On the Evolution of Pt Nanoparticles on Few-Layer Graphene Supports in the High-Temperature Range

Controlling the size, dispersion, and shape of nanoparticles (NPs) in the high-temperature range is a key topic for the development of new technologies with applications in the particular fields of catalysis and energy storage. In this article, we present an approach combining in situ transmission electron microscopy (TEM), electron tomography (ET), and molecular dynamics (MD) calculations for assessing the evolution of Pt NPs deposited onto few-layer graphene supports. Spherical Pt NPs with average sizes of 2 nm located preferentially at the support topographical defects (e.g., steps and edges) diffuse and coalesce along these defects, such that, after annealing to 700 degrees C, the nanoparticles were located exclusively here. Their dispersion remained significant; only the particle size distribution changed from mono- to bimodal. This statistical variation is discussed herein by reviewing fundamental issues such as the NP-support interaction and NP faceting, diffusion, and subsequent sintering in the high-temperature range. Fundamental MD simulations are reported here as reinforcements of the experimental findings and as a means to provide deeper insight into the phenomenological issues behind the behavior of the system investigated.