Why Do Boron and Nitrogen Doped α- and γ-Graphyne Exhibit Different Oxygen Reduction Mechanism? A First-Principles Study

The oxygen reduction reaction mechanisms catalyzed by B, N doped alpha- and gamma-graphyne were investigated in detail by DFT methods, in which doped graphynes with different configurations could exhibit different oxygen reduction reaction activities. The B or N single-doped alpha-B(1)G and a-N(2)G and co-doped alpha-B(1)N(2)G and alpha-B(1)N(3)G show relatively low catalytic activities, owing to their unfavorable reversible potential in oxygen reduction steps, while the co-doped alpha-B(1)N(4)G with separated B, N and single-doped gamma-NG show relatively high activities. With the further increasing of the N content, the onset potential is largely enhanced to 0.413 V for alpha-B-1(N-4)(3)G. The origin of activity of alpha-B-1(N-4)(3)G and gamma-NG is attributed to the higher energy levels of the highest occupied molecular orbital and/or more positive charge (spin) density distributions.