Electrocatalytic activity carbon-supported metallophthalocyanine catalysts toward oxygen reduction reaction in alkaline solution

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Résumé

Carbon-supported metallophthalocyanine catalysts,
composed of a transition central metal M (M = Co, Mn, Ni,
Fe) in the phthalocyanine ring, were synthesized in this work.
As cathodic reaction in a fuel cell, the oxygen reduction reaction
(ORR) was investigated in alkaline medium with linear
scanning voltammetry at the surface of these electrocatalysts
deposited onto a rotating disk electrode (RDE). It was found
that the number of electrons transferred depended on the nature
of the metallic cation in the catalyst. Evidences provided
with Koutecky-Levich approach showed that iron phthalocyanine
(FePc) exhibited the better electrocatalytic ability toward
the ORR with four electrons exchanged and low activation
overpotential. Among these different as-prepared materials,
MnPc and FePc led to a four-electron pathway, while
CoPc and NiPc proceeded by a two-electron route. The latter
reaction process was also determined with a rotating ring-disk
electrode (RRDE), which allowed the determination of hydrogen
peroxide formed as O2 reduction intermediate in a small
amount, i.e., less than 1.2 %.

Mots-clés

Metallophthalocyanines . Cyclic voltammetry . Oxygen reduction reaction (ORR) . Electrocatalytic activity . Alkaline medium