(204k) Atomic-Level Mechanistic Insights into Monolayer hBN Growth from Reactive Molecular Dynamics Simulations for Catalysis Applications

Bin Liu, Mingxia Zhou, Song Liu, and James H. Edgar

Department of Chemical Engineering, Kansas State University, Manhattan, Kansas 66506

Hexagonal boron nitride (hBN) is an important 2D material. Structurally analogous to graphene, hBN is mechanically and chemically stable, and exhibits exceptional optical and electronic properties for applications such as, ultraviolet light emitters, neutron detectors, catalyst supports, and so on. Understanding of the material growth mechanism is one of the key steps towards optimizing and tailoring material synthesis for desired applications.

In this talk, reactive molecular dynamics (MD) simulations – based on the newly developed ReaxFF force field – have been employed to understand the mechanism of hBN growth on nickel substrates. In order to elucidate the growth pathways, NVT-MD simulations, from stoichiometric elemental B and N species deposited onto a Ni substrate, were performed in the temperature range of 1100-1500 K. The elementary nucleation and growth process of a monolayer hBN
structure on the nickel substrate from such elemental B and N sources has been revealed at the atomistic scale: the nucleation initiates from the growth of linear BN chains, which evolve into branched and then hexagonal lattices as the centers for growth. Subsequent DFT calculations are able confirm the energetics of the simulated structure evolution, and also validate the self-consistency within our multiscale modeling framework. Based on the established modeling framework, this talk will also present the recent work further exploring the hBN growth mechanism by varying the stoichiometric ratios of the deposited B and N.

Furthermore, I will also demonstrate - using density functional theory (DFT) calculation - that transition metal (i.e., Pt) catalysts supported on defective hBN monolayer can enhance the activity of CO oxidation reaction. Bader charge analyses were conducted to show that charge transfers associated with the Pt nanoparticles (NPs) bound at the N or B-type vacancies can impact on the binding energies of CO and O₂, on Pt NPs, and thus the reactivity.