Four β-pyrrole-substituted cobalt(iii) corroles were studied as electrocatalysts for the oxygen reduction reaction. The results disclose high dependence of the corrole's performance on its substituents, but once adsorbed on a high surface area carbon, this effect vanishes, resulting in a better catalytic performance than most well-defined molecular electrocatalysts for this reaction.
Bioinspired transition-metal complexes may serve as efficient
and low-cost potential catalysts for oxygen reduction reaction (ORR)
in fuel cells, instead of precious group metal-free (PGM-free) materials.
Herein, we present a study of the ORR electrocatalytic activity of
different mesosubstituted Co-corroles with varying electronegativity
using both experimental and theoretical methods. Specifically, we
studied the influence of different mesosubstituted Co-corroles on
catalytic activity. Using density functional theory (DFT), we computed
lowest unoccupied molecular orbital (LUMO) energies, vertical excitation
energies, electrostatic potentials, and O2 adsorption energies
and compared them with the ORR catalytic activity obtained from cyclic
voltammetry and rotating ring-disk electrode measurements. We found
that the first one-electron reduction for all the corroles occurs
at the Co-center based on computed LUMOs, and that this is a necessary
step for the ORR mechanism to take place. The ORR reduction potential
trends observed from theory and experiments are in good agreement.
Based on this work, we conclude that the role of the substituents
is significant and an important factor that affects the overpotential
required for the ORR.
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