M-porphyrin (M = Mn, Co) carbon materials as oxygen reduction catalysts from density functional studies

ABSTRACT

The development of high efficient cathode catalyst is known to be very important for the large-scale application of fuel cells. In this work, by using the density functional theory, metal-porphyrin (M = Mn, Co) carbon materials (Mn/CoN₄-C) have been investigated as possible oxygen reduction reaction (ORR) catalysts. The calculated formation energies indicate that Mn/CoN₄-C is stable thermodynamically. For MnN₄-C, ORR proceeds with a four-electron process. While for CoN₄-C, both two-electron pathway and four-electron pathway are competitive, with the former being slightly favoured. For both compounds, the O₂ hydrogenation pathway is favoured compared with O₂ dissociation pathway. In CoN₄-C, the energy barrier is 0.13 eV for the two-electron pathway, while it is 0.47 eV for the four-electron pathway, much lower than 0.80 eV for pure Pt. These energy barriers are also much lower than that in MnN₄-C, showing that CoN₄-C has a better ORR activity than MnN₄-C. The calculated working potential is 0.30 eV for CoN₄ in the four-electron pathway.

GRAPHICAL ABSTRACT

KEYWORDS:

• Oxygen reduction reaction
• reaction mechanism
• metal-porphyrin
• density functional theory

Acknowledgements

Part of the computational time is supported by the Computing Center of Jilin Province and Computing Center of Changchun Institute of Applied Chemistry.

Disclosure statement

No potential conflict of interest was reported by the authors.