Oxygen vacancies-modified S-scheme heterojunction of Bi-doped La₂Ti₂O₇ and La-doped Bi₄Ti₃O₁₂ to improve the NO gas removal avoiding NO₂ product

Monoclinic phase La₂Ti₂O₇ and orthorhombic phase Bi₄Ti₃O₁₂ with layered crystal structure constructed by the perovskite slab were widely used in photocatalysis. Their electronic structures are the most crucial factor in high photocatalytic activity. Bi-doped La₂Ti₂O₇ gradually converts to La-doped Bi₄Ti₃O₁₂ with the incorporation of bismuth ions, and the two phases build an S-scheme heterojunction. More oxygen vacancies were introduced into the S-scheme heterojunction after heat treatment in a nitrogen atmosphere. The 0.1BTO/LTO-OV sample exhibits the largest NO removal efficiency of 52% and only 5.6 ppb NO₂ intermediate generation. The improved NO removal efficiency was ascribed to the synergistic effect of oxygen vacancies, doping and heterojunction, providing a new insight into the photocatalytic NO removal. The photocatalytic mechanism was eventually proposed on the basis of trapping experiments.