(228g) Preparation of Functional Hexagonal Boron Nitride and Its Catalytic Applications

Hexagonal boron nitride (hBN) is a unique 2D functional material. Mechanically and chemically stable, hBN also exhibits exceptional optical and electronic properties for ultraviolet light emitter, and neutron detector applications. Opportunities to incorporate hBN into various catalytic materials are being explored as well.

To understand the hBN growth mechanism on transition metal substrate (e.g., Ni) is an important step toward controlling the shape, edge termination, and lattice defects for catalytic applications. Reactive molecular dynamics simulations using the ReaxFF force field were performed to gain molecular insights into this highly reactive and complex process. The simulation trajectory revealed that hBN nucleation initiates from the growth of linear BN chains, and then evolves into branched and then hexagonal lattices as the center of growth. We also showed that the hBN domain geometries are influenced by the chemical potentials of N and B sources. System N plays a more crucial role in dictating the size of hBN lattices. With an increase of the N:B ratio, the shapes of hBN domain transition from equilateral triangles to hexagons.

Two catalytic applications based on monolayer hBN were studied. First, Pt catalysts supported on defective hBN monolayer were studied to understand the enhancement of CO oxidation reaction. Bader charge analyses showed that charge transfers associated with the Pt nanoparticles bound at the N or B-type vacancies can impact on the binding energies of CO and O₂ on Pt, and thus, the catalyst reactivity.

More recently, the electronic structures of g-C₃N₄ hetero-bilayers paired with hBN monolayers were evaluated using Density Functional Theory (DFT) as a potential oxygen reduction reaction (ORR) electrocatalyst. It has been shown that the hBN sublayer, without direct contact, can still modulate the electronic structures of the g-C₃N₄ top layer to influence its interactions with ORR reaction intermediates.