Oxygen vacancy-induced efficient photocatalytic antifouling activities of Bi5O7I microspheres on marine concrete

Abstract

Bi5O7I photocatalysts are considered potentially excellent marine antifouling materials. However, the photocatalytic properties differ for Bi5O7I photocatalysts with various morphologies, and the photocatalytic mechanisms involved remain unclear. In addition, powdered Bi5O7I photocatalysts are difficult to work with in an exact manner on marine structure surfaces, such as concretes, in actual marine environments. Thus, in this study, Bi5O7I photocatalysts with various morphologies comprising nanosheets, nanorods, nanoflowers, and microspheres (MS) were successfully synthesized. Among these Bi5O7I photocatalysts, the highly regular Bi5O7I MS (Bi5O7I-MS) were found to have the highest photocatalytic properties in both the degradation of Rhodamine B and inactivation of bacteria. This strong photocatalytic ability can be attributed to the high specific surface area and rich oxygen vacancies (OVs) in Bi5O7I-MS. The possible photocatalytic mechanism involves h+ playing the major role, with ∙OH and ∙O2− partially contributing to the photocatalytic process. OVs also promoted the photocatalytic properties of Bi5O7I-MS by trapping photoinduced electrons to accelerate the photocatalytic process. Furthermore, Bi5O7I-MS photocatalysts were successfully grown in situ on cement mortar surfaces, where they showed extremely high antifouling performance, with hardly any living bacteria attached. These findings clarify the morphology-dependent mechanism associated with Bi5O7I photocatalysts, as well as facilitating the growth of photocatalysts in situ on cement mortar for applications in marine antifouling.