Carbon Dioxide Promotes Dehydrogenation in the Equimolar C 2 H 2 ‐CO 2 Reaction to Synthesize Carbon Nanotubes

The equimolar C 2 H 2 ‐CO 2 reaction has shown promise for carbon nanotube (CNT) production at low temperatures and on diverse functional substrate materials; however, the electron‐pushing mechanism of this reaction is not well demonstrated. Here, the role of CO 2 is explored experimentally and theoretically. In particular, 13 C labeling of CO 2 demonstrates that CO 2 is not an important C source in CNT growth by thermal catalytic chemical vapor deposition. Consistent with this experimental finding, the adsorption behaviors of C 2 H 2 and CO 2 on a graphene‐like lattice via density functional theory calculations reveal that the binding energies of C 2 H 2 are markedly higher than that of CO 2 , suggesting the former is more likely to incorporate into CNT structure. Further, H‐abstraction by CO 2 from the active CNT growth edge would be favored, ultimately forming CO and H 2 O. These results support that the commonly observed, promoting role of CO 2 in CNT growth is due to a CO 2 ‐assisted dehydrogenation mechanism.