This contribution presents a computational account of strong and exothermic interaction of atomic and molecular oxygen with the α(001)B12 surface of boron. Physisorbed oxygen interacts weakly with the surface, but the dissociative chemisorption entails considerable exothermicity in the range of 2.47-3.45 eV, depending on the adsorbed sites of the two oxygen atoms. Nonetheless, rupture of dioxygen on the surface involves a sizable intrinsic reaction barrier of 3.40 eV (at 0 K). Such high amount of energy clearly explains the chemical inertness (i.e., the lack of oxidation) of boron at room temperature. However, elevated temperature encountered in real applications of boron, such as cutting machinery, overcomes the high-energy barrier for the dissociative adsorption of molecular oxygen (3.40 eV). A stability T-P phase diagram reveals the spontaneous nature of the substitutional O/α(001)B12 adsorption modes that lead to the formation of diboron trioxide (B2O3) at temperatures and pressure pertinent to practical applications. This finding conclusively collaborates the experimental observation of the formation of the B2O3 phase from adsorption of oxygen on boron. Finally, charge analysis provides an atomic-scale probe for the predicted stability ordering of the considered O/α(001)B12 configurations.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Physical and Theoretical Chemistry
- Surfaces, Coatings and Films