γ-Graphyne Nanotubes as Defect-Free Catalysts of Oxygen Reduction Reaction: A DFT Investigation
Graphyne materials are potential candidates to fabricate low-cost but efficient metal-free oxygen reduction reaction (ORR) electrocatalysts. However, due to the coexistence of sp and sp2 carbon atoms in graphyne, some factors playing important role in determining ORR activity have received little attention. In present paper, we carried out throughout density functional theory (DFT) calculations to study the curvature effect on ORR activity of γ-graphyne. Our results suggest the (5, 0)-GyNT would be excellent metal-free ORR catalysts. Its limiting potential was computed to be 0.80 V and the number of active sites is up to 16.7%, much better than previously reported CACs. Moreover, it is revealed that the curvature can tune the degree of exposure of p electrons of active site, thus tuning the ORR activity. Our findings are beneficial for further understanding catalytic behavior on graphyne related materials and we suggest a new strategy to design high performance metal-free ORR catalysts.