The Investigation For Preparation And Properties Of BiOI-based Composite Photocatalysts

The photocatalysis technology has shown larger potential in the field of environmental purification and clean energy production due to its utilization of clean and pollution-free solar energy.BiOI exhibits good visible light photocatalytic performance due to its narrow band gap.However,the narrow band gap also leads to a high recombination rate of photogenerated electrons and holes which limited its application in photocatalysis.Herein,the preparation of BiOI-based composites and the construction of their composite structure were investigated.The efficient separation ability of photogenerated electrons and holes significantly enhanced the photocatalytic performance.The research contents in this paper are as follows:（1）The electrostatic induced self-assembly method was applied to prepare core-shell hierarchical structure of BiOI/OMCMB（Oxidized mesocarbon microbead）composites（MB）,in which BiOI nanosheets were uniformly immobilized on the surface of OMCMB.The graphite carbon OMCMB played a crucial role in inducing and assembling the core-shell structure of the MB composites,which effectively improved the conductivity of the catalyst,promoted the photogenerated charge separation and enhanced the photocatalytic performance of BiOI.The sample MB-3could degrade 96.8%tetracycline hydrochloride（TH）under the visible-light irradiation for 60 min.MB-3 remains favorable photocatalytic activity after four cycles.（2）The flower spherical BiOI/Bi₅O₇I heterojunction（BBOI）was fabricated using the bacitracin as the template.The introduction of bacitracin can regulate the formation and assembly of flower spherical with cross-linked nanosheet structure.Specially,the dosage of bacitracin can control the thermal conversion of BiOI to Bi₅O₇I.The in-situ partial conversion of BiOI caused the formation of the intimate S-scheme heterojunction interface between BiOI and Bi₅O₇I,which can efficiently promote the separation and migration of photogenerated carriers.Consequently,the BBOI exhibited enhanced photocatalytic performance in terms of photocatalytic reduction of Cr（Ⅵ）simultaneous oxidative degradation of TH.Under visible light for 60 min irradiation,the reduction rate of Cr（Ⅵ）and the degradation rate of TH by BBOI-3 were 100%and80.0%,respectively.And it still displayed the favorable redox capacity after four cycles.（3）The Bi₅O₇I/Bi₄Ti₃O₁₂（BOI/BTO）photocatalysts were fabricated by in situ grown method.The BOI and BTO have abundant interface contact and constructed a Z-scheme heterojunction structure of BOI/BTO composite.These composites exhibited excellent performance for selective oxidation of benzylic alcohols under the visible light,which was attributed to the stronger absorption capacity of visible light and the high separation efficiency of photogenerated carriers via the Z-scheme transfer mechanism.The sample BOI/BTO-1.5 achieved 92.4%selectivity for oxidation of 4-methylbenzyl alcohol to 4-methyl-benzaldehyde in the presence of H₂O₂,which also exhibited good stability,reusability and substrate adaptability.As evidenced by the activity experiments,trapping experiments and ESR analysis,the·O₂^-radicals and·HOO radicals were the main active species directly involved in the photocatalytic oxidation process.