Transitional surface Pt carbide formation during carbon nanotube growth

By correlating structural information with catalytic activity, it is possible to determine the active structure of a catalyst. However, this is far from straightforward and the active structure remains debated even in the well-studied reaction of graphitic carbon formation using noble metal catalysts such as platinum (Pt). One major hindrance is that static observations do not provide access to transitional catalyst states. Here we prove the formation of transitional surface Pt carbide several layers deep as well as a Pt-carbon composite phase during the growth process of carbon nanotubes using atomic-resolution gas in situ transmission electron microscopy combined with density functional theory. Knowledge of the active structure of noble metal Pt is of great interest due to its usage in heterogeneous catalysis. Most importantly, it opens up new avenues to suppress catalyst coking. The unwanted build-up of carbon is the major source of catalyst deactivation in important industrial reactions including propane dehydrogenation, with major financial and environmental consequences.