Preparation Of Bismuth Based Photocatalyst And Study On Photocatalytic Mechanism

Bismuth oxychloride（BiOCl）and bismuth vanadate（BiVO₄）have been extensively studied as new Bi-based photocatalytic semiconductor materials.They all have a more suitable band gap and a higher utilization rate of light.However,the separation efficiency of photogenerated electron-hole pairs of BiOCl and BiVO₄is still low,resulting in low photocatalytic efficiency.In order to improve the above problems,we prepared BiOCl（001）/BiOCl（010）（BB）homogenous in-phase junction to improve the separation efficiency of BiOCl photogenerated electron-holes.Directional doping of Fe³⁺on the（010）crystal plane of BiVO₄improves.The（010）crystal of BiVO₄has the ability to attract electrons.Improve the separation efficiency of photo-generated electrons and holes.Effectively improve the photocatalytic performance of BiOCl and BiVO₄under visible light.The main findings are as follows:The BiOCl sample（B010）with the main exposed crystal plane of（010）and the BiOCl sample（B001）with the main exposed crystal plane of（001）were prepared by the hydrothermal method,and the BiOCl（010）.The sample is the reaction substrate prepared BB homogenous and homogeneous photocatalyst.This heterogeneous composite bismuth oxychloride material degrades 95%of methyl orange solution（10mg/L）in 2.5 h under the condition of Na Cl O₂as a promoter.Characterize the samples by using XRD,SEM,etc.We found that B001 nanosheets were grown on the B010 nanosheets,forming a homojunction BB.Through electrochemical impedance（EIS）analysis,it is found that the in-phase junction BB shows a lower resistance.Compared with the single-component B001 and B010,the homogeneous junction BB sample exhibits stronger photocatalytic activity under simulated sunlight.Through first-principles calculations（DFT）,the energy band structure is explained theoretically.In order to explore the photocatalytic mechanism of BB as a theoretical support.BiVO₄decahedron structure with（010）plane as the main exposed crystal plane was prepared by a simple hydrothermal method.The Fe-BiVO₄photocatalyst was prepared by using the ion substitution method to replace the Bi³⁺ions on the BiVO₄（010）crystal plane with Fe³⁺.We found that the（010）crystal plane of BiVO₄doped with Fe on the surface has a better photocatalytic effect.Under the condition of Na Cl O₂as a promoter,the degradation of methyl orange exceeds 98%in 2.5 hours.The obvious improvement of its photocatalytic performance may be attributed to the following reasons:1.Fe³⁺doping into BiVO₄forms an impurity level in the energy band,which reduces the forbidden band width of BiVO₄and improves its light utilization efficiency.2.The ability of Fe³⁺to obtain electrons is stronger than that of BiVO₄.After doping,it can increase the attracting ability of（010）crystal to electrons and prolong the migration efficiency of photogenerated carriers.It was confirmed by XRD,SEM and XPS that Fe³⁺was indeed doped to the surface of BiVO₄.Finally,the catalytic mechanism of Fe-BiVO₄was theoretically explained through first-principles calculations.