Study On The Controllable Preparation Of Bismuth-based Semiconductor Composites And Their Photocatalytic Antifouling Performances

Marine biofouling can be defined as the adverse growth and multiply of some marine organisms on the surface of the engineering facilities in marine environment.Many undesirable effects were caused by marine biofouling,such as serious waste of resources,economic losses,and environmental problems,which have attracted the great attention of researcher for prevention and control of marine biofouling.In the typical formation process of marine biofouling,the formation of biofilm can be considered as a crucial step.In this study,inhibiting the formation of biofilm and killing fouling microorganisms were seen as a starting point to develop new high-efficiency and environmental-friendly marine antifouling and antibacterial materials.Based on the new type bismuth-based semiconductors,three different Z-scheme heterostructured composites were constructed by semiconductor compositing.Pseudomonas aeruginosa(P.aeruginosa)was chosen as the typical marine biofouling microorganism to study the photocatalytic antifouling performance and mechanism of the three composites.The main results are listed as following:(1)Using rectangular sheets-like BiOI as the precursor,Bi₂S₃/BiOI(BSI)Z-scheme heterostructures with excellent photocatalytic properties were successfully prepared via an in-situ ion exchange method on the surface of BiOI nanosheets.A series of BSI composites with large specific surface areas,abundant active sites and broad visible light response range were synthesized by controlling the content of Bi₂S₃ in BSI heterostructures.Based on the study of BSI-1 prepared by different reaction time,the growth mechanism of BSI-1 was proposed.Experimental results indicated that BSI composites exhibited a highly enhanced photocatalytic activity compared to pure BiOI and Bi₂S₃ under visible light irradiation,which can be attributed to the efficient separation of photogenerated electrons(e^-)and holes(h⁺)owing to the formation of stable Z-scheme heterostructure.The rhodamine B(RhB)can be completely degraded and almost all P.aeruginosa can be killed by BSI-1 after visible light irradiation for 60min.Moreover,based on the active species trapping experiments and electron spin resonance(ESR)tests,the·OH,h⁺and·O₂^-radicals were proved as the active species.Furthermore,a possible Z-scheme reaction mechanism was proposed,verifying that the formation of Z-scheme heterostructures played a key role in promoting the separation of photogenerated carriers and enhancing the visible light absorption capacity and photocatalytic performance.(2)Using sheets-like BiOI as the precursor,novel Bi₂MoO₆/BiOI(BMI)Z-scheme heterostructures with excellent visible light photocatalytic properties were successfully prepared via an in-situ ion exchange method on the surface of BiOI.By controlling the content of Bi₂MoO₆ in BMI heterostructures,a series of BMI composites with large specific surface area,many active sites and strong visible light absorption were synthesized.The growth mechanism of BMI was analyzed by controlling the reaction time of BMI-0.5.Experimental results indicated that BMI exhibited a highly enhanced photocatalytic activity compared to pure BiOI and Bi₂MoO₆ under visible light irradiation,which can be ascribed to the efficient transfer and separation of photogenerated charge carriers due to the stable Z-scheme heterostructures.The RhB can be completely degraded and almost all P.aeruginosa can be killed by BMI-0.5under visible light irradiation within 60 min.Moreover,a possible photocatalytic mechanism was proposed based on the active species trapping experiments and ESR tests,verifying that the·OH,h⁺and·O₂^-radicals were the active species.The formation of Z-scheme heterostructures enhances the visible light absorption capacity and promotes the separation of photogenerated carriers.(3)Using MoS₂ with good photocatalytic activities as the precursor,novel Z-scheme MoS₂/Bi₂WO₆(MB)heterostructures with excellent visible light absorption properties were successfully prepared via an in-situ growth on exfoliated MoS₂ nanosheets by a simple hydrothermal method.By controlling the content of MoS₂ in MB heterostructures,a series of MB composites with large specific surface area,many active sites and strong visible light absorption were synthesized.Experimental results indicated that MB exhibited a highly enhanced photocatalytic activity under visible light irradiation compared to pure MoS₂ and Bi₂WO₆,which can be ascribed to the stable Z-scheme heterostructure leading to the efficient transfer and the separation of photogenerated carriers.The photocatalytic degradation efficiency of RhB can reach100%within 90 min and almost all P.aeruginosa can be killed after 60 min by MB-9.Moreover,a possible photocatalytic mechanism was proposed based on the active species trapping experiments and ESR tests,verifying that the h⁺and·O₂^-radicals were the dominating active species,which followed the Z-scheme reaction mechanism.The formation of the Z-scheme facilitated the separation of photogenerated charge carriers,enhanced the visible light absorption capacity and improved the photocatalytic performance.