The diffusive nature of Au and the Pt clusters supported on various carbon nanotubes was studied through molecular dynamics simulation (table 2). It was found that the cluster/carbon nanotube interface was essential and the matching between the diffusion pathways on the carbon nanotubes and the linear atomic arrangements of the bottom layer of the clusters controlled the diffusion behavior of the clusters. The atomic arrangement of the cluster bottom layer was independent of the kind of carbon nanotubes. The direction and the gap of the diffusion pathways on the carbon nanotubes were however quite dependent on the chirality and radius of the carbon nanotubes. Based upon careful investigations, a strategy was proposed for minimizing the aggregation of carbon nanotube-supported nanoclusters that worsened the catalytic properties.
Molecular Dynamics Simulation of the Diffusion of Au and Pt Nanoclusters on Carbon Nanotubes. Seo, D.H., Kim, H.Y., Ryu, J.H., Lee, H.M.: Journal of Physical Chemistry C, 2009, 113[24], 10416-21
Table 2
Diffusion rates of Au and Pt clusters on C nanotubes
Nanotube | Diffusant | Coefficient | Value (cm2/s) |
(8,0) | Au | com | 3.10 x 10-5 |
(8,0) | Au | circumferential | 2.27 x 10-5 |
(8,0) | Au | axial | 4.79 x 10-5 |
(8,0) | Pt | com | 2.66 x 10-5 |
(8,0) | Pt | circumferential | 3.32 x 10-5 |
(8,0) | Pt | axial | 1.33 x 10-5 |
(5,5) | Au | com | 1.38 x 10-5 |
(5,5) | Au | circumferential | 1.85 x 10-5 |
(5,5) | Au | axial | 0.44 x 10-5 |
(5,5) | Pt | com | 2.24 x 10-5 |
(5,5) | Pt | circumferential | 2.93 x 10-5 |
(5,5) | Pt | axial | 0.85 x 10-5 |
(24,0) | Au | com | 0.40 x 10-5 |
(24,0) | Au | circumferential | 0.29 x 10-5 |
(24,0) | Au | axial | 0.60 x 10-5 |
(43,0) | Au | com | 0.12 x 10-5 |
(43,0) | Au | circumferential | 0.08 x 10-5 |
(43,0) | Au | axial | 0.19 x 10-5 |
(24,0) | Pt | com | 2.07 x 10-5 |
(24,0) | Pt | circumferential | 1.75 x 10-5 |
Table 2 (continued)
Diffusion rates of Au and Pt clusters on C nanotubes
Nanotube | Diffusant | Coefficient | Value (cm2/s) |
(24,0) | Pt | axial | 2.69 x 10-5 |
(43,0) | Pt | com | 1.82 x 10-5 |
(43,0) | Pt | circumferential | 0.74 x 10-5 |
(43,0) | Pt | axial | 3.99 x 10-5 |
(15,15) | Au | com | 1.24 x 10-5 |
(15,15) | Au | circumferential | 1.36 x 10-5 |
(15,15) | Au | axial | 1.01 x 10-5 |
(25,25) | Au | com | 0.72 x 10-5 |
(25,25) | Au | circumferential | 0.25 x 10-5 |
(25,25) | Au | axial | 1.67 x 10-5 |
(15,15) | Pt | com | 1.17 x 10-5 |
(15,15) | Pt | circumferential | 0.99 x 10-5 |
(15,15) | Pt | axial | 1.54 x 10-5 |
(25,25) | Pt | com | 1.52 x 10-5 |
(25,25) | Pt | circumferential | 0.74 x 10-5 |
(25,25) | Pt | axial | 3.09 x 10-5 |
com = cluster centre-of-mass