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

In the energy conversion context, the design and synthesis of high-performance metal-free carbon nanomaterials with topological defects for the oxygen reduction reaction (ORR) are essential. Herein, we first report a template-assisted strategy to fabricate carbon defect electrocatalysts with rich vacancy coupling pentagons (VP) as active sites in two-dimensional (2D) carbon nanosheets (VP/CNs). Experimental characterizations verify the presence of abundant VP active sites in the VP/CNs electrocatalyst, and the ORR activity is linearly related to the amounts of VP active sites. spectroscopic results identify that the VP/CNs can catalyze direct O-O bond cleavage, bypassing the formation of traditional *OOH intermediates, resulting in the fast kinetics of ORR via a dissociative pathway. The as-prepared VP/CNs show outstanding intrinsic activity for alkaline ORR (half-wave potential of 0.86 V vs reversible hydrogen electrode) with an almost 99% efficiency for four-electron selectivity, outperforming that using the benchmark of Pt/C. Density functional theory calculations further reveal that the cooperative effect between carbon vacancy and adjacent pentagons significantly increases the charge transfer and achieves a lower ORR reaction energy barrier compared with the counterpart of adjacent pentagons or single pentagon. The well-designed carbon defects pave a new avenue for the rational design of metal-free electrocatalysts with high efficiency.