Noncovalent Immobilization of a Pyrene-Modified Cobalt Corrole on Carbon Supports for Enhanced Electrocatalytic Oxygen Reduction and Oxygen Evolution in Aqueous Solutions

Efficient
oxygen evolution reaction (OER) and oxygen reduction
reaction (ORR) are the determinants of the realization of a hydrogen-based
society, as sluggish OER and ORR are the bottlenecks for the production
and utilization of H2, respectively. A Co complex of 5,15-bis­(pentafluorophenyl)-10-(4)-(1-pyrenyl)­phenylcorrole
(1) bearing a pyrene substituent was synthesized. When
it was immobilized on multiwalled carbon nanotubes (MWCNTs), the 1/MWCNT composite displayed very high electrocatalytic activity
and durability for both OER and ORR in aqueous solutions: it catalyzed
a direct four-electron reduction of O2 to H2O in 0.5 M H2SO4 with an onset potential of
0.75 V vs normal hydrogen electrode (NHE), and it catalyzed the oxidation
of water to O2 in neutral aqueous solution with an onset
potential of 1.15 V (vs NHE, η = 330 mV). Control studies using
a Co complex of 5,10,15-tris­(pentafluorophenyl)­corrole (2) demonstrated that the enhanced catalytic performance of 1 was due to the strong noncovalent π–π interactions
between its pyrene moiety and MWCNTs, which were considered to facilitate
the fast electron transfer from the electrode to 1 and
also to increase the adhesion of 1 on carbon supports.
The noncovalent immobilization of molecular complexes on carbon supports
through strong π–π interactions appears to be a
simple and straightforward strategy to prepare highly efficient electrocatalytic
materials.