Mechanical ball-milling preparation and superior photocatalytic NO elimination of Z-scheme Bi12SiO20-based heterojunctions with surface oxygen vacancies

The creation of n-p heterojunctions with surface oxygen vacancies (OVs) is significant to realize satisfactory photocatalytic performance, thanks to the effective regulation of interface carriers and amplified production of various reactive species. In this study, binary composites Bi 12 SiO 20 /Bi 2 S 3 (BSO-XS) were in situ fabricated via a mechanical ball-milling protocol and subsequently characterized by a battery of analyses. Both anticipated components coexisted and were merged into n-p heterojunctions. Simultaneously, surface OVs were generated along with the decrease of particle size and vulcanization. These composites possessed dramatically strengthened photocatalytic NO annihilation with the diminished generation of NO 2 . After exposure to visible light for 4 min, the best candidate, BSO-0.3S, induced NO removal around 56% and NO 2 formation below 3 ppb, superior to bare components and other composites. The combination of n-p heterojunctions and surface OVs contributed to augmented catalytic capacities through the enhanced visible-light absorption, efficient carriers redistribution and further boosted reactive oxygen-containing species such as ∙OH, ∙O 2 − , and 1 O 2 , the strong affinity of surface OVs to reactants of NO, O 2 , and H 2 O, and favorable energy changes during oxidation reactions, which were sustained by analytical results and density-functional theory (DFT) calculations. A reaction pathway of NO elimination was deduced by in-situ DRIFTS spectra, and a preliminary photocatalysis mechanism was speculated in a Z-scheme model. Such work aims to realize the synergistic effect of Z-scheme n-Bi 12 SiO 20 /p-Bi 2 S 3 heterojunctions and surface OVs over the photocatalytic NO removal and thus provides suitable catalyst candidates for air pollutants removal. Z-scheme composites Bi 12 SiO 20 /Bi 2 S 3 with surface OVs were fabricated using sulfur powder via a facile mechanical ball-milling treatment for the first time, and showed significantly improved NO removal and selectivity for nitrate and nitrite species in comparison to bare Bi 12 SiO 20 , mainly attributing to the enhanced visible-light adsorption by Bi 2 S 3 decoration, efficient carriers redistribution and further boosted reactive oxygen species such as ∙OH, ∙O 2 − , and 1 O 2 , the strong affinity of surface OVs to reactants of NO, O 2 , and H 2 O, and favorable energy changes during oxidation reactions, proven by analytical results and density-functional theory calculations. • N-p heterojunctions Bi 12 SiO 20 /Bi 2 S 3 with surface oxygen vacancies were created via ball-milling. • These composites exhibited significant enhancement of NO removal with the inhibition of toxic NO 2 . • Boosted formation of species ∙OH, ∙O 2 − , and 1 O 2 were cognized by experiments and calculations. • A Z-scheme mode was proposed in photocatalysis mechanism.