Boosted photocatalytic NO removal performance by S-scheme hierarchical composites WO3/Bi4O5Br2 prepared through a facile ball-milling protocol

It is crucial to develop an efficient system of high photocatalytic capability over NO removal and simultaneous avoidance of toxic NO2 formation. In this study a serious of hierarchical composites WO3/Bi4O5Br2 (WB) were successfully fabricated by a facile ball-milling protocol and systematically characterized by various analytical techniques. Both expected ingredients were realized and coexisted in composites to generate heterojunction structures by microstructural analyses. Under visible light irradiation, these samples were exposed to photo catalytic removal of NO measurements, where aforementioned binary hierarchical WB composites showed reinforced NO removal efficiency with the high selectivity for NO3-/NO2- species in comparison to bare WO3 and Bi4O5Br2, mainly associating to the efficient migration and spatial segregation of charge carries through heterojunction domains with suitable phase composition instead of the slightly varied visible light absorption and specific surface area. In addition, a possible photocatalysis mechanism was deduced in a S-scheme model by active species determination and band structures estimation of these robust catalysts. This investigation shed light on the facile fabrication of hierarchical composites via the ball-milling treatment with enhanced photo catalytic removal of low concentration NO in ppb level under visible light.