Temperature dependence of catalytic activity in graphene synthesis for Sn nanoparticles

Graphene synthesis at lower temperatures is quite important for a wider range of practical applications. Sn, which is recently found as a promising catalyst for the low-temperature graphene growth, is taken as the study material in this work. Based on the detailed transmission electron microscopy (TEM) observation, we found that catalytic activity of Sn nano-particles is highly temperature dependent which was observed during graphitization of amorphous carbon. For this study, C–Sn composite nanofibers were prepared on an edge of a carbon foil by the Ar⁺ ion irradiation with simultaneous supply of Sn. As-fabricated C–Sn composite nanofibers were observed to be the amorphous C nanofibers (CNFs) in which the Sn nanoparticles dispersed. The as-prepared samples were annealed at 180–250 °C in a vacuum and were characterized using Raman spectra and high-resolution TEM to study the graphitization process. The graphitization started to occur at an annealing temperature of 180 °C, which is much lower than the graphitization temperature for bulky Sn. Based on the detailed TEM observation of annealed samples, a model to explain the graphitization mechanism at such a low temperature was proposed.