Stepwise Oxidation Mechanisms of <i>h</i> ‐BN: Effect of Zigzag Edge and Armchair Edge

ABSTRACT Hexagonal boron nitride ( h ‐BN) exhibits exceptional thermal stability and chemical inertness, enabling versatile applications in harsh environments. However, under high‐temperature conditions, h ‐BN undergoes oxidation, leading to material degradation and limiting its practical utility. This study investigates the oxidation mechanisms of h ‐BN using density functional theory (DFT) calculations at the generalized gradient approximation (GGA) level with the Perdew–Burke–Ernzerhof (PBE) functional. The results reveal that O 2 molecules dissociate more readily at Zigzag edges of h ‐BN with a low activation energy of 0.04 eV, while at the Armchair edges, this dissociation requires a higher activation energy of 0.60 eV. The stepwise oxidation of Zigzag‐BN and Armchair‐BN reveals that the oxidation primarily proceeds through continuous oxidation in Zigzag‐BN that disrupts planar structure and breaks the six‐membered BN rings, whereas the continuous oxidation mainly targets the six‐membered BN rings in Armchair‐BN. Once oxygen adsorbs and weakens the B─N bonds, N atoms removal becomes energetically more favorable. The oxidation products exhibit distinct structural features: Zigzag edges generate ring‐island B 2 O 3 , whereas Armchair edges produce chain‐like B 2 O 3 . These findings provide fundamental atomic‐level insights into the intrinsic oxidation and edge‐specific reactivity of h ‐BN, establishing a theoretical foundation for future defect control and selective passivation strategies against high‐temperature oxidation.