Visible light driven BiOBr/ZIF-67 S-scheme heterojunction as a novel effective marine biofouling inhibitor

Effective and economical marine biofouling protection methods are facing great challenges given the requirements of environmental friendliness and efficiency. Inspired by this, a novel BiOBr/ZIF-67 S-scheme heterojunction photocatalyst with core-shell structure was successfully synthesized by a facile in-situ growth method, where ZIF-67 was uniformly and firmly anchored on the surface of BiOBr microspheres. BiOBr/ZIF-67 composites exhibited excellent removal efficiencies towards typical marine fouling bacteria and microalgae compared with pure ZIF-67 and BiOBr, including Staphylococcus aureus, Escherichia coli, Chlorella sp., and Phaeodactylum tricornutum. The excellent photocatalytic antifouling performance can be ascribed to the formation of core-shell structure and S-scheme heterojunction, leading to the larger relative surface area, broader visible light response, and enhanced charge separation efficiency. Moreover, a possible photocatalytic mechanism of BiOBr/ZIF-67 S-scheme heterojunction was proposed based on electron spin resonance (ESR) tests, validating the major roles of active species such as ·OH, ·O2-, h+, and 1O2 to attack microorganisms during the photocatalytic process. The density functional theory (DFT) simulated calculations further elucidated the formation of S-scheme heterojunction and the transfer path of electrons and holes in the contact interface. More importantly, a prospective attempt was made by adding BiOBr/ZIF-67 composites into a silicone-based coating to form an antifouling-enhanced coating, presenting a high antibacterial rate and the potential application prospect in marine antifouling. This work provides new insights into fabricating high-performance S-scheme heterojunction photocatalysts for marine antifouling applications.