Jointly augmented photocatalytic NO removal by S-scheme Bi12SiO20/Ag2MoO4 heterojunctions with surface oxygen vacancies

The deep oxidation of NO molecules to NO3– species with the avoidance of toxic NO2 generation is a big and challengeable concern, which can be solved by the rational design and construction of catalytic systems with satisfactory structural and optical features. For such, in this investigation binary composites Bi12SiO20/Ag2MoO4 (BSO-XAM) were fabricated through a facile mechanical ball-milling route. From microstructural and morphological analyses, heterojunction structures with surface oxygen vacancies (OVs) were simultaneously created, contributing to the enhanced visible-light absorption, reinforced migration and separation of charge carries, and further boosted generation of reactive species such as superoxide radicals and singlet oxygen. Based on the density-functional theory (DFT) calculations, surface OVs induced the strengthened adsorption and activation of O2, H2O, and NO molecules and oxidation of NO to NO2, while heterojunction structures were beneficial for the continuous oxidation of NO2 to NO3– species. Thus, the heterojunction structures with surface OVs synergistically guaranteed the augmented photocatalytic NO removal and constrained NO2 generation of BSO-XAM through a typical S-scheme model. This study may provide scientific guidances for the photocatalytic control and removal of NO at ppb level by Bi12SiO20-based composites through the mechanical ball-milling protocol.