Ligand substitution effects in metallo corroles: Improvements in theoretical prediction

Metallocorroles (M-N-C) and especially cobaltcorroles are some of the best alternatives to the expensive platinum-group metals (PGM) for oxygen reduction reaction (ORR) catalysis in polymer electrolyte membrane (PEM) fuel cells [1, 2]. Recent study has discovered that the M-N-C corroles based on Mn may also be a good alternative catalyst [3] but require improvement with regard to their catalytic efficiency. We study the M-N-C corroles with M= Mn, Fe, Co, Ni, Cu, and the ligand (L) substitution (L-M-N-C, L = H, CH3, CF3, and imidazole) on the metal site using density functional theory calculations. Following the well-known ORR pathway, we calculate the free energies of the *OOH, *O and *OH intermediates. In particular, we examine the magnetic states of the intermediates that has not been investigated in previous work. We perform calculations using different exchange-correlation functionals and different solvent environments including gas phase, and water and acetonitrile solvents. We find that better catalytic efficiency is expected in ligand substituted Mn-N-C that can be further fine-tuned by changing the nature of the ligand. We hope that this work will motivate further experimental work on Mn-N-C PGM-free catalysts for ORR catalysis in PEM fuel cells.

References:

1. Angew. Chem., Int. Ed. 54, 14080-1408 (2015)

2. J. Phys. Chem. C 122, 17686-17694 (2018)

3. Nature Catalysis 1, 935-945 (2018)