic Structures of Transition-Metal Macrocyclic Complexes as Related to Catalyzing Oxygen Reduction Reactions: A Density Functional Theory Study

“…It has been found that many TM macrocyclic complexes with N 4 -TM, N 2 O 2 -TM, N 2 S 2 -TM, O 4 -TM, and S 4 -TM structures, especially the N 4 -chelates (porphyrins, phthalocyanines, and tetraaza annulenes) of Fe and Co, exhibit measurable levels of catalytic activity for ORR . In alkaline solutions, the onset ORR potential of the FePc/C electrode was found to start at the same potential (0.050 V versus Hg/HgO) as that of the Pt/C electrode, and the ORR on the FePc/C electrodes proceeds mainly via a four electron pathway. − However, the catalytic performance of the FePc/C catalysts was, disappointingly, observed to deteriorate quickly in the catalyst durability test . As compared with the FePc/C catalyst, the CoPc/C electrode was shown to have a more negative onset ORR potential but better durability in electrochemical environments.…”

The Rational Design of Time‐Dependent (“Mechanical”) Homogeneous Catalysts. A Literature Survey of Multicentered Homogeneous Catalysis

“…Under normal conditions, 41 catalyzes the conversion of dioxygen to exclusively H 2 O 2 [94]. However, polymeric cobalt phthalocyanine 42 displays mixed product selectivity, generating about 50% H 2 O, along with H 2 O 2 under certain conditions [95]. The phthalocyanine structures in 41 and 42 are somewhat different, so that a simple comparison of this type may, of course, not be valid.…”