Study On Farication Of Bismuth Oxyiodide Composite Photocatalysts And Their Photocatalytic Properties

Bismuth oxyiodide is widely used in photocatalysis,photoelectrocatalysis and other fields due to its good visible light response and low cost,etc.However,some shortcomings included the seriously recombination of photo-generated electrons and holes in bismuth oxyiodide resulting in limited its photocatalytic performance.Therefore,in this paper,Z-scheme BiOI/Ag/PANI heterojunctions,the bismuth-rich Bi₄O₅I₂ composites modified metal Bi and oxygen vacancies were prepared respectively by constructing Z-scheme heterojunctions,metal loading and oxygen vacancy introduction.The main contents are as follows:（1）A Z-scheme BiOI/Ag/PANI（BAP） heterojunction was successfully constructed by embedding Ag nanoparticles at the interface of the type-Ⅱ BiOI/PANI（BP）heterojunction.It was found that the BAP-10 sample exhibited the best photoelectrocatalytic（PEC） efficiencies for degradation of RhB and reduction of Cr（Ⅵ）,the kinetic constants of which were approximately 5 and 12 times respectively higher than those of type-Ⅱ BP,6 times and 1.7 times respectively higher than those of pure BiOI.This was attributed to enhanced charge separation efficiency and stronger redox capacity of the Z-scheme mechanism and the excellent light absorption efficiency from the surface plasmon resonmance（SPR） effect of Ag.The results of photocurrent response and the time-resolved photoluminescence spectra proved that the separation efficiency of photo-generated carriers of BAP-10 was higher than that of BP and BiOI.Importantly,electron spin resonance and terephthalic acid photoluminescence probing technique confirmed that BP presented type-Ⅱ and BAP presented Z-scheme heterojunction mechanism.The charge transfer pathways of Z-scheme were further studied by linear-sweep voltammogram and surface photovoltage spectra.The work not only provided an excellent reference for rationally converting the type-Ⅱ to the Z-scheme heterojunction but also revealed the charge transfer mechanism of the Z-scheme.（2）The content of metal Bi was regulated along with the generation of oxygen vacancies in the bismuth-rich Bi₄O₅I₂ via a one-pot solvothermal method,by adjusting the volume ratio of the solvent ethylene glycol to glycerol based on the characteristics that glycerol has higher viscosity and hydroxyl content than ethylene glycol.The experimental results showed that as the amount of glycerol was increased,the more metal Bi were formed in situ on the Bi₄O₅I₂ microspheres.When the volume ratio of ethylene glycol to glycerol was 1:5,the as-prepared Bi-Bi₄O₅I₂-3 exhibited the best photocatalytic degradation performance over levofloxacin（LEV）,and the degradation rate of LEV reached 88.0% in 60 minutes,attributing to the enhanced light absorption capacity and the improved separation efficiency of photo-generated electrons and holes benefited from the SPR effect with a proper amount of metal Bi and the defect states of oxygen vacancies in the composite.The research revealed that Bi-Bi₄O₅I₂-3 has excellent photocatalytic adaptability and cyclic stability.