IT-7-P-6127 In situ observations of confined platinum nanoparticles coalescing within carbon nanotubes

Carbon nanotubes (CNT) in which the core is filled with a metal are receiving increased attention due to their potential application in catalysis [1], and electronic devices [2]. Moreover, the structural and chemical properties of metals inside CNT can be different as compared to their bulk counterparts. For example, metal residing inside CNT usually show enhanced catalytic performance than CNT decorated with metal nanoparticles [3]. In the specific case of platinum filled CNT (Pt@CNT) they can show higher hydrogenation activity, enantioselectivity and average turnover frequency than CNT with surfaces decorated with Pt NPs.

When using nanoparticles for catalytic purposes it is crucial to stabilize the nanoparticles, because coalescence is the main cause of their catalytic deactivation. The details of these processes in a confined environment, for example, inside a CNT have not yet been explored. This work focuses on an in-situ study of Pt nanoparticles inside carbon nanotubes using Cs aberration corrected TEM with an acceleration voltage of 80 kV. The confined environment of the CNT restricts the freedom of movement for the Pt nanoparticles compared to non-confined reactions. The study shows the various processes during coalescence of Pt nanoparticles which can occur via particle reorientation, relaxation and direct attachment of atoms on the surface. In addition, we find many Pt nanoparticles have their (111) plane parallel to the tube wall which might suggest preferential alignment.