Oxygen Functionalization of Hexagonal Boron Nitride on Ni(111)

Area of Science:

• Surface science
• Materials chemistry
• Catalysis

Background:

• Hexagonal boron nitride (h-BN) is a 2D material with unique electronic and chemical properties.
• Understanding the interaction of 2D materials with reactive gases is crucial for developing new catalysts and electronic devices.
• The adsorption of molecular oxygen on metal surfaces often leads to dissociation, but molecular adsorption is also observed under specific conditions.

Purpose of the Study:

• To investigate the interaction of single-layer h-BN on Ni(111) with molecular oxygen.
• To identify the nature of the adsorbed oxygen species and its bonding characteristics.
• To determine the stability and reaction pathway of the oxygen-functionalized h-BN/Ni(111) system.

Main Methods:

• Supersonic molecular beam epitaxy for controlled oxygen delivery.
• Near-edge X-ray adsorption fine structure (NEXAFS) spectroscopy for electronic structure analysis.
• Temperature-programmed X-ray photoelectron spectroscopy (TP-XPS) for thermal stability studies.
• Density functional theory (DFT) calculations for theoretical insights.

Main Results:

• Formation of a covalently bonded molecular oxygen species, intermediate between superoxide and peroxide.
• Oxygen functionalization is dependent on kinetic energy, with 0.7 eV yielding 0.4 ML coverage.
• Enhanced h-BN to Ni(111) substrate bonding and a shift in valence bands to lower binding energies.
• Oxygen-boron bonds are stable up to ~580 K, followed by desorption and etching of h-BN.

Conclusions:

• The study demonstrates a rare activated adsorption process leading to a stable molecular oxygen adsorbate on h-BN/Ni(111).
• Oxygen functionalization modifies the electronic properties and interfacial bonding of the h-BN layer.
• The findings provide fundamental insights into the reactivity of 2D materials and their interactions with oxygen, relevant for catalysis and materials science.