Augmented photocatalytic NO removal by the S-scheme Bi7O9I3/Bi2S3 heterojunctions with surface oxygen vacancies: Experimental analyses and theoretical calculations.

The establishment of S-scheme heterojunctions represents an effective strategy for enhancing the transfer and separation of charge carriers, thereby bolstering redox capacities and consequently benefiting subsequent photocatalytic reactions. In this study, the pristine Bi7O9I3 underwent a facile vulcanization process to in-situ produce various composites. Systematical characterizations confirmed the simultaneous generation of Bi7O9I3/Bi2S3 (BI-BS) heterojunctions with surface oxygen vacancies (OVs). Under visible light, these BI-BS composites exhibited improved NO removal efficiencies with reduced NO2 generation compared to bare Bi7O9I3. Particularly, the best candidate BI-BS2 possesses the highest NO removal (43.02%) and lowest NO2 generation (5.44%) among all tested samples. The improvement was primarily attributed to synergetic effects of heterojunction and surface OVs, including enhanced charge separation, heightened light responsiveness, and improved generation of reactive oxygen-containing species through an S-scheme mode. Furthermore, the Density Functional Theory (DFT) calculations had demonstrated that the establishment of BI-BS heterojunctions with surface OVs not only optimized the electronic structure to facilitate the transfer and separation of charge carriers, but also significantly enhanced the adsorption of NO, H2O, and O2 molecules, ultimately favoring the generation of NO3- species. These as-synthesized composites indicated sufficient structural stability and hold potential for the photocatalytic removal of NO at ppb levels.

The Strengthened Photocatalytic NOx Removal of Composites Bi4O5Br2/BiPO4: The Efficient Regulation of Interface Carriers by Integrating a Wide-Bandgap Ornament.

A series of binary composites Bi4O5Br2/BiPO4 (PBX) was fabricated through a simple mechanical ball milling protocol. Relevant microstructural, morphological, and optical properties were thoroughly analyzed via various techniques. The integration of both components was confirmed to produce heterojunction domains at the phase boundaries. Upon exposure to visible light irradiation, the as-achieved PBX series possessed the reinforced photocatalytic NOx removal efficiencies and the weakened generation of toxic intermediate NO2 in comparison to both bare components, chiefly attributed to the efficient transport and separation of carriers and boosted production of superoxide radicals (·O2-) through the combination of a wide-bandgap ornament BiPO4 as an electron acceptor. In particular, the composite PB5 with the optimal phase composition exhibited the highest NOx removal of 40% with the lowest NO2 formation of 40 ppb among all tested candidates. According to the band structures' estimation and reactive species' detection, a reasonable mechanism was ultimately proposed to describe the migration of charge carriers and the enhancement of photocatalytic performance.