Understanding of mercury/oxygen reaction mechanism over BiOBr photocatalyst with oxygen vacancy

• Published in: Applied surface science Vol. 664; p. 160244
• Main Authors: Xu, Le, Xu, Jie, Wang, Zhuozhi, Guo, Sheng-Qi
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15.08.2024
• Subjects: Active oxygen species; BiOBr; Oxygen vacancy; Photocatalytic Hg0 oxidation; Quantum chemistry; BiOBr; Active oxygen species; Quantum chemistry; Photocatalytic Hg0 oxidation; Oxygen vacancy
• ISSN: 0169-4332; 1873-5584
• DOI: 10.1016/j.apsusc.2024.160244

[Display omitted] •Hg0 oxidation mechanism over BiOBr photocatalyst was studied by quantum chemistry.•Chemisorbed oxygen shows the higher reactivity than lattice oxygen for Hg0 oxidation.•Oxygen vacancy promotes O2 activation and lowers the energy barrier of Hg0 oxidation.•Oxygen vacancy is retained due to relatively high energy barrier of surface recovery. BiOBr with the advantage of easily generated surface oxygen vacancy, has been considered as a promising photocatalyst for Hg0 oxidation in the flue gas and the active oxygen species is crucial for the oxidation reaction. Nevertheless, the detailed mercury/oxygen reaction mechanism on the BiOBr surface is still unclear and the effect of oxygen vacancy on the reaction process was worth in-depth study. Herein, the oxygen-involved Hg0 oxidation mechanism on the BiOBr surface and the effect of oxygen vacancy were deeply understood by quantum chemistry calculation. The reactivity difference of chemisorbed and lattice oxygen species was revealed. Therein, the chemisorbed oxygen derived from the activation of gaseous O2 molecule showed the higher reactivity than lattice oxygen for Hg0 oxidation reaction. The introduction of oxygen vacancy could promote O2 activation and simultaneously reduce the energy barrier of HgO formation from 1.76 to 1.45 eV. In addition, the energy barrier of oxygen vacancy recovery (0.05 eV) was higher than that of O2 activation (0.02 eV), indicating that the initial oxygen vacancy could be retained in the reaction process. This work deeply revealed the mercury/oxygen reaction mechanism over BiOBr photocatalyst and provided the guidance for the catalyst design in the photocatalytic Hg0 oxidation.