A density functional theory study on oxygen reduction reaction on nitrogen-doped graphene

Area of Science:

• Electrochemistry
• Materials Science
• Computational Chemistry

Background:

• Nitrogen (N)-doped carbons are recognized for their electrocatalytic potential in fuel cell oxygen reduction reactions (ORR).
• Understanding the precise ORR mechanism on N-doped graphene is crucial for optimizing fuel cell performance.

Purpose of the Study:

• To provide theoretical insights into the oxygen reduction reaction (ORR) mechanism on nitrogen-doped graphene.
• To investigate and compare the energetic favorability of different ORR pathways.

Main Methods:

• Density functional theory (DFT) calculations were employed to explore all possible reaction pathways.
• Transition states for each elementary step of the ORR mechanism were identified.

Main Results:

• The reduction of hydroperoxyl (OOH) species was found to be energetically more favorable than the breaking of the O-OH bond.
• A direct Eley-Rideal mechanism for OOH reduction, with a low reaction barrier of 0.09 eV, was identified.
• Both two-electron and four-electron ORR pathways are possible, with distinct rate-determining steps.

Conclusions:

• The two-electron ORR pathway is energetically favored over the four-electron pathway due to lower activation barriers.
• The findings suggest that N-doped graphene can efficiently catalyze ORR, with specific mechanisms identified for optimization.