Transient Kinetic Selectivity in Nanotubes Growth on Solid Co-W Catalyst

Solid Co-W catalysts have been shown to yield single-walled carbon nanotubes (CNT) with high selectivity, simplistically attributed to CNT-catalyst symmetry match for certain chiral indices (n,m). Here, based on large-scale first-principles calculations combined with kinetic Monte Carlo simulations, we show instead that such selectivity arises from a complex kinetics of growth. The solid Co7W6 catalyst strongly favors a restructured, asymmetric CNT edge which entails preferential nucleation of tubes with 2m < n but much faster growth of chiral tubes with n <= 2m. We uncover a tendency or interface defects formation that, although rare, drive CN1 type change rrom smaller to larger chiral angles (zigzag to armchair). Being both least prone to defects and fast growing, the (12,6) CNT appears as a transient, kineticsselected type reaching highest abundance.