Boosting Oxygen Reduction Reaction Kinetics by Designing Rich Vacancy Coupling Pentagons in the Defective Carbon

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• High-performance metal-free carbon nanomaterials are crucial for energy conversion, particularly for the oxygen reduction reaction (ORR).
• Topological defects in carbon nanomaterials can significantly influence their catalytic activity.

Purpose of the Study:

• To design and synthesize novel two-dimensional (2D) carbon nanosheets (VP/CNs) with vacancy coupling pentagons (VP) as active sites.
• To investigate the structure-activity relationship of VP/CNs in the oxygen reduction reaction (ORR).

Main Methods:

• Template-assisted synthesis strategy was employed to fabricate VP/CNs.
• Experimental characterizations (e.g., in situ spectroscopy) were used to verify active sites and reaction mechanisms.
• Density functional theory (DFT) calculations were performed to understand the electronic properties and reaction pathways.

Main Results:

• VP/CNs electrocatalysts with abundant VP active sites were successfully synthesized.
• ORR activity showed a linear correlation with the density of VP active sites.
• VP/CNs demonstrated direct O-O bond cleavage, enabling fast ORR kinetics via a dissociative pathway.
• The synthesized VP/CNs exhibited excellent intrinsic activity for alkaline ORR (half-wave potential of 0.86 V vs RHE) with 99% four-electron selectivity, surpassing commercial Pt/C.
• DFT calculations revealed that the cooperative effect between carbon vacancy and adjacent pentagons enhances charge transfer and lowers the ORR energy barrier.

Conclusions:

• The developed VP/CNs serve as highly efficient metal-free electrocatalysts for ORR.
• The rational design of carbon defects, specifically VP sites, offers a promising strategy for developing advanced electrocatalysts.
• This work paves a new avenue for designing high-performance metal-free electrocatalysts for energy conversion applications.