Regulating Electron Transfer Number and Catalytic Activity via Nitrogen-Doping in Graphdiyne for Electrochemical Oxygen Redox Reactions

Developing nitrogen-doped carbon materials (NCMs) with high catalytic activity and selectivity is crucial for advancing energy technologies. However, the contradictory effects of nitrogen doping on the intrinsic properties of hexagonal aromatic ring systems have hindered mechanistic research and materials design. Herein, we leverage graphdiyne (GDY) as a platform to design three distinct nitrogen-containing monomers, enabling the preparation of NCMs with precisely defined nitrogen configurations (triazinic-N in tz-GDY, pyrazinic-N in pz-GDY, and pyridinic-N in py-GDY). This approach ensures atomic-level control over nitrogen speciation and structural clarity, effectively addressing the challenge of multiple nitrogen species coexisting in conventional NCMs. The results demonstrate that tz-GDY exhibits superior bifunctional activity in oxygen redox reactions, with an electron transfer number of 3.21 in the oxygen reduction reaction (ORR) compared to 2.45 for pz-GDY and 2.20 for py-GDY. Density functional theory (DFT) calculations reveal that the progressively stronger electron-withdrawing effect from pyridinic-N (py-GDY) to pyrazinic-N (pz-GDY) to triazinic-N (tz-GDY) accounts for the variations in the ORR electron transfer number and overall catalytic performance. This research provides a comprehensive mechanistic understanding of nitrogen doping in hexagonal aromatic carbon materials for oxygen redox reactions and highlights GDY's exceptional potential as a molecular-level design platform for advanced electrocatalysts.