Interfacial oxidation of boron proceeds through a stable B₆O intermediate

The oxidation of boron (B) is of great significance in catalysis, metallurgy, corrosion, and combustion. However, understanding the early stages of oxidation and identifying intermediate phases remain a long-standing challenge. Here we reveal an oxidation mechanism termed the W-J model; unlike classical models that rely on the diffusion of oxygen or boron through a B₂O₃ layer, the initial reaction in the W-J model takes place at the interface between the boron core and the B₂O₃ shell. This interfacial reaction produces an oxidized intermediate, B₆O, which is then further oxidized to form B₂O₃. The formation of B₆O plays a crucial role in regulating the oxidation process. Its high thermal stability and strong oxygen affinity act as barriers to continuous oxidation, thereby lowering the ignition and combustion efficiency of boron. These findings highlight a fundamentally different reaction pathway that may help explain the limited reactivity observed in practical applications.