Enhancement of Nitrogen Reduction Reaction Activity of sp-B-doped γ-Graphyne Nanotubes through Curvature Effect

Developing novel, metal-free materials as efficient catalysts for the electrochemical nitrogen fixation reaction (NRR) to replace the Haber-Bosch process remains a significant challenge. Herein, γ-graphyne nanotubes (γGyNTs) doped with single sp2-B or sp-B were developed as electrocatalysts. The NRR activity of the doped γGyNTs was studied by intensive density functional theory (DFT) calculations. The results reveal that the curvature effect significantly enhances the catalytic activity of sp-B-doped γGyNTs, in contrast with that achieved via sp2-B doping. The limiting potential of sp-B-doped (2, 0)-γGyNT is predicted to be −0.071 V, which is significantly superior to that of previously reported metal-free catalysts (MFCs). Moreover, the competing hydrogen evolution reaction (HER) is suppressed by sp-B-doped (2, 0)-γGyNT. Analysis of the catalytic mechanism revealed that the enhanced NRR activity of the sp-B doped γGyNTs mainly originates from the synergistic effects of the enhanced exposure of the p-orbital and positive charge on the sp-B dopants induced by the curvature effect, which can alter the interactions with intermediates. The present findings are insightful and suggest a new strategy for designing graphyne-related materials as high-performance non-metallic NRR catalysts.